A high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloy, a preparation method, a magnesium alloy melt purifying method, and a magnesium alloy component manufacturing method

Abstract

The present application belongs to the technical field of magnesium alloy melt purification, and particularly relates to a high-efficiency purification agent for low-aluminum semi-solid injection magnesium alloy, a preparation method, a magnesium alloy melt purification method and a magnesium alloy component manufacturing method. The purification agent comprises a core purification component, an auxiliary purification component and a microcapsule coating component. The present application adopts a rare earth-alkaline earth metal chloride-fluoride composite molten salt system and a coaxial electric spray microcapsule coating technology, and designs a purification agent for the semi-solid interval. The purification agent not only avoids the problem of re-oxidation caused by cooling after liquid purification, but also realizes in-situ purification in the semi-solid interval for the first time. In addition, the multi-mechanism synergistic purification system provided by the present application can adapt to the purification needs of different types of low-aluminum magnesium alloys such as AZ series, AM series and AS series, and has wide universality and excellent purification effect.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy melt purification technology, specifically relating to a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloy, its preparation method, a magnesium alloy melt purification method, and a magnesium alloy component manufacturing method. Background Technology

[0002] Low-aluminum magnesium alloys (Al≤6.5%) have become the dominant material for semi-solid injection molding processes due to their good fluidity, lightweight potential, and moderate cost. Among common grades, AZ31B magnesium alloy has the best plasticity and excellent corrosion resistance, and is mainly used in automotive body panels and 3C product shells; AZ40 magnesium alloy has higher strength than AZ31B magnesium alloy and is mainly used in structural components; AM60B magnesium alloy has excellent casting performance and high ductility, and is mainly used in automotive wheels and steering wheels; AS31B magnesium alloy has good heat resistance and strong creep resistance, and is mainly used in engine parts.

[0003] However, despite their individual advantages, these magnesium alloys exhibit significant differences in melt characteristics: AZ-based magnesium alloys contain Zn, resulting in a dense oxide film, but are prone to forming high-melting-point ZnO inclusions; AM-based magnesium alloys contain Mn, where Al-Mn compounds easily become inclusions; and AS-based magnesium alloys contain Si, which readily forms hard and brittle Mg2Si particles, affecting fluidity. The presence of these inclusions or hard particles poses a serious challenge to melt purity and the uniformity of semi-solid slurry.

[0004] While traditional RJ-2 flux is widely used in magnesium alloy casting, it is difficult to simultaneously adapt to the diverse melt characteristics mentioned above, and its practical application in semi-solid injection molding processes presents the following problems:

[0005] 1. Poor temperature adaptability: RJ-2 flux is designed for liquid casting of magnesium alloys (700~750℃), and its active components can only react fully at high temperatures; however, in the process range of semi-solid injection molding (560~620℃), the activity of the flux will decrease significantly, and it will be unable to effectively wet, adsorb or remove inclusions, resulting in poor purification effect.

[0006] 2. Rapid decomposition and insufficient action time: Under the purification temperature of existing semi-solid injection molding processes, the effective action time of RJ-2 flux is only 3-5 minutes. However, semi-solid injection molding often requires a long melt holding and homogenization process. Premature flux failure means that subsequently generated inclusions cannot be removed in time, resulting in an incomplete purification process and affecting the mechanical properties of the final product.

[0007] 3. High risk of inclusions: The density of RJ-2 flux is similar to that of magnesium alloy melt, making it difficult to achieve good separation through density difference during stirring or settling. Residual flux or reaction products are easily drawn into the slurry, forming inclusion defects and reducing the density and yield of the finished product.

[0008] 4. Environmental and safety issues: Traditional refining processes often use highly toxic degassing agents such as hexachloroethane (C2Cl6), which decompose at high temperatures to produce highly toxic gases such as chlorine and hydrogen chloride. This not only seriously endangers the health of operators but also causes environmental pollution, failing to meet the requirements of green manufacturing.

[0009] In summary, the traditional RJ-2 flux cannot meet the special requirements of semi-solid injection molding of low-aluminum magnesium alloys in terms of component compatibility, temperature window, action time, separation ability and environmental performance. There is an urgent need to develop a new type of purification agent that is compatible with the semi-solid injection molding process of low-aluminum magnesium alloys and is efficient and universal. Summary of the Invention

[0010] To address the shortcomings of the existing technologies, this invention provides a high-efficiency purifying agent for low-aluminum semi-solid injection molding of magnesium alloys, its preparation method, a magnesium alloy melt purification method, and a magnesium alloy component manufacturing method. This solves the problems of existing purifying agents being unable to adapt to the differences in melt composition and other practical applications in the semi-solid injection molding process of low-aluminum magnesium alloys. At the same time, it provides a novel purifying agent that is compatible with the semi-solid injection molding process of low-aluminum magnesium alloys, and is highly efficient and universally applicable.

[0011] The first aspect of this invention provides a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys, wherein the raw material components are composed of the following mass percentages: 60-69 wt.% core purifying component, 23-28 wt.% auxiliary purifying component, and 8-12 wt.% microcapsule coating component. The core purifying component includes anhydrous magnesium chloride MgCl2, anhydrous potassium chloride KCl, anhydrous calcium chloride CaCl2, and rare earth chloride RECl3. The auxiliary purifying component includes calcium fluoride CaF2, sodium carbonate Na2CO3, sodium bicarbonate NaHCO3, and cryolite Na3AlF6. The microcapsule coating component includes nano-magnesium oxide MgO and polylactic acid-glycolic acid copolymer PLGA.

[0012] Preferably, the magnesium alloy is an AZ-based, AM-based, or AS-based magnesium alloy with an Al content of 2.0–6.5 wt.%.

[0013] In the core purification components, anhydrous magnesium chloride (MgCl2) is 28–30 wt.%, anhydrous potassium chloride (KCl) is 16–18 wt.%, anhydrous calcium chloride (CaCl2) is 10–14 wt.%, and rare earth chloride (RECl3) is 6–8 wt.%, of which rare earth chloride (RECl3) is one or more of lanthanum chloride (LaCl3) and cerium chloride (CeCl3).

[0014] In the auxiliary purification components, calcium fluoride (CaF2) accounts for 12–14 wt.%, sodium carbonate (Na2CO3) accounts for 6–7 wt.%, sodium bicarbonate (NaHCO3) accounts for 3–4 wt.%, and cryolite (Na3AlF6) accounts for 2–3 wt.%.

[0015] In the microcapsule coating components, nano-magnesium oxide (MgO) accounts for 5–7 wt.% and polylactic acid-glycolic acid copolymer (PLGA) accounts for 3–5 wt.%.

[0016] Preferably, the rare earth chloride RECl3 is a mixture of lanthanum chloride LaCl3 and cerium chloride CeCl3, wherein the mass ratio of lanthanum chloride LaCl3 to cerium chloride CeCl3 is 1.5 to 2.5:1;

[0017] The particle size of nano-magnesium oxide (MgO) is 50–200 nm, and the purity is ≥99.9%; the molecular weight of polylactic acid-glycolic acid copolymer (PLGA) is 50,000–100,000, and the molar ratio of lactic acid to glycolic acid is 75:25.

[0018] Preferably, the mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) is 2:1.

[0019] The second aspect of this invention provides a method for preparing a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys, comprising the following steps:

[0020] S11, Raw material pretreatment;

[0021] S12, Microcapsule Coating: Based on the pretreated core purification components and microcapsule coating components, an inner and outer phase suspension was prepared, and then core-shell structured microcapsule particles were prepared using coaxial electrospray technology.

[0022] S13, Ultrasonic-assisted granulation: The obtained core-shell structured microcapsule particles are mixed with auxiliary purification components, subjected to continuous power ultrasonic treatment, and then pressed into shape to obtain the initial purification agent.

[0023] S14. Surface activation treatment: At 150-180℃, 1-2 vol% SF6 / CO2 mixed gas is introduced to activate the initial purifying agent to obtain the purifying agent. The activation treatment time is 30-60 min.

[0024] Preferably, step S11 specifically includes:

[0025] S111. Anhydrous magnesium chloride (MgCl2) was vacuum dried at 320±10℃ for 5.0±0.5h, with a vacuum degree <-0.095MPa, and the moisture content after vacuum drying was <0.03%.

[0026] S112. Anhydrous potassium chloride (KCl) was vacuum dried at 300±10℃ for 4.0±0.5h, with a vacuum degree <-0.095MPa, and the moisture content after vacuum drying was <0.02%.

[0027] S113. Anhydrous calcium chloride (CaCl2) was vacuum dried at 350±10℃ for 6.0±0.5h, with a vacuum degree <-0.095MPa, and the moisture content after vacuum drying was <0.05%.

[0028] S114. The rare earth chloride RECl3 was vacuum dried at 250±10℃ for 4.0±0.5h, with a vacuum degree of <-0.090MPa. After the vacuum drying process, it was ground. The moisture content after vacuum drying was <0.10%, and the particle size of the ground rare earth chloride RECl3 was <100μm.

[0029] S115. Calcium fluoride (CaF2) is dried at 120±5℃ under normal pressure for 2.0±0.5h. The moisture content after drying is <0.10%.

[0030] S116. Sodium carbonate (Na2CO3) was dried at 110±5℃ under normal pressure for 2.0±0.5h, and the moisture content after drying was <0.15%.

[0031] S117. Cryolite Na3AlF6 was dried at 135±5℃ under normal pressure for 2.0±0.5h, and the moisture content after drying was <0.10%;

[0032] S118. Nano-sized magnesium oxide (MgO) is vacuum dried at 120±5℃ for 2.0±0.5h, with a vacuum degree <-0.090MPa, and the moisture content after drying is <0.10%.

[0033] S119. Polylactic acid-glycolic acid copolymer (PLGA) was vacuum dried at 40±2℃ for 12 hours, with a vacuum degree < -0.090MPa, and the moisture content after drying was <0.05%.

[0034] Step S12 is as follows:

[0035] S121. Preparation of internal phase suspension: The pretreated core purification component is mixed with nano-magnesium oxide (MgO) to obtain a first mixed powder. The first mixed powder is then added to anhydrous ethanol and ultrasonically dispersed at a frequency of 40 kHz for 30 min to obtain an internal phase suspension. The solid-liquid mass ratio of the first mixed powder to anhydrous ethanol is 1 g: 2.5-3.5 mL.

[0036] S122. Preparation of external phase suspension: The pretreated polylactic acid-glycolic acid copolymer (PLGA) was dissolved in dichloromethane (CH2Cl2) and magnetically stirred at 600 rpm for 4 hours to obtain an external phase suspension, wherein the concentration of PLGA in the external phase suspension was 8–12 wt.%.

[0037] S123. Set the coaxial electrospray process parameters: the flow rate of the inner phase suspension is 0.8±0.05mL / h, the flow rate of the outer phase suspension is 2.0±0.1mL / h, the working voltage is 18±0.5kV, the receiving distance is 18±1cm, the inner diameter of the inner nozzle is 0.4mm, and the inner diameter of the outer nozzle is 1.2mm.

[0038] S124. Three-stage temperature control for preparing core-shell structured microcapsule particles: A coaxial electrospray device is used to simultaneously draw in the inner phase suspension and the outer phase suspension. Then, a three-stage temperature control setting is activated for coaxial electrospray to obtain core-shell structured microcapsule particles. The inner nozzle delivers the inner phase suspension, and the outer nozzle delivers the outer phase suspension. The coaxial electrospray device consists of a nozzle section, a flight section, and a receiving section. The three-stage temperature control setting is as follows: the nozzle section temperature is 45±2℃, the flight section temperature is 25±3℃, and the receiving section temperature is 8±2℃.

[0039] S125. Post-processing: The obtained core-shell structured microcapsule particles were vacuum dried at 40±2℃ for 12h, with a vacuum degree of <-0.090MPa.

[0040] Step S13 is as follows:

[0041] S131. Mixing treatment: The obtained core-shell structured microcapsule particles, sodium bicarbonate NaHCO3, and pretreated calcium fluoride CaF2, sodium carbonate Na2CO3 and cryolite Na3AlF6 are mixed to obtain a second mixed powder.

[0042] S132. Continuous Power Ultrasonic Treatment: The second mixed powder is subjected to continuous power ultrasonic treatment, wherein the ultrasonic frequency is 20–40 kHz and the power density is 30–50 W / cm³. 2 The duration of ultrasonic treatment is 10–15 minutes;

[0043] S133, Compression molding: The second mixed powder after continuous power ultrasonic treatment is compressed into a spherical mold to obtain the initial purifying agent. The compression pressure is 150-259 MPa, the holding time is 10-30 s, and the diameter of the spherical mold is 3-5 mm.

[0044] Preferably, after the microcapsule encapsulation process, the residual amount of anhydrous ethanol is <100ppm and the residual amount of dichloromethane (CH2Cl2) is <50ppm.

[0045] The prepared core-shell structured microcapsule particles consist of a core, a porous core adsorption layer, and a PLGA controlled-release outer shell layer coating the porous core adsorption layer. The core is formed by the core purification component; the porous core adsorption layer is a porous layer of MgO nano-oxide formed by the electrostatic self-assembly of MgO nano-oxide onto the core surface, with a thickness of 10–15 μm and a specific surface area >80 m². 2 / g; The PLGA controlled-release outer shell is formed by coating the porous adsorption core layer with polylactic acid-glycolic acid copolymer PLGA through a phase separation method, and the thickness is 20-30μm.

[0046] The obtained core-shell structured microcapsule particles have a microcapsule yield of >85%, an encapsulation rate of >95%, and a D50 particle size of 120±20μm.

[0047] The initial purifying agent consists of multiple particles with a uniform spherical appearance; each spherical purifying agent particle has a particle size of 3-5 mm, a porosity of 20±3%, and a compressive strength ≥5 MPa;

[0048] The total effective action time of the prepared purifying agent is 13-18 minutes.

[0049] A third aspect of this invention provides a method for purifying magnesium alloy melt, which uses a purifying agent prepared by a method for preparing a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloy to purify the magnesium alloy melt, comprising the following steps:

[0050] S21. Solid magnesium alloy is melted at 700℃ under a 0.5 vol% SF6 / CO2 mixed atmosphere. After complete melting, the solid magnesium alloy is held at this temperature for 10–15 minutes. Then, the magnesium alloy melt is cooled to a semi-solid range of 560–620℃ at a cooling rate of 5℃ / min, so that the solid fraction of the magnesium alloy melt reaches 30–50%. A purifying agent is then added to the magnesium alloy melt, wherein the purifying agent accounts for 0.3–0.8 wt.% of the mass of the magnesium alloy melt.

[0051] S22. The magnesium alloy melt with added purifying agent is mechanically stirred, followed by pulsed power ultrasonic treatment. During mechanical stirring, the rotation speed is 200–400 rpm, and the stirring time is 5–10 min. During pulsed power ultrasonic treatment, the ultrasonic frequency is 20–40 kHz, and the power density is 30 W / cm³. 2 The ultrasonic treatment time is 10-15 minutes, and the ultrasonic working mode is intermittent with a duty cycle of 1:1.

[0052] S23. After the pulsed power ultrasonic treatment is completed, let it stand for 3-5 minutes, then remove the slag and stop the introduction of the 0.5 vol% SF6 / CO2 mixed atmosphere to obtain the purified magnesium alloy melt.

[0053] The fourth aspect of this invention provides a method for manufacturing magnesium alloy components. The method involves injection molding a magnesium alloy melt treated by a magnesium alloy melt purification method to obtain the magnesium alloy component. Specifically, the purified magnesium alloy melt is water-cooled or mist-cooled to 550-580°C at a cooling rate of 10-20°C / min under a 0.5 vol% SF6 / CO2 mixed atmosphere to obtain a semi-solid slurry. The 0.5 vol% SF6 / CO2 mixed atmosphere is then stopped, and the semi-solid slurry is used to prepare the magnesium alloy component using an injection molding process.

[0054] Preferably, the 0.5 vol% SF6 / CO2 mixed atmosphere is continuously introduced from the magnesium alloy melt purification step and without interruption between the magnesium alloy melt purification step and the magnesium alloy component manufacturing step, until the semi-solid slurry is obtained and then the mixed atmosphere is stopped.

[0055] The obtained magnesium alloy components have an inclusion removal rate of ≥88.0% and a hydrogen content of ≤9 cm⁻¹. 3 / 100g, tensile strength ≥278MPa, yield strength ≥175MPa, elongation ≥14.5%, corrosion rate ≤0.32mm / y, flux residue ≤0.040%.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] 1. The purifying agent prepared in this invention exhibits a complex synergistic mechanism among its components. The basic salt system, composed of anhydrous magnesium chloride (MgCl2), anhydrous potassium chloride (KCl), and anhydrous calcium chloride (CaCl2), provides a low-melting-point and highly fluid carrier environment. In this environment, rare earth chloride (RECl3) can exert a deep chemical purification effect. Leveraging its strong chemical affinity and high reactivity for various oxide inclusions (MgO, Al2O3, ZnO, Al-Mn, Mg2Si, etc.), it achieves directional purification of these inclusions. Adsorption and deep removal: Calcium fluoride (CaF2) and cryolite (Na3AlF6) can adjust the physical properties of magnesium alloy melt, reducing viscosity and improving wettability; sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) constitute a composite foaming system to achieve gentle yet deep degassing, completely replacing toxic hexachloroethane (C2Cl6); nano-magnesium oxide (MgO) provides an active capture mechanism for physical adsorption; polylactic acid-glycolic acid copolymer (PLGA) serves as an intelligent controlled-release carrier, ensuring that each component is released within the optimal temperature and time period to maximize purification efficiency.

[0058] 2. This invention employs a rare earth-alkaline earth metal chloride-fluoride composite molten salt system and coaxial electrospray microcapsule encapsulation technology to design a purifying agent specifically for the semi-solid region. This not only avoids the problem of re-oxidation caused by cooling after liquid purification, but also achieves in-situ purification in the semi-solid region (560-620℃) for the first time. At the same time, it couples the two independent processes of melt purification and semi-solid molding into an integrated in-situ treatment, which not only reduces one heating-cooling cycle, thus reducing energy consumption by about 30%, but also effectively shortens the production cycle and improves production efficiency.

[0059] 3. The multi-mechanism synergistic purification system provided by this invention can adapt to the purification needs of different types of low-aluminum magnesium alloys such as AZ series, AM series and AS series, and has broad applicability and excellent purification effect.

[0060] 4. The purifier provided by this invention has a shelf life of >18 months and a moisture absorption rate of <0.05% due to the protection of the PLGA controlled-release shell layer, and exhibits excellent stability.

[0061] 5. In the magnesium alloy melt purification process provided by this invention, the amount of purifying agent used is less than that of commercial RJ-2 flux, resulting in a significant cost advantage; at the same time, the preparation process is standardized, and all parameters are precisely controllable, making it suitable for large-scale industrial production. Attached Figure Description

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 This is a macroscopic morphology diagram of the purifying agent prepared in Example 1 of the present invention; Figure 2 SEM morphology of inclusions in magnesium alloy sheet components obtained directly using the preparation process of Example 1 without using a purification agent to clean the magnesium alloy melt, with a magnification of 200x; Figure 3 SEM morphology of inclusions in magnesium alloy sheet components obtained directly using the preparation process of Example 1 without using a purifying agent to purify the magnesium alloy melt, with a magnification of 300x; Figure 4 SEM morphology of inclusions in magnesium alloy sheet components obtained directly using the preparation process of Example 1 without using a purification agent to clean the magnesium alloy melt, with a magnification of 500x; Figure 5 SEM morphology of inclusions in magnesium alloy sheet components obtained directly using the preparation process of Example 1 without using a purification agent to clean the magnesium alloy melt, with a magnification of 1000x; Figure 6 The image shows the SEM morphology of inclusions in a magnesium alloy sheet component prepared using the purifying agent obtained in Example 1 after purifying the magnesium alloy melt, with a magnification of 200x. Figure 7 The image shows the SEM morphology of inclusions in a magnesium alloy sheet component prepared using the purifying agent obtained in Example 1 after purifying the magnesium alloy melt, with a magnification of 300x. Figure 8 The image shows the SEM morphology of inclusions in a magnesium alloy sheet component prepared using the purifying agent obtained in Example 1 after purifying the magnesium alloy melt, with a magnification of 500x. Figure 9 The image shows the SEM morphology of inclusions in a magnesium alloy sheet component prepared using the purifying agent obtained in Example 1 and then processed using the preparation process of Example 1. The magnification is 1000x. Detailed Implementation

[0064] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] The first aspect of the present invention provides a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys, wherein the raw material components are composed of the following mass percentages: core purifying component 60-69 wt.%, auxiliary purifying component 23-28 wt.%, and microcapsule coating component 8-12 wt.%.

[0066] In this application, the magnesium alloy is an AZ-based, AM-based, or AS-based magnesium alloy with an Al content of 2.0 to 6.5 wt.%. The AZ-based magnesium alloy includes AZ31B, AZ40, and AZ61A magnesium alloys; the AM-based magnesium alloy includes AM60B and AM50A magnesium alloys; and the AS-based magnesium alloy includes AS31B and AS41B magnesium alloys.

[0067] In the embodiments of this application, the Al content in AZ31B magnesium alloy is 2.5-3.5 wt.% and the Zn content is 0.6-1.4 wt.%, the Al content in AZ40 magnesium alloy is 3.0-4.0 wt.% and the Zn content is 0.8-1.5 wt.%, and the Al content in AZ61A magnesium alloy is 5.5-6.5 wt.% and the Zn content is 0.5-1.5 wt.%.

[0068] In the embodiments of this application, the Al content in AM60B magnesium alloy is 5.5-6.5 wt.% and the Mn content is 0.25-0.6 wt.%, while the Al content in AM50A magnesium alloy is 4.4-5.4 wt.% and the Mn content is 0.25-0.6 wt.%.

[0069] In the embodiments of this application, the Al content in AS31B magnesium alloy is 2.5-3.5 wt.% and the Si content is 0.6-1.4 wt.%, and the Al content in AS41B magnesium alloy is 3.5-4.5 wt.% and the Si content is 0.6-1.4 wt.%.

[0070] In this application, the core purification components include anhydrous magnesium chloride MgCl2 28-30 wt.%, anhydrous potassium chloride KCl 16-18 wt.%, anhydrous calcium chloride CaCl2 10-14 wt.%, and rare earth chloride RECl3 6-8 wt.%.

[0071] In this application, anhydrous magnesium chloride (MgCl2) is the main base of the purifying agent. Anhydrous magnesium chloride (MgCl2) and anhydrous potassium chloride (KCl) form a low-melting-point eutectic system with a eutectic temperature of approximately 450°C. This characteristic ensures that the purifying agent maintains good liquid fluidity within the semi-solid range (560–620°C) of low-alumina magnesium alloys. Furthermore, anhydrous magnesium chloride (MgCl2) can react with magnesium oxide inclusions in the magnesium alloy melt to form a complex of magnesium chloride and magnesium oxide, thereby dissolving and removing the magnesium oxide inclusions.

[0072] In this application, anhydrous potassium chloride (KCl) is mainly used to form a eutectic system with anhydrous magnesium chloride (MgCl2), lowering the overall melting point and improving the fluidity of the purifying agent. More importantly, anhydrous potassium chloride (KCl) can disrupt the surface film structure of magnesium oxide, making dense magnesium oxide particles loose and promoting the aggregation and flotation separation of inclusions. Furthermore, the presence of anhydrous potassium chloride (KCl) can also regulate the density of the purifying agent, maintaining an appropriate density difference with the magnesium alloy melt, which is beneficial for separation after purification.

[0073] In this application, anhydrous calcium chloride (CaCl2) is a highly hygroscopic substance capable of deeply removing moisture from magnesium alloy melts, preventing an increase in hydrogen content due to residual moisture. Simultaneously, calcium ions have a strong affinity for aluminum, exhibiting preferential reaction and removal capabilities for alumina inclusions commonly found in low-alumina magnesium alloys. Furthermore, anhydrous calcium chloride (CaCl2) can significantly reduce the viscosity of magnesium alloy melts, promoting the flotation and separation of inclusions within the melt and improving purification efficiency.

[0074] Preferably, the rare earth chloride RECl3 is one or more of lanthanum chloride LaCl3 and cerium chloride CeCl3.

[0075] In this application, the rare earth chloride RECl3 is a mixture of lanthanum chloride LaCl3 and cerium chloride CeCl3, wherein the mass ratio of lanthanum chloride LaCl3 to cerium chloride CeCl3 is 1.5 to 2.5:1.

[0076] In the embodiments of this application, the preferred mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) is 2:1.

[0077] In this application, rare earth chloride RECl3 is the core innovative component of the purifying agent provided by this invention. RECl3 is a mixture of lanthanum chloride (LaCl3) and cerium chloride (CeCl3). Lanthanum and cerium ions have extremely strong chemical reactivity and a strong affinity for elements such as oxygen, sulfur, and hydrogen, enabling the formation of stable rare earth oxides and rare earth sulfides, thereby deeply removing oxide and sulfide inclusions and gases from the magnesium alloy melt. Furthermore, rare earth elements can significantly reduce the surface tension of the magnesium alloy melt, promoting the aggregation and flotation of inclusions on the surface of the magnesium alloy melt.

[0078] It should be noted that when lanthanum chloride (LaCl3) and cerium chloride (CeCl3) are prepared at a mass ratio of 1.5–2.5:1, the reaction kinetics between the purifying agent and different low-alumina magnesium alloy melts can be optimized, avoiding the problem of excessively vigorous or insufficient reaction of a single rare earth element, thereby effectively improving the removal efficiency of oxide inclusions. Compared with purifying agents using a single rare earth element, this application improves the purification efficiency of the purifying agent by 15–25% by using the rare earth chloride RECl3. Furthermore, when the mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) is 1.5–2.5:1, the purification efficiency can be maintained at a high level (inclusion removal rate ≥88%), with the optimal purification efficiency achieved at a mass ratio of 2:1. However, when the mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) is <1.5:1 (cerium excess) or >2.5:1 (lanthanum excess), the purification selectivity decreases significantly, and the inclusion removal rate decreases by 3–5%.

[0079] In this application, the auxiliary purification components include calcium fluoride CaF2 12-14 wt.%, sodium carbonate Na2CO3 6-7 wt.%, sodium bicarbonate NaHCO3 3-4 wt.%, and cryolite Na3AlF6 2-3 wt.%.

[0080] In this application, the main mechanism of action of calcium fluoride (CaF2) lies in the fact that fluoride ions can chemically react with silicate inclusions in the magnesium alloy melt to generate volatile silicon tetrafluoride gas, thereby effectively removing silicide inclusions. This effect is particularly important for silicon-containing AS-based magnesium alloys. Furthermore, calcium fluoride (CaF2) can also reduce the viscosity of the magnesium alloy melt, and synergistically with anhydrous calcium chloride (CaCl2) to further promote the separation and flotation of inclusions.

[0081] In this application, sodium bicarbonate (NaHCO3) and sodium carbonate (Na2CO3) constitute a composite foaming system. Sodium bicarbonate (NaHCO3) begins to decompose at 200–300°C, producing CO2 and water vapor, which complements the decomposition temperature of sodium carbonate (Na2CO3), achieving continuous foaming over a wide temperature range and enhancing degassing. Simultaneously, the water vapor produced by the decomposition of sodium bicarbonate (NaHCO3) reacts with magnesium at high temperatures to generate oxide inclusions and H2. As the H2 bubbles rise, they adsorb and carry the inclusions to the surface of the magnesium alloy melt, thus achieving a synergistic effect of physical and chemical degassing, significantly improving the purification effect. Furthermore, the composite foaming system composed of sodium bicarbonate (NaHCO3) and sodium carbonate (Na2CO3) can completely replace the obsolete hexachloroethane (C2Cl6), achieving environmentally friendly degassing and meeting green manufacturing requirements.

[0082] In this application, cryolite Na3AlF6 is mainly used to further reduce the melting point of the purifying agent system, improve the wettability of the purifying agent with the magnesium alloy melt, and ensure that the purifying agent can fully contact and react with the magnesium alloy melt, thereby improving the uniformity and thoroughness of the purification.

[0083] In this application, the microcapsule coating components include 5-7 wt.% nano-magnesium oxide (MgO) and 3-5 wt.% polylactic acid-glycolic acid copolymer (PLGA).

[0084] In this application, nano-magnesium oxide (MgO) is tightly adsorbed onto the surface of the core purification component through electrostatic self-assembly, forming a layer with a thickness of 10–15 μm and a specific surface area >80 m². 2 The core porous adsorption layer has a density of / g. This adsorption layer has extremely strong physical adsorption capacity, which can actively capture oxide inclusions in magnesium alloy melt, significantly improving the purification efficiency by about 30%. In addition, nano-magnesium oxide (MgO) can also serve as a heterogeneous nucleation substrate to refine the microstructure of the purifier particles.

[0085] In this application, polylactic acid-glycolic acid copolymer (PLGA) is used to form a controlled-release shell layer of PLGA with a thickness of 20–30 μm. The glass transition temperature of PLGA is 55–60 °C, and its melting point is 165–175 °C. This temperature characteristic is an inherent physical property of the material, determined by the molar ratio of lactic acid to glycolic acid (75:25) and its molecular weight (50,000–100,000). Simultaneously, this temperature characteristic (when the glass transition temperature exceeds the semi-solid range, sustained release cannot be initiated; when the glass transition temperature is too low, it is prone to adhesion during room temperature storage, leading to a shortened shelf life) ensures that it undergoes gradual degradation within the semi-solid range (560–620 °C) of low-aluminum magnesium alloys, thereby achieving a three-stage stepped sustained release of the purifier. The first stage occurs at 560–580 °C, at which point the PLGA begins to soften, releasing 5%–10% of the total auxiliary purifier components (mainly sodium carbonate Na₂CO₃ and a small amount of other components). The first stage involves pre-purification with sodium bicarbonate (NaHCO3) to reduce the viscosity of the magnesium alloy melt, lasting 2–3 minutes. The second stage occurs at 580–600°C, where polylactic acid-glycolic acid copolymer (PLGA) gradually degrades, releasing 60%–75% of the total core purification components (anhydrous magnesium chloride (MgCl2), anhydrous potassium chloride (KCl), anhydrous calcium chloride (CaCl2), and rare earth chlorides (RECl3)) and cryolite (Na3AlF6) for the main purification reaction, deeply removing various inclusions, lasting 8–10 minutes. The third stage occurs at 600–620°C, where PLGA rapidly decomposes, releasing the remaining auxiliary purification components (including calcium fluoride (CaF2) and sodium bicarbonate (NaHCO3)) and the core purification components, completing deep degassing and final purification, lasting 3–5 minutes. Therefore, the purification agent provided in this application has a total effective action time of 13–18 minutes, which is 3–5 times longer than the total effective action time (3–5 minutes) of traditional purification agents. This significant time advantage is the core mechanism by which the purifier provided by this invention achieves high-efficiency purification—through the precise design of the PLGA controlled-release shell layer, the effective release window of the purifier is extended from 3-5 minutes to 13-18 minutes, thereby doubling the purification efficiency under the same dosage conditions.

[0086] It should be noted that the three-stage stepped slow release is the passive degradation behavior of polylactic acid-glycolic acid copolymer (PLGA) in the semi-solid range (560-620℃), which is determined by the glass transition temperature and melting point of PLGA itself. At the same time, the duration of each stage is the result of the coupling between the characteristics of PLGA material and temperature, and is not artificially set.

[0087] It is important to note that the porous adsorption layer in the core primarily captures impurities through physical adsorption (van der Waals forces, electrostatic interactions), rather than through chemical reactions that release active ions for purification. Its high specific surface area (>80m²) contributes to this purification process. 2 The MgO nanoparticles (MgO) can exert their adsorption effect in the initial stage of contact with the melt, without waiting for release within a specific temperature range. In this application, the MgO nanoparticles are located in the porous adsorption layer of the core, and are coated by the PLGA controlled-release shell layer together with the core purification component. During the gradual degradation of the polylactic acid-glycolic acid copolymer (PLGA), the MgO nanoparticles are exposed to the melt along with the release of the core purification component, or remain in the microcapsule framework to continue to exert their physical adsorption effect, forming a synergistic effect with the chemical purification of the core purification component.

[0088] Preferably, the nano-magnesium oxide (MgO) has a particle size of 50–200 nm and a purity of ≥99.9%; the polylactic acid-glycolic acid copolymer (PLGA) has a molecular weight of 50,000–100,000 and a molar ratio of lactic acid to glycolic acid of 75:25.

[0089] It should be noted that 50–200 nm is the optimal particle size range for electrostatic self-assembly to form a porous adsorption layer with a core. When the particle size of nano-magnesium oxide (MgO) is 50–200 nm, its theoretical specific surface area is 30–50 m². 2 / g, after being tightly adsorbed onto the surface of the core purification component through electrostatic self-assembly, can form a layer with a thickness of 10-15μm and a specific surface area >80m². 2 The core porous adsorption layer has a density of / g. This adsorption layer has extremely strong physical adsorption capacity and can actively capture oxide inclusions in magnesium alloy melt, improving the purification efficiency by about 30%. If the particle size of nano-magnesium oxide (MgO) is <50nm, the particles are prone to agglomeration, resulting in significant resistance during the dispersion process, making it difficult to achieve uniform distribution through electrostatic self-assembly, and the core porous adsorption layer cannot reach a dense state; if the particle size of nano-magnesium oxide (MgO) is >200nm, the specific surface area of ​​the particles will be significantly reduced (below 50nm). 2 / g), its active adsorption capacity weakens accordingly, which in turn reduces the removal rate of impurities by about 9 percentage points.

[0090] It should be noted that a molecular weight of 50,000 to 100,000 ensures that polylactic acid-glycolic acid copolymer (PLGA) achieves a three-stage, stepwise slow release in the semi-solid range (560–620°C). Within this molecular weight range, the degradation rate of PLGA ensures that the purifier is released in stages within 13–18 minutes, covering the main action period of the semi-solid purification process and meeting the requirements for slow-release characteristics in the semi-solid purification process. If the molecular weight of PLGA is <50,000, the shell mechanical strength is insufficient, and premature rupture is likely to occur, resulting in poor slow-release effect; if the molecular weight of PLGA is >100,000, the material degradation rate is too slow, and it is very likely that complete release cannot be achieved even at 620°C, ultimately causing incomplete purification.

[0091] The second aspect of this invention provides a method for preparing a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys, comprising the following steps:

[0092] S11. Raw material pretreatment.

[0093] It should be noted that the sodium bicarbonate (NaHCO3) in this application does not require atmospheric pressure drying; it is sealed and stored in a desiccator and can be removed from the desiccator when needed. Therefore, all raw materials except NaHCO3 in this application undergo pretreatment.

[0094] In this application, step S11 specifically includes:

[0095] S111. Anhydrous magnesium chloride (MgCl2) was vacuum dried at 320±10℃ for 5.0±0.5h, with a vacuum degree of <-0.095MPa, and the moisture content after vacuum drying was <0.03%.

[0096] In this application, the water of crystallization can be removed by vacuum drying of anhydrous magnesium chloride (MgCl2), thus preventing hydrogen enrichment in the melt.

[0097] S112. Anhydrous potassium chloride (KCl) was vacuum dried at 300±10℃ for 4.0±0.5h, with a vacuum degree of <-0.095MPa. The moisture content after vacuum drying was <0.02%.

[0098] In this application, vacuum drying of anhydrous potassium chloride (KCl) ensures the formation of a low-melting-point eutectic.

[0099] S113. Anhydrous calcium chloride (CaCl2) was vacuum dried at 350±10℃ for 6.0±0.5h, with a vacuum degree of <-0.095MPa, and the moisture content after vacuum drying was <0.05%.

[0100] It should be noted that anhydrous calcium chloride (CaCl2) is a highly absorbent raw material. In this application, by performing vacuum drying, the anhydrous calcium chloride (CaCl2) can be deeply dehydrated, significantly reducing the moisture content in the raw material and meeting the strict requirements for the degree of dryness of the raw material during subsequent production and processing.

[0101] S114. The rare earth chloride RECl3 is vacuum dried at 250±10℃ for 4.0±0.5h, with a vacuum degree of <-0.090MPa. After vacuum drying, it is ground. The moisture content after vacuum drying is <0.10%, and the particle size of the ground rare earth chloride RECl3 is <100μm.

[0102] It should be noted that rare earth chloride RECl3 is prone to hydrolysis. In this application, vacuum drying is used to effectively prevent the hydrolysis reaction from occurring.

[0103] S115. Calcium fluoride (CaF2) is dried at 120±5℃ under normal pressure for 2.0±0.5h. The moisture content after drying is <0.10%.

[0104] S116. Sodium carbonate (Na2CO3) is dried at 110±5℃ under normal pressure for 2.0±0.5h. The moisture content after drying is <0.15%.

[0105] S117. Dry cryolite Na3AlF6 at 135±5℃ under normal pressure for 2.0±0.5h. The moisture content after drying is <0.10%.

[0106] In this application, by drying calcium fluoride (CaF2) under normal pressure, adsorbed water on the surface of calcium fluoride (CaF2) can be removed; by drying sodium carbonate (Na2CO3) under normal pressure, decomposition of sodium carbonate (Na2CO3) at high temperature can be prevented; and by drying cryolite (Na3AlF6) under normal pressure, the crystal lattice structure of cryolite (Na3AlF6) can be stabilized.

[0107] S118. Nano-magnesium oxide (MgO) is vacuum dried at 120±5℃ for 2.0±0.5h, with a vacuum degree of <-0.090MPa, and the moisture content after drying is <0.10%.

[0108] S119. The polylactic acid-glycolic acid copolymer (PLGA) was vacuum dried at 40±2℃ for 12h, with a vacuum degree of <-0.090MPa, and the moisture content after drying was <0.05%.

[0109] In this application, anhydrous magnesium chloride (MgCl2), anhydrous potassium chloride (KCl), anhydrous calcium chloride (CaCl2), calcium fluoride (CaF2), sodium carbonate (Na2CO3), cryolite (Na3AlF6), nano-magnesium oxide (MgO), and polylactic acid-glycolic acid copolymer (PLGA) are pretreated in a drying room with a dew point < -40°C; rare earth chloride (RECl3) is pretreated in an argon glove box (water and oxygen < 1 ppm).

[0110] It should be noted that rare earth chloride RECl3 is highly susceptible to hydrolysis. When it comes into contact with moisture in the air, it will generate RE(OH)3 and HCl. Therefore, it needs to be pretreated in an argon glove box (water and oxygen <1ppm).

[0111] S12, Microcapsule Coating: Based on the pretreated core purification components and microcapsule coating components, an inner and outer phase suspension is prepared, and then core-shell structured microcapsule particles are prepared using coaxial electrospray technology.

[0112] In this application, step S12 specifically includes:

[0113] S121. Preparation of internal phase suspension: The pretreated core purification component is mixed with nano-magnesium oxide (MgO) to obtain a first mixed powder. The first mixed powder is then added to anhydrous ethanol and ultrasonically dispersed at a frequency of 40 kHz for 30 min to obtain an internal phase suspension. The solid-liquid mass ratio of the first mixed powder to anhydrous ethanol is 1 g: 2.5-3.5 mL.

[0114] In this embodiment of the application, the mass ratio of the pretreated core purification component to nano-magnesium oxide (MgO) in the first mixed powder is preferably 8-12:1.

[0115] It should be noted that the surface of nano-magnesium oxide (MgO) carries a positive charge (Zeta potential > +30mV), while the core purification component (chloride) carries a negative charge in anhydrous ethanol. Ultrasonic dispersion treatment can promote electrostatic attraction, causing nano-magnesium oxide (MgO) to spontaneously adsorb onto the surface of the core purification component, forming a porous core adsorption layer. Therefore, in this application, the porous core adsorption layer is formed by utilizing the self-assembly characteristics of the material surface charge difference, without the need to apply an additional electric field.

[0116] S122. Preparation of external phase suspension: Dissolve the pretreated polylactic acid-glycolic acid copolymer (PLGA) in dichloromethane (CH2Cl2) and stir magnetically at 600 rpm for 4 hours to obtain an external phase suspension, wherein the concentration of polylactic acid-glycolic acid copolymer (PLGA) in the external phase suspension is 8-12 wt.%.

[0117] S123. Set the coaxial electrospray process parameters: the flow rate of the inner phase suspension is 0.8±0.05mL / h, the flow rate of the outer phase suspension is 2.0±0.1mL / h, the working voltage is 18±0.5kV, the receiving distance is 18±1cm, the inner diameter of the inner nozzle is 0.4mm, and the inner diameter of the outer nozzle is 1.2mm.

[0118] S124. Three-stage temperature control for preparing core-shell structured microcapsule particles: A coaxial electrospray device is used to simultaneously draw in the inner phase suspension and the outer phase suspension. Then, a three-stage temperature control setting is activated for coaxial electrospray to obtain core-shell structured microcapsule particles. The inner nozzle delivers the inner phase suspension, and the outer nozzle delivers the outer phase suspension. The coaxial electrospray device consists of a nozzle section, a flight section, and a receiving section. The three-stage temperature control setting is as follows: the nozzle section temperature is 45±2℃, the flight section temperature is 25±3℃, and the receiving section temperature is 8±2℃.

[0119] It should be noted that after the three-stage temperature control setting is activated, coaxial electrospraying will only begin after the temperature of each stage reaches the set value and remains stable.

[0120] In this embodiment, the coaxial electrospraying specifically involves: turning on the delivery pumps for the inner and outer phase suspensions, allowing the inner and outer phase suspensions to pass through the inner and outer nozzles at a preset flow rate to form a coaxial liquid flow; under the action of a high-voltage electric field, the coaxial liquid flow breaks down to form droplets with core-shell structures. These droplets undergo solvent evaporation and preliminary shell solidification in the flight stage, and then enter the receiving stage for further solidification, ultimately collecting core-shell structured microcapsule particles on the receiving device.

[0121] In this application, the receiving section is a stainless steel receiving plate perpendicular to the nozzle axis. The distance between the stainless steel receiving plate and the nozzle is 18±1cm. The stainless steel receiving plate is grounded to maintain a stable electric field.

[0122] In this embodiment, the stainless steel receiving plate is made of 316L stainless steel.

[0123] In this embodiment of the application, the receiving section may also be a rotating drum collecting device with its axis parallel to the nozzle axis, so as to realize the continuous and uniform collection of core-shell structured microcapsule particles, wherein the drum rotation speed is 5 to 15 rpm.

[0124] In this application, the shell quality is ensured through a three-stage temperature control system. The nozzle stage temperature is 45±2℃, which reduces the viscosity of the internal and external phase suspensions, maintaining their fluidity and preventing premature solidification. The flight stage temperature is 25±3℃, which promotes the rapid evaporation of the solvents (anhydrous ethanol and dichloromethane CH2Cl2), causing a sudden increase in the local concentration of polylactic acid-glycolic acid copolymer (PLGA), thereby triggering liquid-liquid phase separation. Specifically, the PLGA-rich phase solidifies to form the shell, while the solvent-rich phase evaporates, leaving a microporous structure inside. The receiving stage temperature is 8±2℃, which promotes the rapid vitrification and solidification of the PLGA, forming a dense shell.

[0125] It should be noted that this application employs a three-stage temperature control system, enabling the internal and external phase suspensions to sequentially complete the atomization (nozzle stage), shell formation (flight stage), and solidification (receiving stage) physical processes under different temperature conditions, ultimately producing core-shell structured microcapsule particles. If the entire process is conducted at high temperatures, the solvent will evaporate too quickly, resulting in a loose shell, a rough microcapsule surface, and easy adhesion. Conversely, if the entire process is conducted at low temperatures, the polylactic acid-glycolic acid copolymer (PLGA) will solidify prematurely, failing to form a complete spherical shape and easily clogging the nozzle. Furthermore, without cooling in the receiving stage, the core-shell structured microcapsule particles will remain soft upon landing, easily deforming and clumping together.

[0126] S125. Post-processing: The obtained core-shell structured microcapsule particles were vacuum dried at 40±2℃ for 12h, with a vacuum degree of <-0.090MPa.

[0127] Preferably, after the microcapsule encapsulation process, the residual amount of anhydrous ethanol is <100ppm and the residual amount of dichloromethane (CH2Cl2) is <50ppm.

[0128] Preferably, the obtained core-shell structured microcapsule particles consist of a core, a porous core adsorption layer, and a PLGA controlled-release outer shell layer covering the porous core adsorption layer. The core is formed by the core purification component; the porous core adsorption layer is a porous layer of MgO nano-oxide formed by the electrostatic self-assembly of MgO nano-oxide onto the core surface, with a thickness of 10–15 μm and a specific surface area >80 m². 2 / g; The PLGA controlled-release outer shell is formed by coating the porous adsorption layer of the core with polylactic acid-glycolic acid copolymer PLGA through a phase separation method, and the thickness is 20-30μm.

[0129] It should be noted that the thickness of the core porous adsorption layer refers to the thickness of the nano-magnesium oxide (MgO) porous layer adsorbed on the core surface, i.e., the distance from the surface of the core purification component (i.e., the outer surface of the core) to the outer surface of the nano-magnesium oxide (MgO) porous layer. Furthermore, the specific surface area of ​​the core porous adsorption layer is >80 m².2 / g refers to the specific surface area of ​​the porous structure formed by the electrostatic self-assembly of nano-magnesium oxide (MgO) (measured by the BET method), rather than the theoretical specific surface area of ​​a single nano-magnesium oxide (MgO).

[0130] In this embodiment, the thickness of the porous core adsorption layer is determined by the amount and particle size of nano-magnesium oxide (MgO), while the thickness of the PLGA controlled-release outer shell is determined by the flow rate of the external phase suspension and the concentration of polylactic acid-glycolic acid copolymer (PLGA) in the external phase suspension. If the PLGA controlled-release outer shell is too thin (<20 μm), the slow-release time will be shortened, and the purification efficiency will decrease; if the PLGA controlled-release outer shell is too thick (>30 μm), the degradation will be too slow, and the purifier will not be completely released within the process cycle.

[0131] Preferably, the obtained core-shell structured microcapsule particles have a microcapsule yield >85%, an encapsulation rate >95%, and a D50 particle size of 120±20μm.

[0132] In this embodiment, the microcapsule yield of the core-shell structured microcapsule particles is the ratio of the actual mass of the core-shell structured microcapsule particles obtained to the theoretically expected mass of the core-shell structured microcapsule particles; the encapsulation rate of the core-shell structured microcapsule particles refers to the proportion of core-shell structured microcapsule particles in which the PLGA controlled-release outer shell completely encapsulates the porous adsorption layer of the core core in the actual obtained core-shell structured microcapsule particles, which is an indicator for evaluating the integrity of the encapsulation.

[0133] S13. Ultrasonic-assisted granulation: The obtained core-shell structured microcapsule particles are mixed with auxiliary purification components, subjected to continuous power ultrasonic treatment, and then pressed into shape to obtain the initial purification agent.

[0134] In this application, step S13 specifically includes:

[0135] S131. Mixing treatment: The obtained core-shell structured microcapsule particles, sodium bicarbonate NaHCO3, and pretreated calcium fluoride CaF2, sodium carbonate Na2CO3 and cryolite Na3AlF6 are mixed to obtain a second mixed powder.

[0136] S132. Continuous Power Ultrasonic Treatment: The second mixed powder is subjected to continuous power ultrasonic treatment, wherein the ultrasonic frequency is 20–40 kHz and the power density is 30–50 W / cm³. 2 The duration of ultrasonic treatment is 10–15 minutes;

[0137] S133, Compression molding: The second mixed powder after continuous power ultrasonic treatment is compressed into a spherical mold to obtain the initial purifying agent. The compression pressure is 150-259 MPa, the holding time is 10-30 s, and the diameter of the spherical mold is 3-5 mm.

[0138] In this embodiment, the mass ratio of core-shell structured microcapsule particles to auxiliary purification components in the second mixed powder is preferably 2.5 to 3.5:1.

[0139] In this embodiment of the application, by setting the pressing pressure to 150-259 MPa, it is possible to ensure that a large number of core-shell structured microcapsule particles are bonded into single spherical purifier particles without crushing the hard outer shell of a single core-shell structured microcapsule particle.

[0140] In this application, the initial purifying agent is composed of multiple particles with a uniform spherical appearance; each spherical purifying agent particle has a particle size of 3-5 mm, a porosity of 20±3%, and a compressive strength ≥5 MPa.

[0141] It is important to note that when the particle size of each spherical purifying agent particle is <3mm, it is easily dispersed by the melt flow, causing the PLGA controlled-release shell layer to release too quickly, making it difficult to achieve the three-stage stepped slow release. When the particle size of each spherical purifying agent particle is >5mm, it will cause the PLGA controlled-release shell layer to release too slowly and be difficult to mix evenly. In addition, each spherical purifying agent particle is not solid; there is a 20±3% gap between the core-shell structured microcapsule particles. These gaps absorb pressure like springs, and the pressure is transmitted through sliding between the particles, rather than directly compressing individual core-shell structured microcapsule particles.

[0142] S14. Surface activation treatment: At 150-180℃, 1-2 vol% SF6 / CO2 mixed gas is introduced to activate the initial purifying agent to obtain the purifying agent. The activation treatment time is 30-60 min.

[0143] Preferably, the total effective action time of the prepared purifying agent is 13 to 18 minutes.

[0144] In the embodiments of this application, 1-2 vol% SF6 / CO2 mixed gas means that the volume fraction of SF6 in the SF6 / CO2 mixed gas is 1-2 vol%.

[0145] It should be noted that during the surface activation process, SF6 will penetrate the PLGA controlled-release outer shell layer and react with the nano-magnesium oxide MgO in the core porous adsorption layer to generate a dense magnesium fluoride MgF2 protective film, thereby achieving fluorination modification of the purifier surface, effectively blocking moisture penetration, and ensuring that the purifier has a storage period of >18 months and a moisture absorption rate of <0.05% / d.

[0146] In this application, the purifying agent obtained needs to be sealed and stored, and the shelf life is >18 months and the moisture absorption rate is <0.05% / d when sealed and stored.

[0147] In this embodiment, the prepared purifying agent is stored in an aluminum foil bag, a sealed container, or a vacuum packaging method to prevent the purifying agent from absorbing moisture and oxidizing.

[0148] A third aspect of this invention provides a method for purifying magnesium alloy melt, which uses a purifying agent prepared by a method for preparing a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloy to purify the magnesium alloy melt, comprising the following steps:

[0149] S21. The solid magnesium alloy is melted at 700℃ under a 0.5 vol% SF6 / CO2 mixed atmosphere. After the solid magnesium alloy is completely melted, it is held at the temperature for 10-15 minutes. Then, the magnesium alloy melt is cooled to the semi-solid range of 560-620℃ at a cooling rate of 5℃ / min, so that the solid fraction of the magnesium alloy melt reaches 30-50%. Then, a purifying agent is added to the magnesium alloy melt, wherein the purifying agent accounts for 0.3-0.8 wt.% of the mass of the magnesium alloy melt.

[0150] In this embodiment of the application, 0.5 vol% SF6 / CO2 mixed atmosphere means that the volume fraction of SF6 in the SF6 / CO2 mixed atmosphere is 0.5 vol.

[0151] It should be noted that the 1-2 vol% SF6 / CO2 mixed gas in step S14 and the 0.5 vol% SF6 / CO2 mixed atmosphere in step S21 are essentially the same, but have different functions. Therefore, this application uses two different expressions. The 1-2 vol% SF6 / CO2 mixed gas emphasizes the combination of SF6 as a reactant gas and CO2 as a carrier gas, with a high concentration of SF6 (1-2%) used for chemical activation reaction to generate a MgF2 film; the 0.5 vol% SF6 / CO2 mixed atmosphere emphasizes a protective atmosphere, with a low concentration of SF6 (0.5%) used for melt oxidation protection (too high a concentration would lead to melt contamination).

[0152] In this application, when the magnesium alloy melt is cooled to a semi-solid range of 560 to 620°C, the solid fraction of the magnesium alloy melt is preferably 35% to 45%.

[0153] In this embodiment, the solid fraction refers to the volume or mass fraction of the solid phase in the semi-solid slurry. When the solid fraction of the magnesium alloy melt is 30-50%, the slurry will contain 30-50 wt.% of solid phase. The slurry consists of Mg particles, with the remainder being a liquid phase (enriched with elements such as Al and Mn). In this state, the slurry exhibits thixotropic properties, meeting the requirements of the purification process. If the solid fraction of the magnesium alloy melt is <30%, problems such as excessive liquid phase content, easy particle sedimentation, and uneven dispersion of the purifying agent will occur. If the solid fraction of the magnesium alloy melt is >50%, problems such as excessive viscosity, difficulty in stirring, and insufficient contact between the purifying agent and the melt will occur.

[0154] It should be noted that the solid fraction is constrained by both alloy composition and temperature, and is a passive function of temperature, not an independently settable process parameter. In the embodiments of this application, the target solid fraction is achieved indirectly by controlling the melt temperature, rather than by directly controlling the solid fraction.

[0155] S22. The magnesium alloy melt with added purifying agent is mechanically stirred, and then pulsed power ultrasonic treatment is performed after the mechanical stirring is completed.

[0156] In this application, during mechanical stirring, the rotation speed is 200–400 rpm and the stirring time is 5–10 min; during pulsed power ultrasonic treatment, the ultrasonic frequency is 20–40 kHz and the power density is 30 W / cm³. 2 The ultrasonic treatment time is 10-15 minutes, and the ultrasonic working mode is intermittent with a duty cycle of 1:1.

[0157] In this application, the macroscopic mixing of the purifying agent and the magnesium alloy melt is achieved through mechanical stirring; and the microscopic dispersion and cavitation degassing of the purifying agent and the magnesium alloy melt are achieved through pulsed power ultrasonic treatment.

[0158] S23. After the pulsed power ultrasonic treatment is completed, let it stand for 3-5 minutes, then remove the slag and stop the introduction of the 0.5 vol% SF6 / CO2 mixed atmosphere to obtain the purified magnesium alloy melt.

[0159] The fourth aspect of this invention provides a method for manufacturing magnesium alloy components. The method involves injection molding a magnesium alloy melt treated by a magnesium alloy melt purification method to obtain the magnesium alloy component. Specifically, the purified magnesium alloy melt is water-cooled or mist-cooled to 550-580°C at a cooling rate of 10-20°C / min under a 0.5 vol% SF6 / CO2 mixed atmosphere to obtain a semi-solid slurry. The 0.5 vol% SF6 / CO2 mixed atmosphere is then stopped, and the semi-solid slurry is used to prepare the magnesium alloy component using an injection molding process.

[0160] In this application, a 0.5 vol% SF6 / CO2 mixed atmosphere is continuously introduced from the purification of the magnesium alloy melt, without interruption between the magnesium alloy melt purification step and the magnesium alloy component manufacturing step, until a semi-solid slurry is obtained and then the mixed atmosphere is stopped.

[0161] It should be noted that the magnesium alloy melt purification method describes "after standing for 3-5 minutes, remove the slag and stop the introduction of the 0.5 vol% SF6 / CO2 mixed atmosphere," while the magnesium alloy component manufacturing method describes "under the protection of the 0.5 vol% SF6 / CO2 mixed atmosphere, water-cool or mist-cool the purified magnesium alloy melt to 550-580℃ at a cooling rate of 10-20℃ / min." However, it should be understood that the above descriptions are only for the purpose of distinguishing between the magnesium alloy melt purification method and the magnesium alloy component manufacturing method. When this method is applied to the actual process, the magnesium alloy melt directly enters the magnesium alloy component manufacturing process after purification, and the 0.5 vol% SF6 / CO2 mixed atmosphere is continuously introduced without interruption between the magnesium alloy melt purification step and the magnesium alloy component manufacturing step, until the semi-solid slurry is prepared before stopping the introduction of the mixed atmosphere.

[0162] It should be noted that in the traditional semi-solid forming process of low-aluminum magnesium alloys, there are two main methods for purifying the magnesium alloy melt: First, when the magnesium alloy melt is in the liquid range (usually 700-750℃), a traditional purifying agent (i.e., liquid purifying agent - RJ-2 flux) is added for purification. After purification, the magnesium alloy melt is cooled to the semi-solid range (560-620℃) and then injection molding is performed. Second, the liquid pre-purification step is omitted, and RJ-2 flux, originally designed for liquid casting, is used directly in the semi-solid injection temperature range for in-situ purification. However, both methods have significant drawbacks. For the first method, although the flux has high activity and relatively good purification effect in the liquid phase, the melt is exposed to high temperatures for a prolonged period during the cooling to semi-solid state, making it prone to secondary oxidation and gas absorption. Simultaneously, settled inclusions may be resuspended or new phases precipitate, leading to a partial reversal of the purification effect. For the second method, although the process is simplified and avoids secondary heating and cooling, the RJ-2 flux has significantly insufficient activity in the semi-solid range (560–620℃), a short effective action time (only 3–5 minutes), and poor density matching, making it difficult to achieve sufficient wetting and separation of inclusions, and easily introducing slag inclusion defects. Therefore, regardless of the method used, traditional RJ-2 flux struggles to balance purification effect and process stability, failing to meet the high requirements for melt purity and consistency in semi-solid injection molding of low-aluminum magnesium alloys.

[0163] Therefore, this application, targeting the semi-solid injection molding process, employs a rare earth-alkaline earth metal chloride-fluoride composite molten salt system and coaxial electrospray microcapsule encapsulation technology to specifically design a purifying agent for the semi-solid region. This not only avoids the re-oxidation problem caused by cooling after liquid purification but also achieves in-situ purification in the semi-solid region (560–620°C) for the first time. Furthermore, the step-wise slow-release mechanism of this purifying agent perfectly matches the semi-solid region, with three stages of release corresponding to pre-purification, main purification, and deep degassing.

[0164] In this embodiment of the application, when the semi-solid slurry is injected into a magnesium alloy component using the injection molding process, a semi-solid molding machine is used for injection, the injection speed is 2.0 m / s, the mold temperature is 280°C, the holding pressure is 100 MPa, and the holding time is 8 s.

[0165] Preferably, the solid phase content of the semi-solid slurry is 50-65%.

[0166] In this embodiment, the purified magnesium alloy melt is water-cooled or mist-cooled to 550-580°C at a cooling rate of 10-20°C / min. This is to ensure that the magnesium alloy melt has a sufficient temperature gradient to achieve rapid cooling after purification, preventing the regeneration of removed inclusions (secondary oxidation) and maintaining the clean state after purification. On the other hand, it is to increase the solid fraction of the magnesium alloy melt from 30-50% to 50-65%, obtaining the semi-solid slurry required for the semi-solid injection molding process, which meets the subsequent filling and forming requirements.

[0167] Preferably, the corrosion rate of the obtained magnesium alloy component is reduced by 45-65%, and the average removal rate of inclusions is 90.9%.

[0168] Preferably, the magnesium alloy component obtained has an inclusion removal rate of ≥88.0% and a hydrogen content of ≤9 cm⁻¹. 3 / 100g, tensile strength ≥278MPa, yield strength ≥175MPa, elongation ≥14.5%, corrosion rate ≤0.32mm / y, flux residue ≤0.040%.

[0169] Based on the aforementioned high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys, its preparation method, magnesium alloy melt purification method, and magnesium alloy component manufacturing method, this invention conducted comparative experiments across multiple dimensions to verify the purification advantages of the purifying agent provided by this invention. It should be noted that all raw materials used in the following experiments were commercially available.

[0170] First dimension: Comparison of purification effects of different purifying agent components on alloys of the same composition.

[0171] This dimension aims to verify the synergistic effect mechanism among the components in the purifier provided by this invention, and the influence of the ratio of key components on the purification effect. Examples 1 and Comparative Examples 11-16 all used AZ31B magnesium alloy (Al 3.0 wt.%, Zn 1.0 wt.%) melt as the base material (melt quantity 30 kg, magnesium alloy plate component dimensions 200 mm × 150 mm × 6 mm), maintaining consistent melting temperature, casting process, and other conditions. The effects of a complete formulation (Example 1), missing single components (Comparative Examples 11-13), unoptimized rare earth ratio (Comparative Example 14), and microcapsule shell thickness control (Comparative Examples 15-16) on the purification effect were systematically compared. The content of each component in the purifiers of the multiple examples and comparative examples involved in this dimension of the invention is shown in Table 1, and the preparation process is detailed below.

[0172]

[0173] Preparation process of Example 1

[0174] I. Preparation of Purifying Agent

[0175] S11. Raw material pretreatment, wherein the process parameters for each raw material pretreatment are shown in Table 2.

[0176]

[0177] S12. Microcapsule Encapsulation: Based on the pretreated core purification components and microcapsule encapsulation components, an inner- and outer-phase suspension was prepared, followed by the fabrication of core-shell structured microcapsule particles using coaxial electrospray scattering technology. Specifically:

[0178] S121. Preparation of internal phase suspension: The pretreated core purification component is mixed with nano-magnesium oxide (MgO) to obtain a first mixed powder. The first mixed powder is then added to anhydrous ethanol and ultrasonically dispersed at a frequency of 40 kHz for 30 min to obtain an internal phase suspension. The solid-liquid mass ratio of the first mixed powder to anhydrous ethanol is 1 g: 3.0 mL.

[0179] S122. Preparation of external phase suspension: The pretreated polylactic acid-glycolic acid copolymer (PLGA) was dissolved in dichloromethane (CH2Cl2) and magnetically stirred at 600 rpm for 4 hours to obtain an external phase suspension, wherein the concentration of polylactic acid-glycolic acid copolymer (PLGA) in the external phase suspension was 10 wt.%.

[0180] S123. Set the coaxial electrospray process parameters: the flow rate of the inner phase suspension is 0.80 mL / h, the flow rate of the outer phase suspension is 2.0 mL / h, the working voltage is 18.0 kV, the receiving distance is 18 cm, the inner diameter of the inner nozzle is 0.4 mm, and the inner diameter of the outer nozzle is 1.2 mm.

[0181] S124. Three-stage temperature control for preparing core-shell structured microcapsule particles: A coaxial electrospray device is used to simultaneously draw in the inner phase suspension and the outer phase suspension. Then, a three-stage temperature control setting is activated for coaxial electrospray to obtain core-shell structured microcapsule particles. The inner nozzle delivers the inner phase suspension, and the outer nozzle delivers the outer phase suspension. The coaxial electrospray device consists of a nozzle section, a flight section, and a receiving section. The three-stage temperature control setting is as follows: the nozzle section temperature is 45℃, the flight section temperature is 25℃, and the receiving section temperature is 8℃.

[0182] S125. Post-processing: The obtained core-shell structured microcapsule particles were vacuum dried at 40℃ for 12h with a vacuum degree of -0.092MPa.

[0183] S13. Ultrasonic-assisted granulation: The obtained core-shell structured microcapsule particles are mixed with auxiliary purification components, subjected to continuous power ultrasonic treatment, and then pressed into shape to obtain the initial purification agent, specifically:

[0184] S131. Mixing treatment: The obtained core-shell structured microcapsule particles, sodium bicarbonate NaHCO3, and pretreated calcium fluoride CaF2, sodium carbonate Na2CO3 and cryolite Na3AlF6 are mixed to obtain a second mixed powder.

[0185] S132. Continuous Power Ultrasonic Treatment: The second mixed powder is subjected to continuous power ultrasonic treatment, wherein the ultrasonic frequency is 30kHz and the power density is 40W / cm³. 2 The ultrasonic treatment time was 12.5 min;

[0186] S133, Compression molding: The second mixed powder after continuous power ultrasonic treatment is compressed into a spherical mold to obtain the initial purifying agent. The compression pressure is 200MPa, the holding time is 20s, and the diameter of the spherical mold is 4mm.

[0187] S14. Surface activation treatment: The initial purifying agent is activated by passing a 1.5 vol% SF6 / CO2 mixed gas through a gas at 165℃ to obtain the purifying agent. The activation treatment time is 45 min.

[0188] II. Magnesium Alloy Melt Purification

[0189] S21. Solid magnesium alloy is melted at 700℃ under a 0.5 vol% SF6 / CO2 mixed atmosphere. After the solid magnesium alloy is completely melted, it is held at that temperature for 12.5 min, and then cooled to a semi-solid temperature of 590℃ at a cooling rate of 5℃ / min, so that the solid phase content of the magnesium alloy melt is 40%. Then, a purifying agent is added to the magnesium alloy melt, wherein the purifying agent accounts for 0.6 wt.% of the mass of the magnesium alloy melt.

[0190] S22. The magnesium alloy melt with added purifying agent is mechanically stirred at 300 rpm for 8 minutes. After mechanical stirring, pulsed power ultrasonic treatment is performed. During pulsed power ultrasonic treatment, the ultrasonic frequency is 28 kHz and the power density is 30 W / cm³. 2 The ultrasonic treatment time is 10 minutes, and the ultrasonic working mode is intermittent with a duty cycle of 1:1.

[0191] S23. After the pulsed power ultrasonic treatment is completed, let it stand for 4 minutes, then remove the slag and stop the introduction of the 0.5 vol% SF6 / CO2 mixed atmosphere to obtain the purified magnesium alloy melt.

[0192] III. Manufacturing of Magnesium Alloy Components

[0193] Under the protection of a 0.5 vol% SF6 / CO2 mixed atmosphere, the purified magnesium alloy melt was water-cooled to 550°C at a cooling rate of 15°C / min to obtain a semi-solid slurry. Then, the 0.5 vol% SF6 / CO2 mixed atmosphere was stopped, and the semi-solid slurry was used to prepare magnesium alloy sheet components by injection molding.

[0194] In this experiment, a purifying agent was prepared based on the content of each component in the purifying agent and the preparation process of the purifying agent in Example 1. Its macroscopic morphology is as follows: Figure 1 As shown. From Figure 1 It can be clearly seen that the purifying agent consists of uniform white spherical particles with a uniform particle size distribution, regular appearance, smooth surface, and no obvious cracks or damage.

[0195] To verify the removal effect of the purifying agent obtained in Example 1 on inclusions in magnesium alloy melt, SEM observations were performed on magnesium alloy sheet components prepared directly using the preparation process of Example 1 without purifying the magnesium alloy melt, and on magnesium alloy sheet components prepared using the preparation process of Example 1 after purifying the magnesium alloy melt with the purifying agent obtained in Example 1. Figure 2-9 As shown, where, Figure 2-5 SEM images of inclusions in magnesium alloy sheet components obtained directly using the preparation process of Example 1 without using a purification agent to clean the magnesium alloy melt, with magnifications of 200x, 300x, 500x, and 1000x respectively; Figure 6-9 The images show the SEM morphology of inclusions in magnesium alloy sheet components prepared using the purifying agent obtained in Example 1 and then processed using the preparation process of Example 1. The magnifications are 200x, 300x, 500x, and 1000x, respectively.

[0196] from Figure 2-5It is evident that without the use of a purifying agent, the magnesium alloy melt contains a large number of densely distributed inclusions, exhibiting a network or dendritic distribution. These inclusions are relatively large in size and irregular in shape, with a high number and wide coverage per unit area. Figure 6-9 It is evident that after purification with the purifying agent obtained in Example 1, the number of inclusions in the magnesium alloy melt is significantly reduced, the size of the residual inclusions is significantly reduced, their distribution is sparse, and the area covered by inclusions per unit area is greatly reduced. Therefore, the purifying agent and magnesium alloy melt purification method provided by this invention can effectively remove inclusions from magnesium alloy melt, significantly reduce the number of inclusions, reduce the size of inclusions, and shrink the distribution area of ​​inclusions, demonstrating excellent purification effect.

[0197] Preparation process of Comparative Example 11

[0198] Unlike the preparation process of Example 1, Comparative Example 11 does not contain polylactic acid-glycolic acid copolymer (PLGA). Therefore, in the preparation of the purifying agent, microcapsule encapsulation was not performed in step S12. Only the step of "mixing the pretreated core purifying component with nano-magnesium oxide (MgO) to obtain the first mixed powder" was performed. The "core-shell structured microcapsule particles" used in step S13 were replaced with the "first mixed powder".

[0199] Preparation process of Comparative Example 12

[0200] Unlike the preparation process of Example 1, Comparative Example 12 does not contain rare earth chloride RECl3, so the treatment steps related to rare earth chloride RECl3 were not performed in steps S11 and S12 when preparing the purifying agent.

[0201] Preparation process of Comparative Example 13

[0202] Unlike the preparation process of Example 1, Comparative Example 13 does not contain nano-magnesium oxide (MgO). Therefore, in the preparation of the purifying agent, the step of "mixing the pretreated core purifying component with nano-magnesium oxide (MgO)" was not performed in step S121. Instead, the pretreated core purifying component was directly added to anhydrous ethanol and ultrasonically dispersed at a frequency of 40 kHz for 30 min to obtain an internal phase suspension. The solid-liquid mass ratio of the pretreated core purifying component to anhydrous ethanol was 1 g: 3.0 mL.

[0203] Preparation process of Comparative Example 14

[0204] The preparation methods for the purifying agent, the purification method for the magnesium alloy melt, and the manufacturing method for the magnesium alloy components are the same as those in Example 1.

[0205] Preparation process of Comparative Example 15

[0206] Unlike the preparation process in Example 1, in Comparative Example 15, the flow rate of the external phase suspension was 1.9 mL / h and the pressing pressure was 220 MPa when preparing the purifying agent.

[0207] It should be noted that the flow rate of the external phase suspension in Comparative Example 15 was set to a low value to match the characteristics of the purifying agent used (low PLGA fast-release formulation). Furthermore, given the low PLGA content and thin PLGA controlled-release outer shell of the polylactic acid-glycolic acid copolymer, appropriately increasing the pressing pressure ensures that each spherical purifying agent particle has sufficient mechanical strength (compressive strength ≥ 5 MPa) to prevent breakage during transportation and feeding, while maintaining a porosity of 20 ± 3% to ensure melt permeability. Therefore, a medium-to-high pressing pressure was used in Comparative Example 15.

[0208] Preparation process of Comparative Example 16

[0209] Unlike the preparation process in Example 1, in Comparative Example 16, the flow rate of the external phase suspension was 2.1 mL / h and the activation treatment time was 60 min when preparing the purifying agent.

[0210] It should be noted that the high flow rate of the external phase suspension in Comparative Example 16 was chosen to match the characteristics of the purifying agent (high PLGA slow-release formulation) used. Furthermore, since extending the activation treatment time thickens the magnesium fluoride protective film, further delaying the initial release rate of PLGA degradation in the polylactic acid-glycolic acid copolymer and enhancing the slow-release effect, a high activation treatment time was also chosen in Comparative Example 16.

[0211] Second dimension: Comparison of purification effects of the same purifying agent on alloys of different compositions.

[0212] This dimension aims to verify the universality of the purifying agent provided by this invention for alloys with different compositions. In all embodiments under this dimension, except for the alloy composition, semi-solid temperature, and solid fraction of the magnesium alloy melt, which differ from Example 1, the content of each component in the purifying agent, the preparation method, the magnesium alloy melt purification method, and the magnesium alloy component manufacturing method are all the same as the specific preparation process in Example 1. The differences in purification temperature for each alloy are determined based on its liquidus temperature and target solid fraction (approximately 40%), to verify the adaptability of the purifying agent under different semi-solid temperature conditions. The alloy compositions and semi-solid temperatures in the multiple embodiments involved in this dimension are shown in Table 3.

[0213]

[0214] Third dimension: Purification comparison between the purifying agent provided by this invention and commonly used traditional purifying agents.

[0215] This dimension aims to verify the purification advantages of the purifier provided by this invention compared to commonly used traditional purifiers. This dimension also uses Example 1 from the first dimension as a benchmark, comparing its purification effect with that of commonly used traditional purifiers.

[0216] Comparative Example 21

[0217] Unlike Example 1, the purifying agent used in the magnesium alloy melt purification process was commercial RJ-2 flux. The content of each component in the purifying agent was: anhydrous magnesium chloride MgCl2 44wt.%, anhydrous potassium chloride KCl 36wt.%, anhydrous sodium chloride NaCl 12wt.%, and anhydrous calcium chloride CaCl2 8wt.%. The purification preparation method was as follows: the components were mechanically mixed in proportion, vacuum dried at 300℃ for 4h (vacuum degree ≤ -0.095MPa), then crushed and sieved to a particle size ≤ 2mm, and sealed for storage.

[0218] Comparative Example 22

[0219] I. Preparation of Purifying Agent

[0220] The purifying agent used was commercial RJ-2 flux. The contents of each component in the purifying agent were: anhydrous magnesium chloride MgCl2 44wt.%, anhydrous potassium chloride KCl 36wt.%, anhydrous sodium chloride NaCl 12wt.%, and anhydrous calcium chloride CaCl2 8wt.%. The specific preparation method was as follows: the components were mechanically mixed in proportion, vacuum dried at 300℃ for 4h (vacuum degree ≤ -0.095MPa), then crushed and sieved to a particle size ≤ 2mm, and sealed for storage.

[0221] II. Magnesium Alloy Melt Purification

[0222] S21. Solid magnesium alloy was melted at 700℃ under a 0.5 vol% SF6 / CO2 mixed atmosphere. After the solid magnesium alloy was completely melted, it was held at this temperature for 12.5 min. Then, commercial RJ-2 flux was added to the magnesium alloy melt at a liquid temperature of 700℃, wherein the flux accounted for 0.6 wt.% of the mass of the magnesium alloy melt.

[0223] S22. The magnesium alloy melt with commercial RJ-2 flux was mechanically stirred at 300 rpm for 8 minutes. After mechanical stirring, it was subjected to pulsed power ultrasonic treatment. During pulsed power ultrasonic treatment, the ultrasonic frequency was 28 kHz and the power density was 30 W / cm³. 2 The ultrasonic treatment time is 10 minutes, and the ultrasonic working mode is intermittent with a duty cycle of 1:1.

[0224] S23. After the pulsed power ultrasonic treatment is completed, let it stand for 4 minutes, then remove the slag and stop the introduction of the 0.5 vol% SF6 / CO2 mixed atmosphere to obtain the purified magnesium alloy melt.

[0225] III. Manufacturing of Magnesium Alloy Components

[0226] Under the protection of a 0.5 vol% SF6 / CO2 mixed atmosphere, the liquid purified magnesium alloy melt was water-cooled to 560°C at a cooling rate of 15°C / min to obtain a semi-solid slurry. Then, the 0.5 vol% SF6 / CO2 mixed atmosphere was stopped, and the semi-solid slurry was used to prepare magnesium alloy sheet components by injection molding.

[0227] It should be noted that the difference between Comparative Example 22 and Comparative Example 21 is that Comparative Example 21 directly applies commercial RJ-2 flux to the semi-solid region to verify whether the flux can play a purifying role under semi-solid conditions; while Comparative Example 22 applies commercial RJ-2 flux to a traditional liquid purification process (700℃) and then cools it to the semi-solid region to simulate the "liquid refining → transfer → cooling" process path commonly used in traditional foundries, thereby verifying the applicability of this path in the semi-solid injection molding process.

[0228] Comparative Example 23

[0229] Unlike Example 1, the purifying agent used in the magnesium alloy melt purification process is a single sodium carbonate foaming agent, and the component content in the purifying agent is: sodium carbonate Na2CO3 100wt.%.

[0230] Comparative Example 24

[0231] Unlike Example 1, no purifying agent was used in the magnesium alloy melt purification process; pure argon was used for refining. Specifically, step S21 involved melting a solid magnesium alloy at 700°C under a 0.5 vol% SF6 / CO2 mixed atmosphere. After complete melting, the solid magnesium alloy was held at this temperature for 12.5 minutes. Then, the magnesium alloy melt was cooled to a semi-solid temperature of 590°C at a cooling rate of 5°C / min, resulting in a solid fraction of 40%. A purifying agent was then added to the magnesium alloy melt. The protective atmosphere was then switched to pure argon, and pure argon was introduced into the bottom of the magnesium alloy melt at a flow rate of 5 L / min for refining for 10 minutes. After pure argon refining, the protective atmosphere was switched back to a 0.5 vol% SF6 / CO2 mixed atmosphere. The purifying agent comprised 0.6 wt.% of the magnesium alloy melt mass.

[0232] Comparative Example 25

[0233] Unlike Example 1, no purifying agent was used in the magnesium alloy melt purification process; pure physical filtration (ceramic filtration) was employed. Specifically, step S21 involved melting a solid magnesium alloy at 700°C under a 0.5 vol% SF6 / CO2 mixed atmosphere. After complete melting, the solid magnesium alloy was held at this temperature for 12.5 minutes. Then, the magnesium alloy melt was cooled to a semi-solid temperature of 590°C at a cooling rate of 5°C / min, resulting in a solid fraction of 40%. A purifying agent was then added to the magnesium alloy melt, and the melt was physically filtered through an alumina ceramic filter plate (20 ppi pore size, 25 mm thickness) pre-installed in the transfer path. The purifying agent comprised 0.6 wt.% of the magnesium alloy melt mass.

[0234] Comparative Example 26

[0235] Unlike Example 1, the purifying agent used in the magnesium alloy melt purification process is hexachloroethane (C2Cl6), and the component content of the purifying agent is: hexachloroethane (C2Cl6) 100 wt.%.

[0236] It should be noted that hexachloroethane (C2Cl6) has been listed in the "Guidance Catalogue for Industrial Structure Adjustment" as an eliminated substance, and is a substance whose use is expressly prohibited by the state. Its use as a comparative example in this invention is solely for the purpose of more intuitively and fully demonstrating the progress and advantages of the present invention's technical solution compared to existing technologies; it does not constitute an endorsement of its use value, nor does it constitute any usage advice.

[0237] In this experiment, the commercially available RJ-2 flux used in Comparative Examples 21-22 was prepared using a standard process that simulated the flux. The sodium carbonate foaming agent used in Comparative Example 23 and the hexachloroethane C2Cl6 used in Comparative Example 26 were both commercially available reagents.

[0238] Fourth dimension: Verification of the purification effect of the optimal component content of the purifying agent under various combinations of process parameters within the process parameter window.

[0239] This dimension aims to verify the purification agent with the optimal component ratio of the present invention. Within the process parameter window defined by the present invention, when the process parameters for preparing the purification agent are combined in different combinations within their allowable ranges, the purification effect remains stable and excellent. The experiment used the optimal component content of the present invention (i.e., the content of each component in Example 1) as a fixed formula, and the process parameter range defined by the present invention as the operating conditions. Arbitrary combinations of each process parameter were conducted at their upper limit, lower limit, and recommended values ​​to systematically examine the influence of arbitrary combinations within the parameter range on the purification effect. Meanwhile, the magnesium alloy melt purification method and magnesium alloy component manufacturing method in all examples and comparative examples under this dimension are the same as in Example 1. Multiple sets of examples and comparative examples of the present invention under this dimension are shown in Table 4.

[0240]

[0241]

[0242] Fifth dimension: Verification of the purification effect of the optimal purification agent preparation process at different concentrations of purification agent components.

[0243] This dimension aims to verify the tolerance of the optimal purification agent preparation process of the present invention to fluctuations in component content, that is, to examine whether the purification agent prepared using the optimal preparation process of the present invention can still maintain excellent purification effect when the component content of the purification agent varies within a limited range. The experiment used the optimal preparation process of the present invention (i.e., the purification agent preparation process in Example 1) as a fixed condition, and the component content parameter range defined by the present invention as the operating condition. Arbitrary combinations of each component content parameter were conducted at its upper limit, lower limit, and recommended value to systematically examine the influence of arbitrary combinations within the parameter range on the purification effect. Meanwhile, the magnesium alloy melt purification method and magnesium alloy component manufacturing method in all embodiments under this dimension are the same as in Example 1. Multiple embodiments of the present invention under this dimension are shown in Table 5.

[0244]

[0245] Sixth dimension: Verification of the purification effect of the purifying agent prepared with optimal component content and optimal preparation process within the range of process parameters for melt purification and magnesium alloy component manufacturing.

[0246] This dimension aims to verify whether the purification effect remains excellent when the purification agent prepared using the optimal component content and optimal preparation process of this invention is used in the magnesium alloy melt purification process and the magnesium alloy component manufacturing process, and when the process parameters are combined in different ways within the range defined by this invention. Using the purification agent prepared with the optimal component content and optimal preparation process of this invention (i.e., the component content and preparation process of the purification agent in Example 1) as a fixed condition, and the magnesium alloy melt purification process and magnesium alloy component manufacturing process defined by this invention as the operating conditions, experiments were conducted on the parameters in this process using arbitrary combinations at their upper limit, lower limit, and intermediate values. The influence of arbitrary combinations of parameters within the parameter range on the purification effect was systematically examined. Multiple embodiments of this invention in this dimension are shown in Table 6.

[0247]

[0248] It should be noted that Example 1 in the first, second, third, fourth, and sixth dimensions refers to the same example, and is cited in multiple dimensions for ease of comparison. Furthermore, the magnesium alloy component manufacturing method involved in this application is a conventional process; its innovation lies solely in the fact that the magnesium alloy melt used is obtained after treatment by a magnesium alloy melt purification method. Therefore, the sixth dimension mainly examines the impact of arbitrary combinations of process parameters within the parameter range on the purification effect.

[0249] Performance tests: inclusion removal rate test, hydrogen content test, room temperature tensile properties test, corrosion weight loss test under 3.5wt.% NaCl solution for 72h, and flux residue test.

[0250] In this experiment, metallographic image analysis / electrolytic extraction was used to detect the inclusion removal rate. The inclusion removal rate was obtained by comparing the number and area fraction of inclusions per unit area in the magnesium alloy melt before and after purification. The hydrogen content was detected by vacuum extraction (Ransley method). Mechanical properties, such as tensile strength, yield strength, and elongation, were detected by room temperature tensile testing. The tensile rate in the room temperature tensile test was 2 mm / min, and the test results were taken as the average value of three samples. The flux residue rate was detected by chemical dissolution-inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0251] In this experiment, flux residue rate refers to the ratio of the total mass of the purifying agent (flux) remaining in the magnesium alloy melt after purification to the initial mass of the purifying agent added.

[0252] In this experiment, the specific method for testing the flux residue rate was as follows: After purification and slag removal, a quantitative sample of magnesium alloy melt was taken, chemically dissolved, and then the total content of elements such as Mg, K, Ca, Na, Al, and F was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). This content was converted into the mass of the purifying agent residue and compared with the initial mass of the purifying agent to obtain the flux residue rate. The lower the flux residue rate, the better the separation effect between the purifying agent and the magnesium alloy melt, and the lower the risk of secondary pollution.

[0253] In this application, performance tests were conducted on magnesium alloy sheet components obtained from all embodiments and comparative examples in the first to sixth dimensions. The performance test results of the embodiments and comparative examples in the first dimension are shown in Table 7, the performance test results of the embodiments in the second dimension are shown in Table 8, the performance test results of the embodiments and comparative examples in the third dimension are shown in Table 9, the performance test results of the embodiments and comparative examples in the fourth dimension are shown in Table 10, the performance test results of the embodiments in the fifth dimension are shown in Table 11, and the performance test results of the embodiments in the sixth dimension are shown in Table 12.

[0254]

[0255] Example 1 is the baseline formulation of this invention, therefore, Example 1 is used as a reference in this experiment for comparison with Comparative Examples 11-16. Table 7 clearly shows that Example 1, through the stepwise degradation of polylactic acid-glycolic acid copolymer (PLGA), achieves the phased and continuous release of the purification components, thus significantly extending the purification time and ensuring thorough purification of the melt, resulting in balanced overall performance. Comparative Example 11, lacking PLGA, produces a purification agent without a PLGA controlled-release shell layer. Each component is rapidly released and reacts quickly after being added to the melt, resulting in a short purification duration (4-5 minutes), leading to insufficient purification and degassing. Consequently, its inclusion removal rate is much lower than that of Example 1, and its hydrogen content is much higher. Furthermore, due to the inclusions... Insufficient removal further leads to a decrease in mechanical properties, an increase in corrosion rate and flux residue, thus confirming that microencapsulated sustained release is key to efficient purification. In Comparative Example 12, due to the absence of rare earth chlorides RECl3 (i.e., lanthanum chloride LaCl3 and cerium chloride CeCl3), the prepared purifier lacks sufficient affinity for oxide inclusions such as Al2O3 and ZnO, resulting in inadequate deep purification, high inclusion residue, and overall performance deterioration. This confirms that rare earth chlorides RECl3 are the core of deep purification. In Comparative Example 13, due to the absence of nano-magnesium oxide MgO, the prepared purifier lacks a core porous adsorption layer, and the specific surface area of ​​the core decreases to 5m². 2 The capture efficiency of suspended oxide inclusions decreased by 9.5% compared to Example 1, which also indirectly affected the degassing effect. This confirms that the active adsorption effect of nano-magnesium oxide (MgO) in the core is irreplaceable and is the key to improving purification efficiency. Therefore, "polylactic acid-glycolic acid copolymer (PLGA) + rare earth chloride (RECl3) + nano-magnesium oxide (MgO)" are the three key mechanisms for effective removal of inclusions in this invention: slow-release mechanism, deep purification mechanism, and active adsorption mechanism. The synergy of these three mechanisms can achieve an inclusion removal rate of 93.0%, far exceeding the inclusion removal rate of any single mechanism.

[0256] In Comparative Example 14, the mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) was 1:1, exceeding the range defined in this application (1.5–2.5:1). This resulted in an excessively high activity of cerium (Ce) and a relatively insufficient activity of lanthanum (La) in the prepared purifying agent (cerium ions Ce). 3+ Due to its smaller ionic radius and higher charge density, it exhibits stronger chemical reactivity than the lanthanum ion (La). 3+ Therefore, given a mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) of 1:1, the cerium ion (Ce)... 3+ It will be more than lanthanum ion La 3+It exhibits stronger catalytic activity and a faster reaction rate. When cerium (Ce) activity is too high, it reacts indiscriminately with various oxide inclusions (Al2O3, ZnO, MgO, etc.), resulting in a rapid consumption rate and an inability to selectively remove high-melting-point, highly hazardous Al2O3 inclusions. Simultaneously, when lanthanum (La) activity is relatively insufficient, it cannot form a La-Ce synergistic adsorption complex, leading to a higher density of the purified product (rare earth oxides / aluminates) and a decrease in flotation separation efficiency. Therefore, a 1:1 mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) results in decreased purification selectivity (i.e., the purifier fails to efficiently and directionally act on the target inclusions, but is consumed in large quantities by non-target reactions, with some effective components being depleted prematurely), thus reducing purification efficiency. This further confirms the importance of limiting the mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) to 1.5–2.5:1 in this application, and that 2:1 is the preferred mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3).

[0257] In Comparative Example 15, the content of nano-magnesium oxide (MgO) was set to a high value, the content of polylactic acid-glycolic acid copolymer (PLGA) to a low value, the pressing pressure to a medium-high value, and the flow rate of the external phase suspension to a low value, resulting in a low-PLGA fast-release formulation. The thickness of the PLGA controlled-release outer shell layer of the core-shell structured microcapsule particles was the thinnest among Examples 1 and Comparative Examples 11-16. Table 7 shows that although the inclusion removal rate decreased by 2.7% compared to Example 1, its inclusion removal efficiency was still much higher than that of Comparative Example 11. Simultaneously, compared to Example 1, the elongation of Comparative Example 15 increased to 16.7%, indicating that moderately reducing the PLGA content of polylactic acid-glycolic acid copolymer can achieve an optimized balance between purification efficiency and plasticity. Therefore, the low-PLGA fast-release formulation can achieve an optimized balance between time efficiency and purification effect, making it suitable for large-scale rapid production.

[0258] In Comparative Example 16, the content of nano-magnesium oxide (MgO) was set to a low value, the content of polylactic acid-glycolic acid copolymer (PLGA) to a high value, the flow rate of the external phase suspension to a high value, and the activation treatment time to a high value, resulting in a high PLGA sustained-release formulation. The thickness of the PLGA controlled-release outer shell layer of the core-shell structured microcapsule particles was the thickest in Examples 1 and Comparative Examples 11-16. As can be seen from Table 7, its inclusion removal rate was increased by 2.2% compared to Example 1, and except for the elongation (due to the thick PLGA controlled-release outer shell layer, some incompletely degraded PLGA residues had a slight negative impact on plasticity), all its properties were optimal. Therefore, the high PLGA sustained-release formulation can achieve the longest effective action time, the highest purification efficiency, the lowest hydrogen content and corrosion rate, and the highest strength, making it the optimal choice for achieving high quality.

[0259] Furthermore, Table 7 shows a significant positive correlation between corrosion rate and the amount of residual inclusions. Comparative Example 12, lacking deep rare earth purification, had the most residual inclusions and the highest corrosion rate (0.52 mm / y), an increase of 116.7% compared to Example 1. Comparative Example 16, with the highest inclusion removal rate, had the lowest corrosion rate (0.18 mm / y), a decrease of 25.0% compared to Example 1. This further confirms that inclusions (especially oxide and chloride residues) are the main cathodic active sites for magnesium alloy corrosion, and efficient removal of inclusions can give the finished product excellent corrosion resistance.

[0260] Furthermore, the combination of "polylactic acid-glycolic acid copolymer (PLGA) + rare earth chloride (RECl3) + nano-magnesium oxide (MgO)" is a key factor in achieving low flux residue in this invention. Specifically, the PLGA controlled-release shell, formed by the PLGA copolymer, ensures that the reaction products are easily separated and floated after the purifying agent reacts fully with the melt; the low-density rare earth oxides generated by the reaction of rare earth chloride (RECl3) with the oxides are easily separated by flotation; and the porous adsorption layer formed by nano-magnesium oxide (MgO) actively captures inclusions, reducing flux entrainment. As shown in Table 7, the flux residue rate in Comparative Example 11 is as high as 0.065%, an increase of 132.1% compared to Example 1, indicating that the PLGA controlled-release shell plays a crucial role in promoting the separation and flotation of the purifying agent. Comparative Example 16 has the lowest flux residue (0.022%), further verifying that the thick-shell slow-release mechanism can reduce flux residue caused by localized supersaturation.

[0261]

[0262] As can be seen from Table 8, the inclusion removal efficiency is the best in Example 1, and its overall performance is balanced. Therefore, the purifier provided by the present invention is suitable for the purification of AZ31B magnesium alloy melt.

[0263] Example 2 was applied to the purification of AZ40 magnesium alloy melt (this magnesium alloy has a higher Al content than AZ31B magnesium alloy). Its inclusion removal rate was slightly lower than that of Example 1, but its tensile strength and yield strength were significantly improved. This is because when the Al content increased from 3.0 wt.% to 3.5 wt.%, it was still within the solid solution strengthening-dominated range and had not yet reached the critical value for large-scale β-phase precipitation (approximately 6 wt.%). Therefore, while appropriately increasing the Al content may increase the purification difficulty, it can significantly improve the mechanical properties of the finished product without causing obvious embrittlement. This confirms that the purifier provided by this invention is suitable for the purification of AZ40 magnesium alloy melt, and further confirms that the purifier provided by this invention is suitable for the purification of AZ-based magnesium alloy melt.

[0264] Example 3 was applied to the purification of AZ61A magnesium alloy melt, where the Al content reached 6.0 wt.%, close to the upper limit of application of this invention. High Al content not only increases the tendency for alumina inclusions to form in the melt but also increases the melt viscosity; the combined effect significantly increases the difficulty of purification. As shown in Table 8, the inclusion removal rate of Example 3 was 90.5%, a decrease of 2.7% compared to Example 1, but still maintaining a high purification level. Its tensile strength was 300 MPa and its yield strength was 220 MPa, slightly lower than Examples 1 and 2. This is not due to insufficient purification effect, but rather because when the Al content is too high (6.0 wt.%), Mg… 17 Al 12 The brittle (β-phase) phase precipitates extensively at grain boundaries in a continuous network, leading to grain boundary embrittlement. Although solid solution strengthening still exists, the negative effects of the brittle phase dominate, resulting in lower intrinsic mechanical properties of AZ61A magnesium alloy compared to AZ31B and AZ40 magnesium alloys. This indicates that there is an optimal range for Al content in AZ-based magnesium alloys (approximately 3.0–4.0 wt.%). Beyond this range, even with good purification, the precipitation of brittle phases caused by excessive Al will lower the upper limit of the intrinsic mechanical properties of the finished product. Furthermore, the purification agent provided in this invention can still achieve a 90.5% inclusion removal rate under high Al content conditions, significantly improving the actual performance of AZ61A magnesium alloy and further confirming that the obtained purification agent is suitable for purifying high-Al AZ-based magnesium alloys.

[0265] Example 4 was applied to the purification of AM60B magnesium alloy melt (this type of magnesium alloy has high Al and Mn content, good castability, high ductility, and Al-Mn compounds are easy to form inclusion sources). The inclusion removal rate was reduced by 1.9% compared to Example 1, but it could still effectively remove Al-Mn inclusions, and its elongation reached the optimal level. Therefore, the purifying agent provided by this invention is suitable for purifying AM60B magnesium alloy melt, and when applied to this type of magnesium alloy, the finished product can maintain extremely high elongation and exhibit good plasticity.

[0266] Example 5 was applied to the purification of AM50A magnesium alloy melt (this magnesium alloy has an Al content of 4.8 wt.% and a Mn content of 0.35 wt.%, with the Al-Mn compound inclusion formation amount between that of AM60B magnesium alloy and AZ-based magnesium alloys). The inclusion removal rate was 91.8%, an increase of 0.7% compared to Example 4, confirming that a lower Al content is beneficial for reducing the total Al-Mn inclusion formation and improving purification efficiency. Simultaneously, the inclusion removal rate was 18.2%, second only to Example 4, further confirming the excellent plasticity characteristics of AM-based magnesium alloys. Therefore, the purifying agent provided by this invention is suitable for the purification of AM50A magnesium alloy melt, and further confirms that the purifying agent provided by this invention is suitable for the purification of AM-based magnesium alloy melt, and that when applied to AM-based magnesium alloys, it can achieve a good synergistic balance between purification efficiency and plasticity.

[0267] Example 6 was applied to the purification of AS31B magnesium alloy melt. The inclusion removal rate decreased by 3.8% compared to Example 1, while the hydrogen content significantly increased. This indicates that the presence of Si not only increases the purification difficulty but also leads to a decrease in degassing efficiency (Mg2Si particles have a density close to that of the magnesium matrix and are hard and brittle, making them difficult to remove by being carried away by rising bubbles, and also hindering the escape path of hydrogen bubbles). This invention removes Mg2Si by adding calcium fluoride (CaF2), allowing the fluoride ions in CaF2 to react with silicate inclusions in the magnesium alloy melt to generate volatile SiF4 gas. For AS-based magnesium alloys, this reaction can be achieved with a calcium fluoride (CaF2) content in the range of 12–14 wt.%. In Example 6, the calcium fluoride (CaF2) content was 13 wt.%, and the inclusion removal rate still reached 89.5%, confirming that the purifier provided by this invention is also suitable for the purification of AS-based magnesium alloy melts.

[0268] Example 7 was applied to the purification of AS41B magnesium alloy melt (the Al content of this magnesium alloy is 4.0 wt.%, higher than that of AS31B magnesium alloy). The inclusion removal rate was reduced by 5.2% compared to Example 1, and the hydrogen content reached the highest among Examples 1-7. This confirms that the superimposed effect of high Al content and Si element will further increase the purification difficulty. However, the inclusion removal rate still reached 88.2%, confirming that the purification agent provided by the present invention is also suitable for the purification of AS41B magnesium alloy melt, and can still maintain an effective purification effect in AS-based magnesium alloys with high Al content. At the same time, its tensile strength is 278 MPa and its yield strength is 205 MPa. This shows that when the purification agent provided by the present invention is applied to AS41B magnesium alloy, especially AS-based magnesium alloys with high Al content, the mechanical properties are still maintained within an acceptable range.

[0269] Furthermore, Table 8 shows that the average inclusion removal rate of the seven alloys was 91.0%, and the average hydrogen content was 7.9 cm³.3 The average corrosion rate per 100g is 0.27mm / y, indicating that the purifying agent provided by this invention has excellent versatility and is suitable for various magnesium alloy systems.

[0270] It should be noted that this experiment used typical alloys such as AZ31B (Al 2.5–3.5 wt.%), AZ40 (Al 3.0–4.0 wt.%), AZ61A (Al 5.5–6.5 wt.%), AM60B (Al 5.5–6.5 wt.%), AM50A (Al 4.4–5.4 wt.%), AS31B (Al 2.5–3.5 wt.%), and AS41B (Al 3.5–4.5 wt.%) as experimental subjects to verify the purification effect of the obtained purifying agent. The results show that this method has good applicability to AZ-based, AM-based, and AS-based magnesium alloys with Al content of 2.5–6.5 wt.%. In addition, for AZ-based, AM-based, and AS-based magnesium alloys with Al content of 2.0–2.5 wt.%, since their purification mechanism is consistent with the aforementioned alloys, the purifying agent obtained by this method is also applicable. Therefore, the purifying agent obtained by this method is suitable for AZ-based, AM-based and AS-based magnesium alloys with an Al content of 2.0 to 6.5 wt.%.

[0271]

[0272] As shown in Table 9, compared with Example 1, Comparative Example 21 showed a 37.1% decrease in inclusion removal rate, a 226.1% increase in hydrogen content, a 16.9% decrease in tensile strength, a 28.0% decrease in elongation, a 158.3% increase in corrosion rate, and a 489.3% increase in flux residue. This is because the purifying agent used in Comparative Example 21 was commercial RJ-2 flux, which lacks rare earth chloride RECl3 and thus lacks deep chemical affinity for oxide inclusions such as Al2O3 and ZnO; it lacks a microcapsule controlled-release structure, making it unable to achieve staged slow release in the semi-solid region; and it lacks a nano-magnesium oxide (MgO) physical adsorption layer, making it unable to actively capture suspended inclusions. Furthermore, the density of commercial RJ-2 flux is close to that of molten magnesium alloy, making effective separation difficult and resulting in a flux residue of up to 0.165%, which easily leads to secondary pollution. Simultaneously, commercial RJ-2 flux is suitable for the liquid casting zone, but in Comparative Example 21, it was directly used in the semi-solid zone, leading to incomplete decomposition of its active components and further exacerbating the low purification efficiency. Therefore, it is clear that the purification effect of commercial RJ-2 flux is unsatisfactory, and it is incompatible with the semi-solid casting zone.

[0273] Comparative Example 22 also used commercial RJ-2 flux, but employed the traditional "liquid purification (700℃) followed by cooling" process. Although the commercial RJ-2 flux exhibited higher activity at 700℃, with a slightly better purification effect than Comparative Example 21, confirming the activity advantage of commercial RJ-2 flux in the liquid casting zone, the melt was exposed to a high-temperature environment for an extended period during the cooling process, leading to secondary oxidation and gas absorption. This resulted in the purified melt being recontaminated, causing the final performance to be significantly inferior to Example 1. Therefore, Comparative Example 22 further demonstrates that even with the traditional liquid purification process, commercial RJ-2 flux, lacking the synergistic mechanism of the "polylactic acid-glycolic acid copolymer PLGA + rare earth chloride RECl3 + nano-magnesium oxide MgO" of this invention, still cannot meet the melt purity requirements of the semi-solid injection molding process. Furthermore, Comparative Example 22 further highlights the core value of this invention: it not only solves the problem of flux activity in the semi-solid zone but also effectively avoids secondary contamination caused by cooling through in-situ purification.

[0274] The purifying agent used in Comparative Example 23 was a single sodium carbonate foaming agent. Compared with Example 1, the inclusion removal rate of Comparative Example 23 decreased by 47.7%, the tensile strength decreased by 19.2%, and the elongation decreased by 29.9%. It can be seen that a single foaming agent can only physically degas and has no chemical purification effect, and cannot effectively remove oxide inclusions.

[0275] In Comparative Example 24, no purifying agent was used; the mixture was refined with pure argon. Compared to Example 1, the removal rate of inclusions decreased by 51.0%, and the hydrogen content increased by 168.1%. This indicates that argon can only remove some gases and floating inclusions, and is ineffective against suspended oxides, thus having no chemical purification effect.

[0276] In Comparative Example 25, no purifying agent was used; instead, ceramic filtration (pure physical filtration) was employed. Compared to Example 1, the removal rate of inclusions decreased by 26.5%, and the hydrogen content increased by 139.1%. This demonstrates that pure physical filtration can only remove inclusions larger than the filter pore size and is ineffective against fine inclusions and gases, thus having no chemical purification effect.

[0277] Comparative Example 26 used hexachloroethane (C2Cl6), which is now banned. Compared to Example 1, its inclusion removal rate decreased by 62.2%, tensile strength decreased by 21.2%, elongation decreased by 37.8%, corrosion rate increased by 225.0%, and it emitted a large amount of toxic Cl2 and CCl4 gases (banned by environmental regulations). This shows that hexachloroethane (C2Cl6) alone can only remove gases and cannot remove any oxide inclusions. It also easily produces a large amount of toxic gases and is therefore unusable.

[0278] Therefore, compared with traditional purification methods, the purification agent provided by the present invention exhibits superior performance in terms of inclusion removal rate, hydrogen content, mechanical properties, plasticity, and corrosion resistance; at the same time, according to the flux residue rate in Table 9, the purification agent provided by the present invention causes minimal secondary pollution.

[0279] It should be noted that in this application, "chemical purification" refers to the targeted removal of inclusions by reacting the components of the purifying agent with oxides and sulfides in the melt to generate low-density compounds or soluble complexes.

[0280] It should be noted that the purifying agent provided by this invention completely eliminates toxic substances such as hexachloroethane (C2Cl6) that have been listed as eliminated in the "Guidance Catalogue for Industrial Structure Adjustment (2024 Edition)". It adopts a sodium carbonate-sodium bicarbonate composite foaming system, which achieves environmentally friendly degassing and meets the requirements of green manufacturing.

[0281]

[0282] As can be seen from Table 10, Example 1 achieved the best overall performance due to the adoption of a median process design, indicating that the purification effect is best when the parameters are at the median value within the range of process parameters defined by this invention. Example 8, due to the adoption of a low-value process design, resulted in insufficient drying, a thinner shell layer, and insufficient granulation, which led to a slight decrease in purification performance. Example 9, due to the adoption of a high-value process design, resulted in excessive drying, causing sintering of some components and incomplete degradation of the shell layer, thus its purification performance was also slightly lower than that of Example 1. Examples 10-12 were mixed combinations of different process parameters, and their purification performance was between that of Examples 8 and 9, confirming that within the range of purification agent preparation process parameters defined by this invention, any combination of parameters can maintain a good purification effect.

[0283] In Comparative Example 31, the vacuum degree, moisture target, particle size parameter, and receiving distance of most materials exceeded the upper limit of the parameter range, aiming to verify the comprehensive impact of multiple key process parameters exceeding the limit simultaneously on the purification effect. In Comparative Example 32, the vacuum degree, moisture target, and particle size parameter of all materials were taken as boundary values, while the working voltage exceeded the upper limit of the parameter range, aiming to verify the stability of the purification effect when the process parameters are at the boundary, and the impact of a single key parameter exceeding the range on the purification effect. As can be seen from Table 10, in Comparative Example 31, the microcapsule structure was severely damaged due to the vacuum degree, moisture target, particle size parameter, and receiving distance of most materials exceeding the upper limit of the parameter range, resulting in an inclusion removal rate of 82.0%. In Comparative Example 32, the microcapsule structure was basically intact but slightly defective due to the vacuum degree, moisture target, particle size parameter, and working voltage of all materials being taken at boundary values ​​and the working voltage being too high. The inclusion removal rate was 85.0%, which was better than that of Comparative Example 31, but significantly lower than the lowest inclusion removal rate in Examples 1 and 8-12. This confirms that when multiple key process parameters simultaneously exceed the limit, their inhibitory effect on the purification effect is significantly greater than that of a single parameter exceeding the limit. Furthermore, the process parameter range defined by this invention is a necessary condition to ensure the performance of the purifying agent.

[0284] It should be noted that in Comparative Example 31, the vacuum degree, moisture target, and particle size parameters of most materials have exceeded the upper limit of the parameter range, and the conclusion that exceeding the boundary is not feasible has been fully verified. The vacuum degree, moisture target, and particle size parameters of a small number of materials have not exceeded the upper limit of the parameter range, which does not affect the verification purpose.

[0285]

[0286] As can be seen from Table 11, the inclusion removal rate of Examples 13-21 is ≥88.0%, and the hydrogen content is ≤9 cm⁻¹. 3 The composition of the purifier, measured per 100g, exhibits tensile strength ≥278MPa, yield strength ≥175MPa, elongation ≥14.5%, corrosion rate ≤0.32mm / y, and flux residue ≤0.040%, demonstrating superior performance in terms of inclusion removal rate, hydrogen content, mechanical properties, plasticity, corrosion resistance, and flux residue. This indicates that within the component content range defined by this invention, any combination of components can maintain a good purification effect.

[0287] The inclusion removal rate, hydrogen content, tensile strength, yield strength, corrosion rate, and flux residue rate of Example 19 were the best among Examples 13-21, indicating that the purification efficiency and separation effect can be optimally balanced under this set of proportions. The inclusion removal rate, hydrogen content, tensile strength, yield strength, corrosion rate, and flux residue rate of Example 15 were the worst among Examples 13-21, confirming that cerium Ce excess (relative cerium Ce excess when the mass ratio of lanthanum chloride LaCl3 to cerium chloride CeCl3 is 1.5:1) leads to a decrease in purification selectivity.

[0288] The inclusion removal rate of Example 20 is better than that of Example 13, but the hydrogen content and flux residue rate are similar to those of Example 13. This indicates that when the content of rare earth chloride RECl3, the mass ratio of lanthanum chloride LaCl3 and cerium chloride CeCl3, and the content of auxiliary purification components are the same, increasing the content of the core purification components can improve the purification efficiency, and that excessively high content of auxiliary purification components (the content of auxiliary purification components in Examples 13 and 20 both reached the highest level) will restrict further improvement in degassing and separation effects.

[0289] The inclusion removal rate, hydrogen content, tensile strength, yield strength, corrosion rate, and flux residue rate of Example 19 are all superior to those of Example 17, indicating that when the mass ratio of lanthanum chloride (LaCl3) and cerium chloride (CeCl3) is the same, increasing the content of the core purification component and the rare earth chloride (RECl3) content, as well as decreasing the content of the microcapsule-coated component, can significantly improve the purification efficiency and separation effect. Meanwhile, the flux residue rate of Example 19 is the same as that of Example 1, indicating that a high core purification component content combined with a high lanthanum content can achieve the optimal balance between purification efficiency and separation effect.

[0290] Example 16 showed better performance than Example 18 in terms of inclusion removal rate, hydrogen content, tensile strength, yield strength, corrosion rate, and flux residue rate. This indicates that, with the same rare earth chloride (RECl3) content and the same mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3), increasing the content of the core purification component can improve purification efficiency. Furthermore, in Example 18, the excessively high content of the microcapsule-coated component led to incomplete degradation of the purifier and a delayed release rate, resulting in inferior performance compared to Example 16.

[0291] Example 19 showed better inclusion removal rate, hydrogen content, tensile strength, yield strength, corrosion rate, and flux residue rate than Example 21. This indicates that, with the same rare earth chloride (RECl3) content, increasing the content of the core purification component, increasing the mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3), and reducing the content of the microcapsule coating component can further improve purification efficiency and reduce hydrogen content. It also confirms the superiority of a lanthanum chloride (LaCl3) to cerium chloride (CeCl3) mass ratio of 2.5:1. Furthermore, because the content of the auxiliary purification component in Example 21 was lower than that in Example 19, the foaming degassing effect was limited, resulting in a higher hydrogen content than in Example 19.

[0292] The inclusion removal rate of Example 14 is close to that of Example 19, but the other performance is poor. This indicates that when the content of the core purification component is too high and the content of the auxiliary purification component and the microcapsule coating component is too low, the purification efficiency will be close to the optimal level, but its degassing and separation effects will be limited.

[0293]

[0294] As can be seen from Table 12, Example 1 achieved optimal overall performance due to its median process design. Example 22, with its low-value process design, resulted in insufficient initial release of polylactic acid-glycolic acid copolymer (PLGA) and a low amount of purifying agent, leading to incomplete purification, a low inclusion removal rate, and a high hydrogen content. Example 23, with its high-value process design, used a large amount of purifying agent, increasing costs and causing excessive stirring, which slightly increased melt oxidation. Therefore, its overall performance was slightly lower than that of Example 1. This demonstrates the necessity of the magnesium alloy melt purification process parameters defined in this invention. In industrial production, the median parameters should be prioritized. When fine-tuning parameters is necessary due to production cost constraints, multiple parameters should not be selected at their lower limits simultaneously, otherwise, incomplete purification may result.

[0295] Furthermore, in Examples 1 and 22-23, the inclusion removal rate was ≥88.0%, and the hydrogen content was ≤9 cm⁻¹. 3 The properties of the purifying agent ( / 100g), tensile strength ≥278MPa, yield strength ≥175MPa, elongation ≥14.5%, corrosion rate ≤0.32mm / y, and flux residue ≤0.040% also demonstrate that the purifying agent provided by this invention exhibits superior performance in terms of inclusion removal rate, hydrogen content, mechanical properties, plasticity, corrosion resistance, and flux residue. Therefore, it can be seen that within the range of magnesium alloy melt purification process parameters defined by this invention, any combination of parameters can maintain a good purification effect.

[0296] In summary, this invention, by employing a rare earth-alkaline earth metal chloride-fluoride composite molten salt system and coaxial electrospray microcapsule encapsulation technology, not only solves the technical problems of excessively rapid decomposition, low purification efficiency, re-oxidation, and poor environmental performance of traditional purifiers in the semi-solid injection molding process of low-aluminum magnesium alloys, but also provides a highly efficient, universal, environmentally friendly, and economical purification solution for the semi-solid injection molding process of low-aluminum magnesium alloys, with significant engineering application value and economic benefits.

[0297] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys, characterized in that, The raw material components are composed of the following mass percentages: 60-69 wt.% core purification component, 23-28 wt.% auxiliary purification component, and 8-12 wt.% microcapsule coating component. The core purification component includes anhydrous magnesium chloride (MgCl2), anhydrous potassium chloride (KCl), anhydrous calcium chloride (CaCl2), and rare earth chloride (RECl3). The auxiliary purification component includes calcium fluoride (CaF2), sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), and cryolite (Na3AlF6). The microcapsule coating component includes nano-magnesium oxide (MgO) and polylactic acid-glycolic acid copolymer (PLGA). The rare earth chloride (RECl3) is a mixture of lanthanum chloride (LaCl3) and cerium chloride (CeCl3), with a mass ratio of 1.5-2.5:

1. The purifying agent is formed by pressing auxiliary purification components and core-shell structured microcapsule particles. The core-shell structured microcapsule particles consist of a core, a porous core adsorption layer, and a PLGA controlled-release outer shell layer covering the porous core adsorption layer. The core is formed by the core purification component; the porous core adsorption layer is a porous layer of nano-magnesium oxide (MgO) formed by the electrostatic self-assembly of MgO onto the core surface. The thickness of the porous core adsorption layer is 10–15 μm, and its specific surface area is >80 m². 2 / g; The PLGA controlled-release outer shell is formed by coating the porous adsorption layer of the core with polylactic acid-glycolic acid copolymer PLGA through a phase separation method, and the thickness is 20-30μm.

2. The high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys according to claim 1, characterized in that, Magnesium alloys are AZ-based, AM-based, and AS-based magnesium alloys with an Al content of 2.0–6.5 wt.%. In the core purification components, anhydrous magnesium chloride (MgCl2) accounts for 28–30 wt.%, anhydrous potassium chloride (KCl) accounts for 16–18 wt.%, anhydrous calcium chloride (CaCl2) accounts for 10–14 wt.%, and rare earth chloride (RECl3) accounts for 6–8 wt.%. In the auxiliary purification components, calcium fluoride (CaF2) accounts for 12–14 wt.%, sodium carbonate (Na2CO3) accounts for 6–7 wt.%, sodium bicarbonate (NaHCO3) accounts for 3–4 wt.%, and cryolite (Na3AlF6) accounts for 2–3 wt.%. In the microcapsule coating components, nano-magnesium oxide (MgO) accounts for 5–7 wt.% and polylactic acid-glycolic acid copolymer (PLGA) accounts for 3–5 wt.%.

3. The high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys according to claim 2, characterized in that, The particle size of nano-magnesium oxide (MgO) is 50–200 nm, and the purity is ≥99.9%; the molecular weight of polylactic acid-glycolic acid copolymer (PLGA) is 50,000–100,000, and the molar ratio of lactic acid to glycolic acid is 75:

25.

4. The high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys according to claim 3, characterized in that, The mass ratio of lanthanum chloride (LaCl3) to cerium chloride (CeCl3) is 2:

1.

5. A method for preparing a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys, characterized in that, The preparation of the high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys according to any one of claims 1-4 includes the following steps: S11, Raw material pretreatment; S12, Microcapsule Coating: Based on the pretreated core purification components and microcapsule coating components, an inner and outer phase suspension was prepared, and then core-shell structured microcapsule particles were prepared using coaxial electrospray technology. S13, Ultrasonic-assisted granulation: The obtained core-shell structured microcapsule particles are mixed with auxiliary purification components, subjected to continuous power ultrasonic treatment, and then pressed into shape to obtain the initial purification agent. S14. Surface activation treatment: At 150-180℃, 1-2 vol% SF6 / CO2 mixed gas is introduced to activate the initial purifying agent to obtain the purifying agent. The activation treatment time is 30-60 min.

6. The method for preparing a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys according to claim 5, characterized in that, Step S11 is as follows: S111. Anhydrous magnesium chloride (MgCl2) was vacuum dried at 320±10℃ for 5.0±0.5h, with a vacuum degree <-0.095MPa, and the moisture content after vacuum drying was <0.03%. S112. Anhydrous potassium chloride (KCl) was vacuum dried at 300±10℃ for 4.0±0.5h, with a vacuum degree <-0.095MPa, and the moisture content after vacuum drying was <0.02%. S113. Anhydrous calcium chloride (CaCl2) was vacuum dried at 350±10℃ for 6.0±0.5h, with a vacuum degree <-0.095MPa, and the moisture content after vacuum drying was <0.05%. S114. The rare earth chloride RECl3 was vacuum dried at 250±10℃ for 4.0±0.5h, with a vacuum degree of <-0.090MPa. After the vacuum drying process, it was ground. The moisture content after vacuum drying was <0.10%, and the particle size of the ground rare earth chloride RECl3 was <100μm. S115. Calcium fluoride (CaF2) is dried at 120±5℃ under normal pressure for 2.0±0.5h. The moisture content after drying is <0.10%. S116. Sodium carbonate (Na2CO3) was dried at 110±5℃ under normal pressure for 2.0±0.5h, and the moisture content after drying was <0.15%. S117. Cryolite Na3AlF6 was dried at 135±5℃ under normal pressure for 2.0±0.5h, and the moisture content after drying was <0.10%; S118. Nano-sized magnesium oxide (MgO) is vacuum dried at 120±5℃ for 2.0±0.5h, with a vacuum degree <-0.090MPa, and the moisture content after drying is <0.10%. S119. Polylactic acid-glycolic acid copolymer (PLGA) was vacuum dried at 40±2℃ for 12 hours, with a vacuum degree < -0.090MPa, and the moisture content after drying was <0.05%. Step S12 is as follows: S121. Preparation of internal phase suspension: The pretreated core purification component is mixed with nano-magnesium oxide (MgO) to obtain a first mixed powder. The first mixed powder is then added to anhydrous ethanol and ultrasonically dispersed at a frequency of 40 kHz for 30 min to obtain an internal phase suspension. The solid-liquid mass ratio of the first mixed powder to anhydrous ethanol is 1 g: 2.5-3.5 mL. S122. Preparation of external phase suspension: The pretreated polylactic acid-glycolic acid copolymer (PLGA) was dissolved in dichloromethane (CH2Cl2) and magnetically stirred at 600 rpm for 4 hours to obtain an external phase suspension, wherein the concentration of PLGA in the external phase suspension was 8–12 wt.%. S123. Set the coaxial electrospray process parameters: the flow rate of the inner phase suspension is 0.8±0.05mL / h, the flow rate of the outer phase suspension is 2.0±0.1mL / h, the working voltage is 18±0.5kV, the receiving distance is 18±1cm, the inner diameter of the inner nozzle is 0.4mm, and the inner diameter of the outer nozzle is 1.2mm. S124. Three-stage temperature control for preparing core-shell structured microcapsule particles: A coaxial electrospray device is used to simultaneously draw in the inner phase suspension and the outer phase suspension. Then, a three-stage temperature control setting is activated for coaxial electrospray to obtain core-shell structured microcapsule particles. The inner nozzle delivers the inner phase suspension, and the outer nozzle delivers the outer phase suspension. The coaxial electrospray device consists of a nozzle section, a flight section, and a receiving section. The three-stage temperature control setting is as follows: the nozzle section temperature is 45±2℃, the flight section temperature is 25±3℃, and the receiving section temperature is 8±2℃. S125. Post-processing: The obtained core-shell structured microcapsule particles were vacuum dried at 40±2℃ for 12h, with a vacuum degree of <-0.090MPa. Step S13 is as follows: S131. Mixing treatment: The obtained core-shell structured microcapsule particles, sodium bicarbonate NaHCO3, and pretreated calcium fluoride CaF2, sodium carbonate Na2CO3 and cryolite Na3AlF6 are mixed to obtain a second mixed powder. S132. Continuous Power Ultrasonic Treatment: The second mixed powder is subjected to continuous power ultrasonic treatment, wherein the ultrasonic frequency is 20–40 kHz and the power density is 30–50 W / cm³. 2 The duration of ultrasonic treatment is 10–15 minutes; S133, Compression molding: The second mixed powder after continuous power ultrasonic treatment is compressed into a spherical mold to obtain the initial purifying agent. The compression pressure is 150-259 MPa, the holding time is 10-30 s, and the diameter of the spherical mold is 3-5 mm.

7. The method for preparing a high-efficiency purifying agent for low-aluminum semi-solid injection magnesium alloys according to claim 6, characterized in that, After the microcapsule encapsulation process, the residual amount of anhydrous ethanol is <100ppm and the residual amount of dichloromethane (CH2Cl2) is <50ppm. The prepared core-shell structured microcapsule particles consist of a core, a porous core adsorption layer, and a PLGA controlled-release outer shell layer coating the porous core adsorption layer. The core is formed by the core purification component; the porous core adsorption layer is a porous layer of MgO nano-oxide formed by the electrostatic self-assembly of MgO nano-oxide onto the core surface, with a thickness of 10–15 μm and a specific surface area >80 m². 2 / g; The PLGA controlled-release outer shell is formed by coating the porous adsorption core layer with polylactic acid-glycolic acid copolymer PLGA through a phase separation method, and the thickness is 20-30μm. The obtained core-shell structured microcapsule particles have a microcapsule yield of >85%, an encapsulation rate of >95%, and a D50 particle size of 120±20μm. The initial purifying agent consists of multiple particles with a uniform spherical appearance; each spherical purifying agent particle has a particle size of 3-5 mm, a porosity of 20±3%, and a compressive strength ≥5 MPa; The total effective action time of the prepared purifying agent is 13-18 minutes.

8. A method for purifying magnesium alloy melt, characterized in that, The purification treatment of magnesium alloy melt using the purification agent prepared by the method of preparing a high-efficiency purification agent for low-aluminum semi-solid injection magnesium alloy according to any one of claims 5-7 includes the following steps: S21. Solid magnesium alloy is melted at 700℃ under a 0.5 vol% SF6 / CO2 mixed atmosphere. After complete melting, the solid magnesium alloy is held at this temperature for 10–15 minutes. Then, the magnesium alloy melt is cooled to a semi-solid range of 560–620℃ at a cooling rate of 5℃ / min, so that the solid fraction of the magnesium alloy melt reaches 30–50%. A purifying agent is then added to the magnesium alloy melt, wherein the purifying agent accounts for 0.3–0.8 wt.% of the mass of the magnesium alloy melt. S22. The magnesium alloy melt with added purifying agent is mechanically stirred, followed by pulsed power ultrasonic treatment. During mechanical stirring, the rotation speed is 200–400 rpm, and the stirring time is 5–10 min. During pulsed power ultrasonic treatment, the ultrasonic frequency is 20–40 kHz, and the power density is 30 W / cm³. 2 The ultrasonic treatment time is 10-15 minutes, and the ultrasonic working mode is intermittent with a duty cycle of 1:

1. S23. After the pulsed power ultrasonic treatment is completed, let it stand for 3-5 minutes, then remove the slag and stop the introduction of the 0.5 vol% SF6 / CO2 mixed atmosphere to obtain the purified magnesium alloy melt.

9. A method for manufacturing magnesium alloy components, characterized in that, Magnesium alloy components are obtained by injection molding of magnesium alloy melt treated by the magnesium alloy melt purification method described in claim 8. Specifically, the purified magnesium alloy melt is water-cooled or mist-cooled to 550-580°C at a cooling rate of 10-20°C / min under the protection of a 0.5 vol% SF6 / CO2 mixed atmosphere to obtain a semi-solid slurry. Then, the 0.5 vol% SF6 / CO2 mixed atmosphere is stopped, and the semi-solid slurry is prepared into magnesium alloy components by injection molding.

10. A method for manufacturing a magnesium alloy component according to claim 9, characterized in that, A 0.5 vol% SF6 / CO2 mixed atmosphere is continuously introduced from the magnesium alloy melt purification process, without interruption between the magnesium alloy melt purification step and the magnesium alloy component manufacturing step, until a semi-solid slurry is obtained and then the mixed atmosphere is stopped. The obtained magnesium alloy components have an inclusion removal rate of ≥88.0% and a hydrogen content of ≤9 cm⁻¹. 3 / 100g, tensile strength ≥278MPa, yield strength ≥175MPa, elongation ≥14.5%, corrosion rate ≤0.32mm / y, flux residue ≤0.040%.

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