Short process heat treatment process for magnesium alloys

Abstract

This application provides a short-process heat treatment process for magnesium alloys, belonging to the field of magnesium alloy preparation. The process includes: alloy casting of magnesium alloy raw materials to obtain a magnesium alloy ingot; the chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd: 6.51%–8.99%, Y: 0.8%–1.0%, Zr: 0.3%–0.5%, impurity elements ≤0.1%, Mg, Zn; solution treatment of the magnesium alloy ingot to obtain a solution-treated magnesium alloy; the solution treatment holding temperature is 460℃–480℃, and the holding time is 6h–8h; aging treatment of the solution-treated magnesium alloy to obtain an aged magnesium alloy; the aging treatment temperature is 200℃–210℃, and the time is 10–12h. This application, through the synergistic design of alloy composition and heat treatment process, significantly shortens the heat treatment process while achieving a good balance between strength and ductility in the magnesium alloy.

Description

Technical Field

[0001] This application relates to the field of magnesium alloy preparation technology, and in particular to a short-process heat treatment process for magnesium alloys. Background Technology

[0002] Magnesium alloys, as the lightest metallic structural materials, have shown enormous potential for lightweight applications in aerospace, new energy vehicles, low-altitude economy, and robotics, with cast magnesium alloys being the most widely used. One of the key factors that has long limited the large-scale application of cast magnesium alloys is the difficulty in simultaneously achieving both strength and ductility. Under traditional processes, increasing strength often comes at the cost of sacrificing ductility, and vice versa. Furthermore, strengthening magnesium alloy materials typically requires heat treatment, which is time-consuming and incurs high energy and time costs. Against this backdrop, the development of a short-process heat treatment technology for high-performance cast magnesium alloys (such as Mg-Gd-Y series) that combine excellent strength and ductility is not only a process optimization but also a key technology for overcoming the aforementioned bottlenecks, achieving significant improvements in material performance, and expanding application areas.

[0003] From the perspectives of engineering economics and green manufacturing, short-process heat treatment also offers significant advantages in industrial applications. Heat treatment is one of the most energy-intensive and time-consuming stages in the production chain of high-performance magnesium alloy components. Shortening the traditional heat treatment process, which can take tens of hours, results in a dramatic reduction in energy consumption, a significant increase in equipment utilization and turnover, and a substantial reduction in overall manufacturing costs. This is particularly important for price- and efficiency-sensitive applications. Furthermore, shortening the high-temperature treatment time can effectively reduce component deformation, lower internal stress, and control oxide layer thickness, thereby improving dimensional accuracy and surface quality, reducing subsequent machining allowances, and further meeting the demands of precision component manufacturing. Therefore, developing short-process heat treatment technologies for high-performance cast magnesium alloys has significant scientific and industrial value. Summary of the Invention

[0004] This application provides a short-process heat treatment process for magnesium alloys to solve the following technical problem: how to achieve a good balance between strength and ductility in magnesium alloys while significantly shortening the heat treatment process.

[0005] This application provides a short-process heat treatment process for magnesium alloys, the process including: Magnesium alloy raw materials are alloyed and cast to obtain magnesium alloy ingots; the chemical composition of the magnesium alloy ingots, by mass fraction, includes: Gd: 6.51%~8.99%, Y: 0.8%~1.0%, Zr: 0.3%~0.5%, impurity elements ≤0.1%, Mg, Zn; The magnesium alloy ingot is subjected to solution treatment to obtain a solution-treated magnesium alloy; the holding temperature of the solution treatment is 460℃~480℃, and the holding time is 6h~8h. The solid solution magnesium alloy is subjected to aging treatment to obtain an aged magnesium alloy; the aging treatment temperature is 200℃~210℃ and the time is 10~12h.

[0006] Optionally, the chemical components satisfy the following relationship: 1 / 25 ≤ [Zn] / ([Gd]+[Y]+[Zr]) ≤ 1 / 16 In the formula, [Zn] represents the mass fraction of Zn, [Gd] represents the mass fraction of Gd, [Y] represents the mass fraction of Y, and [Zr] represents the mass fraction of Zr.

[0007] Optionally, the process of alloying the magnesium alloy raw material to obtain a magnesium alloy ingot includes: Pure magnesium is melted under the combined protection of a mixture of CO2 and SF6 gas and a chloride flux to obtain magnesium melt; After the magnesium melt is heated to 740℃~750℃, magnesium gadolinium master alloy, magnesium yttrium master alloy and pure zinc are added in sequence. After all the magnesium melts, a homogenization treatment is performed to obtain the first melt. The first melt is heated to 770℃~780℃, and a magnesium-zirconium master alloy is added. After melting, a second homogenization treatment is performed to obtain the second melt. The second melt is refined, slag is removed, and the temperature is maintained for 10-12 minutes to obtain the third melt; The third melt is cooled to 720℃~730℃ and allowed to stand for 10 minutes before being cast to obtain a magnesium alloy ingot.

[0008] Optionally, the purity of the pure magnesium is ≥99.95%; The purity of the zinc is ≥99.995%; The rare earth element content in the magnesium-gadolinium master alloy, the magnesium-yttrium master alloy, and the magnesium-zirconium master alloy is 29% to 31% by mass fraction.

[0009] Optionally, both the primary homogenization process and the secondary homogenization process employ a combination of mechanical stirring and ultrasonic treatment. The frequency of the ultrasonic treatment is 18kHz to 22kHz, and the treatment time is 3min to 5min per treatment.

[0010] Optionally, the step of solution treatment of the magnesium alloy ingot to obtain a solution-treated magnesium alloy includes: The magnesium alloy ingot is heated to 420℃ to 440℃ at a heating rate of 14℃ / min to 16℃ / min, and held at that temperature for 5min to 10min. At a heating rate of 4℃ / min to 6℃ / min, the magnesium alloy ingot, after the first heat preservation, is heated to 460℃ to 480℃ for the second time and held for 6h to 8h. The magnesium alloy ingot after the second heat treatment is quenched to obtain a solid solution magnesium alloy.

[0011] Optionally, the quenching is water quenching, and the water temperature for water quenching is 70℃~80℃.

[0012] Optionally, the step of aging the solution-treated magnesium alloy to obtain an aged magnesium alloy includes: The solid solution magnesium alloy was heated to 170℃ to 190℃ at a heating rate of 14℃ / min to 16℃ / min, and then held at that temperature for 5min to 10min. At a heating rate of 4℃ / min to 6℃ / min, the solid solution magnesium alloy after the third holding is heated to 200℃ to 210℃ for the fourth time and held for 10h to 12h. The solid solution magnesium alloy after the fourth heat preservation was air-cooled to obtain an aged magnesium alloy.

[0013] Optionally, the total treatment time for the solution treatment and the aging treatment is 16h to 22h.

[0014] Optionally, the aged magnesium alloy meets the following properties: tensile strength ≥280MPa, yield strength ≥175MPa, and elongation ≥12%.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a short-process heat treatment process for magnesium alloys. Through the synergistic design of alloy composition and heat treatment process, the heat treatment process is significantly shortened while achieving a good balance between strength and ductility in the magnesium alloy.

[0016] In terms of alloy composition, the base is Gd (6.51%–8.99%), Y (0.8%–1.0%), and Zr (0.3%–0.5%), with an appropriate amount of Zn added. In this composition system, Gd plays a role in solid solution plasticization and precipitation strengthening, providing the main source of strength for the alloy; Y inhibits the coarsening of Mg-Gd nano-precipitates at high temperatures, ensuring the stability of the precipitates; Zr improves plasticity through grain refinement; and the appropriate addition of the key Zn element lowers the solution treatment temperature and shortens the solution treatment time by reducing the melting point of the second phase, while promoting the precipitation of nano-reinforcing phases during aging, thereby shortening the aging period.

[0017] In terms of heat treatment processes, a solution treatment at 460℃~480℃ for 6h~8h and an aging treatment at 200℃~210℃ for 10h~12h are employed. Thanks to the regulating effect of Zn, the solution treatment can achieve complete dissolution of alloying elements at relatively low temperatures and in a short time; the aging treatment, promoted by Zn, accelerates the uniform precipitation of nano-reinforcing phases, significantly shortening the aging cycle. The total time for solution treatment and aging treatment is controlled within the range of 16h~22h, greatly shortening the heat treatment process compared to traditional methods.

[0018] The synergistic effect of the aforementioned components and processes enabled the alloy to achieve a good balance between strength and ductility after short-process heat treatment: precipitation strengthening by Gd and stabilizing effect by Y ensured high strength; solid solution plasticizing by Gd, grain refinement strengthening by Zr, and appropriate addition of Zn prevented the formation of harmful phases, jointly guaranteeing excellent ductility. Ultimately, the aged magnesium alloy prepared by this process achieved comprehensive mechanical properties with a tensile strength ≥280MPa and an elongation ≥12%. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic flow diagram of a short-process heat treatment process for magnesium alloys provided in this application embodiment; Figure 2 This is a distribution diagram of nano-precipitated phases in an aged magnesium alloy matrix provided in Example 1 of this application; Figure 3This is a morphology diagram of the nano-precipitated phase in the aged magnesium alloy matrix provided in Example 1 of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0024] Figure 1 This is a schematic flow diagram of a short-process heat treatment process for magnesium alloys provided in an embodiment of this application.

[0025] like Figure 1 As shown in the embodiment of this application, a short-process heat treatment process for magnesium alloys is provided, the process including: S1. The magnesium alloy raw material is alloyed and cast to obtain a magnesium alloy ingot; the chemical composition of the magnesium alloy ingot by mass fraction includes: Gd: 6.51%~8.99%, Y: 0.8%~1.0%, Zr: 0.3%~0.5%, impurity elements ≤0.1%, Mg, Zn; S2. The magnesium alloy ingot is subjected to solution treatment to obtain a solution-treated magnesium alloy; the holding temperature of the solution treatment is 460℃~480℃, and the holding time is 6h~8h. S3. The solution-treated magnesium alloy is subjected to aging treatment to obtain an aged magnesium alloy; the aging treatment temperature is 200℃~210℃ and the time is 10~12h.

[0026] It should be noted that this application provides a short-process heat treatment process for magnesium alloys, which aims to obtain magnesium alloy materials with both high strength and excellent ductility by precisely controlling the synergistic effect between alloy composition and heat treatment parameters.

[0027] S1 involves alloy composition design and casting. The core of this step lies in providing a matrix material with good strength and toughness potential for subsequent short-process heat treatment through the synergistic regulation of multiple alloying elements. The chemical composition of the magnesium alloy ingot, by mass fraction, mainly includes Gd (6.51%–8.99%), Y (0.8%–1.0%), and Zr (0.3%–0.5%), with the total content of impurity elements not exceeding 0.1%, the balance being Mg, and an appropriate amount of Zn added. In this composition system, each alloying element plays a unique and synergistic role: Gd is the main strengthening and toughening element, mainly playing a role in "solid solution plasticization" and "precipitation strengthening," providing a foundation for high strength in the alloy; the addition of Y can effectively suppress the coarsening tendency of Mg-Gd nano-precipitates at high temperatures, ensuring the stability of the precipitates; Zr improves the plasticity of the alloy through a grain refinement strengthening mechanism. The appropriate introduction of the key element Zn can firstly lower the melting point of the second phase by combining with Mg, Gd and Y elements to form the LPSO phase, thereby creating conditions for lowering the subsequent solid solution treatment temperature and shortening the solid solution time; at the same time, Zn can accelerate the precipitation of Mg-RE nano-reinforced phase during the aging process, thereby shortening the aging cycle. For example, the mass fraction of Gd can be 6.60%, 6.80%, 7.00%, 7.20%, 7.40%, 7.60%, 7.80%, 8.00%, etc.; the mass fraction of Y can be 0.82%, 0.84%, 0.86%, 0.88%, 0.90%, 0.92%, 0.94%, 0.96%, etc.; the mass fraction of Zr can be 0.32%, 0.34%, 0.36%, 0.38%, 0.40%, 0.42%, 0.44%, 0.46%, etc.; and the mass fraction of impurity elements can be 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, etc.

[0028] S2 is the solution treatment, which aims to dissolve as much of the second phase in the alloy as possible into the magnesium matrix, forming a supersaturated solid solution to prepare for subsequent aging precipitation. This process employs a short-process solution treatment, with a holding temperature of 460℃~480℃ and a holding time of 6h~8h. These temperature and time parameters are optimized based on the regulatory effect of Zn in step S1. Because the addition of Zn lowers the melting point of the second phase, the solution treatment can be carried out within a relatively low temperature range of 460℃~480℃, while the holding time is shortened to 6h~8h. This ensures sufficient dissolution of the alloying elements while significantly reducing energy consumption and production cycle. Performing the solution treatment within this temperature range effectively avoids the formation of more coarse needle-like Zn-Zr phases in the magnesium alloy matrix due to excessively high temperatures or long holding times, thus preventing the consumption of strengthening elements and the deterioration of the alloy's ductility. After solution treatment, quenching is performed using hot water at 70–80°C. The purpose is to quickly retain the supersaturated solid solution structure at high temperature, providing a good initial state for subsequent aging treatment. For example, the solution treatment temperature can be 462°C, 464°C, 466°C, 468°C, 470°C, 472°C, 474°C, 476°C, etc.; the holding time can be 6.2h, 6.4h, 6.6h, 6.8h, 7.0h, 7.2h, 7.4h, 7.6h, etc.

[0029] S3 refers to aging treatment, which decomposes the supersaturated solid solution and precipitates fine, dispersed nano-reinforcing phases, thus producing a significant precipitation strengthening effect on the alloy. The aging treatment temperature in this process is 200℃~210℃, and the holding time is 10~12h. This aging regime is closely related to the alloy composition and solid solution process. Within this temperature range, thanks to the promoting effect of Zn on precipitation, the uniform precipitation of the Mg-RE nano-reinforcing phase is accelerated, forming a... Figure 1 and Figure 2 The finely dispersed nano-reinforcements (approximately 10 nm in size) shown achieve significant strengthening effects within a short period of 10–12 hours. Simultaneously, controlling the aging temperature between 200°C and 210°C avoids coarsening of the nano-reinforcement phase due to excessively high temperatures or prolonged aging times, thus ensuring that the strengthening ability of the alloy is not weakened. For example, the aging treatment temperatures can be 201°C, 202°C, 203°C, 204°C, 205°C, 206°C, 207°C, 208°C, etc., and the holding times can be 10.2 h, 10.4 h, 10.6 h, 10.8 h, 11.0 h, 11.2 h, 11.4 h, 11.6 h, etc.

[0030] In summary, by precisely designing the content and ratio of Gd, Y, Zr, and Zn elements in step S1, and combining this with the low-temperature short-time solution treatment in step S2 and the medium-temperature effective aging in step S3, this series of process parameters forms an organic whole. This process fully leverages the synergistic mechanisms of Gd's solution plasticizing and precipitation strengthening, Y's inhibition of precipitate coarsening, Zr's grain refinement strengthening, and Zn's lowering of melting point and promotion of precipitation. Ultimately, while controlling the entire heat treatment process within the range of 16–22 hours, a magnesium alloy with both good strength and excellent ductility was successfully prepared, achieving a room-temperature tensile strength exceeding 280 MPa and an elongation exceeding 12%, thus achieving a good balance between excellent strength and ductility.

[0031] In some implementations, the chemical components satisfy the following relationship: 1 / 25 ≤ [Zn] / ([Gd]+[Y]+[Zr]) ≤ 1 / 16 In the formula, [Zn] represents the mass fraction of Zn, [Gd] represents the mass fraction of Gd, [Y] represents the mass fraction of Y, and [Zr] represents the mass fraction of Zr.

[0032] To maximize the synergistic effect of each element, the amount of Zn added must be strictly controlled to satisfy the relationship 1 / 25 ≤ [Zn] / ([Gd]+[Y]+[Zr]) ≤ 1 / 16. This range ensures that the amount of Zn added can exert its positive effects of lowering the melting point and promoting precipitation, while avoiding the formation of excessive LPSO phase and needle-like Zn-Zr-rich phase in the matrix due to excessive addition, thereby preventing the consumption of key strengthening elements such as Gd, Y, and Zr and weakening their strengthening effect. For example, [Zn] / ([Gd]+[Y]+[Zr]) can be 1 / 25, 1 / 22, 1 / 20, 1 / 18, 1 / 16, etc.

[0033] In some embodiments, alloy casting of magnesium alloy raw materials to obtain magnesium alloy ingots includes: Pure magnesium is melted under the combined protection of a mixture of CO2 and SF6 gas and a chloride flux to obtain magnesium melt; After the magnesium melt is heated to 740℃~750℃, magnesium gadolinium master alloy, magnesium yttrium master alloy and pure zinc are added in sequence. After all the magnesium melts, a homogenization treatment is performed to obtain the first melt. The first melt is heated to 770℃~780℃, and a magnesium-zirconium master alloy is added. After melting, a second homogenization treatment is performed to obtain the second melt. The second melt is refined, slag is removed, and the temperature is maintained for 10-12 minutes to obtain the third melt; The third melt was cooled to 720℃~730℃ and allowed to stand for 10 minutes before being cast to obtain a magnesium alloy ingot.

[0034] When alloying magnesium alloy raw materials, pure magnesium is melted under the combined protection of a CO2 and SF6 mixed gas and a chloride flux. This protective system effectively isolates the magnesium from air, preventing oxidation and combustion of the molten magnesium at high temperatures and ensuring the purity of the melt. After the magnesium melt is heated to 740℃~750℃, magnesium-gadolinium master alloy, magnesium-yttrium master alloy, and pure zinc are added sequentially. This temperature range ensures rapid melting of these alloying elements while avoiding increased burn-off due to excessively high temperatures. After heating the first melt to 770℃~780℃, magnesium-zirconium master alloy is added. The higher temperature facilitates the full dissolution and absorption of the magnesium-zirconium master alloy, ensuring that zirconium exerts its grain-refining strengthening effect. After refining and slag removal, the melt is held at a temperature for 10~12 minutes to allow inclusions in the melt to float and be removed. Finally, the third melt is cooled to 720℃~730℃ and allowed to stand for 10 minutes before casting. A suitable casting temperature helps to obtain magnesium alloy ingots with uniform structure and few defects.

[0035] In some implementations, the raw materials, tools, and molds used are surface-cleaned and thoroughly baked before melting to minimize the introduction of impurities during the melting process.

[0036] In some implementations, the baking regime for the raw materials, tools, and molds is 150°C / 30 min; In some implementations, the volume ratio of CO2 to SF6 protective gas during the casting process is 99.9:0.1.

[0037] In some implementations, continuous CO2+SF6 gas protection is required during the melt casting process to reduce oxide inclusions in the ingot.

[0038] In some implementations, to ensure the safety of the casting process, the materials and crucible must be baked; to ensure the purity of the materials, an additional 0.5 to 1.0 kg of raw material is added before casting as a base material to be poured into the scrap mold; a feeding action must be performed at the end of the casting process to reduce internal defects in the alloy ingot and improve the quality of the ingot.

[0039] In some implementations, the purity of the pure magnesium is ≥99.95%; The purity of pure zinc is ≥99.995%; The rare earth element content in magnesium gadolinium master alloy, magnesium yttrium master alloy and magnesium zirconium master alloy is 29% to 31% by mass fraction.

[0040] The purity of pure magnesium is limited to ≥99.95%, the purity of pure zinc to ≥99.995%, and the rare earth element content in magnesium-gadolinium master alloy, magnesium-yttrium master alloy, and magnesium-zirconium master alloy is 29% to 31%. These high-purity raw materials and stable-composition master alloys can minimize the introduction of impurity elements, ensure precise control of alloy composition, and provide a basic guarantee for obtaining stable and excellent mechanical properties in subsequent heat treatment.

[0041] In some implementations, both the primary and secondary homogenization processes employ a combination of mechanical stirring and ultrasonic treatment. The frequency of ultrasonic treatment is 18kHz to 22kHz, and the treatment time is 3min to 5min per treatment.

[0042] Both the primary and secondary homogenization processes employ a combination of mechanical stirring and ultrasonic treatment. Mechanical stirring first disperses the alloying elements in the magnesium alloy melt, followed by ultrasonic treatment at a frequency of 18kHz–22kHz for 3–5 minutes. The cavitation and acoustic flow effects generated by ultrasound in the melt achieve a microscopically uniform distribution of the alloying elements, preventing component segregation and ensuring the homogeneity of the ingot structure. For example, the ultrasonic frequencies can be 18.5kHz, 19.0kHz, 19.5kHz, 20.0kHz, 20.5kHz, 21.0kHz, 21.2kHz, 21.5kHz, etc.; and the treatment times can be 3.2min, 3.4min, 3.6min, 3.8min, 4.0min, 4.2min, 4.4min, 4.6min, etc.

[0043] In some embodiments, solution treatment of magnesium alloy ingots to obtain a solution-treated magnesium alloy includes: At a heating rate of 14℃ / min to 16℃ / min, the magnesium alloy ingot is first heated to 420℃ to 440℃ and then held for 5min to 10min. At a heating rate of 4℃ / min to 6℃ / min, the magnesium alloy ingot after the first holding is heated to 460℃ to 480℃ for the second time and held for 6h to 8h. The magnesium alloy ingot after the second heat treatment is quenched to obtain a solid solution magnesium alloy.

[0044] When performing solution treatment on magnesium alloy ingots, a stepped heating method is adopted. First, the temperature is raised to 420℃–440℃ at a heating rate of 14℃ / min–16℃ / min and held for 5–10 minutes. This stage ensures uniform heating of the ingot and avoids thermal stress accumulation caused by excessively rapid heating. Subsequently, the temperature is raised to 460℃–480℃ at a heating rate of 4℃ / min–6℃ / min and held for 6–8 hours. The slower heating rate helps control the phase transformation process, ensuring the second phase fully dissolves and enters the matrix. Combined with optimized holding time, this shortens the treatment cycle while achieving complete solution treatment.

[0045] In some implementations, quenching is water quenching, and the water temperature for water quenching is 70℃~80℃.

[0046] After solution treatment, quenching is performed using hot water at 70℃~80℃. This temperature provides sufficient cooling to preserve the high-temperature supersaturated solid solution structure while avoiding excessive thermal stress and ingot cracking risks that may occur with cold water quenching. For example, the water temperature can be 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, etc.

[0047] In some embodiments, aging treatment is performed on the solution-treated magnesium alloy to obtain an aged magnesium alloy, including: At a heating rate of 14℃ / min to 16℃ / min, the solid solution magnesium alloy was heated to 170℃ to 190℃ for the third time and held at that temperature for 5 min to 10 min. At a heating rate of 4℃ / min to 6℃ / min, the solid solution magnesium alloy after the third holding was heated to 200℃ to 210℃ and held for 10h to 12h. The solid solution magnesium alloy after the fourth heat preservation was air-cooled to obtain the aged magnesium alloy.

[0048] The aging treatment of solution-treated magnesium alloys also employs a stepped heating method. First, the temperature is raised to 170℃–190℃ at a heating rate of 14℃ / min–16℃ / min and held for 5–10 minutes to ensure uniform furnace and workpiece temperatures. Subsequently, the temperature is raised to 200℃–210℃ at a heating rate of 4℃ / min–6℃ / min and held for 10–12 hours. This combination of aging temperature range and holding time promotes the uniform precipitation of nano-reinforcing phases and controls their size within an optimal range, resulting in significant precipitation strengthening.

[0049] In some implementations, the total treatment time for solution treatment and aging treatment is 16h to 22h.

[0050] The total processing time for solution treatment and aging treatment is controlled within the range of 16h to 22h. This time cycle is significantly shorter than that of traditional magnesium alloy heat treatment processes, reflecting the short-process characteristic of this solution. It significantly improves production efficiency while ensuring the strengthening effect of heat treatment. For example, the total processing time for solution treatment and aging treatment can be 16.5h, 17.0h, 17.5h, 18.0h, 18.5h, 19.0h, 19.5h, 20.0h, etc.

[0051] In some embodiments, the aged magnesium alloy meets the following properties: tensile strength ≥280MPa, yield strength ≥175MPa, and elongation ≥12%.

[0052] This application achieves excellent comprehensive mechanical properties of aged magnesium alloys with tensile strength ≥280MPa, yield strength ≥175MPa, and elongation ≥12% through the synergistic design of alloy composition and heat treatment process.

[0053] In the alloy composition design, Gd (6.51%–8.99%), Y (0.8%–1.0%), and Zr (0.3%–0.5%) are used as the base, with an appropriate amount of Zn added, satisfying 1 / 25 ≤ [Zn] / ([Gd]+[Y]+[Zr]) ≤ 1 / 16. Gd plays a role in solid solution plasticization and precipitation strengthening, providing the main source of strength for the alloy; Y inhibits the coarsening of Mg-Gd nano-precipitates at high temperatures, ensuring the stability of the precipitates; Zr improves plasticity through grain refinement; the appropriate addition of Zn lowers the solid solution temperature and shortens the solid solution time by reducing the melting point of the second phase, while promoting the precipitation of nano-reinforcing phases during aging, thus ensuring the strengthening effect while shortening the cycle.

[0054] In terms of heat treatment, a solution treatment at 460℃~480℃ for 6h~8h and an aging treatment at 200℃~210℃ for 10h~12h are employed, with a stepped heating method (e.g., holding at 430℃ / 180℃ followed by slow heating) to ensure uniform microstructure transformation. The solution treatment allows alloying elements to fully dissolve into the matrix, while quenching preserves the supersaturated solid solution. The aging treatment promotes the uniform precipitation of nano-reinforcing phases with a size of approximately 10nm. These fine and dispersed precipitates achieve significant precipitation strengthening by hindering dislocation movement, enabling the tensile strength and yield strength to reach the aforementioned levels.

[0055] The addition of Zn avoids the problem of sacrificing plasticity in pursuit of strength in traditional processes. By controlling the Zn content, excessive LPSO phase and acicular Zn-Zr-rich phase are avoided, while the strengthening effects of Gd, Y, and Zr are preserved. At the same time, optimized heat treatment parameters prevent grain coarsening and precipitate coarsening, enabling the alloy to maintain an elongation of ≥12% while achieving high strength, thus achieving a good balance between strength and ductility.

[0056] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0057] Example 1 Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 8.99%, Y 0.96%, Zn 0.41%, Zr 0.40%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 1 / 25.

[0058] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 750℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 780℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0059] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 min, then increased to 470°C at a rate of 5°C / min and held for 8 h. Finally, the alloy was quenched in hot water at 80°C to obtain the solution-treated magnesium alloy.

[0060] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180 °C at a rate of 15 °C / min and held for 8 min. Then, the temperature was increased to 210 °C at a rate of 5 °C / min and held for 10 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0061] Figure 2 This is a distribution diagram of nano-precipitated phases in an aged magnesium alloy matrix provided in Example 1 of this application; Figure 3 This is a morphology diagram of the nano-precipitated phase in the aged magnesium alloy matrix provided in Example 1 of this application.

[0062] Depend on Figure 2 and Figure 3 It can be seen that in the aged magnesium alloy prepared by the short-process heat treatment in Example 1, a large number of uniform and fine nano-reinforcements are distributed in the matrix. Figure 2 TEM images show that the nanoreinforcements are equiaxed and uniformly dispersed within the magnesium alloy matrix. Figure 3 High-magnification TEM images reveal that the nano-reinforcement is approximately 10 nm in size. The fine and dispersed nano-precipitates effectively hinder dislocation movement, resulting in a significant precipitation strengthening effect, thus enabling the aged magnesium alloy to possess both high strength and excellent ductility. This confirms that the appropriate addition of Zn and optimized solution and aging processes successfully promoted the uniform precipitation of the nano-reinforcement phase and effectively suppressed its coarsening.

[0063] Example 2 Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 8.51%, Y 0.90%, Zn 0.43%, Zr 0.36%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 0.044.

[0064] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 740℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 770℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0065] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.02 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 minutes. Then, the temperature was increased to 480°C at a rate of 5°C / min and held for 8 hours. Finally, the alloy was quenched in hot water at 70°C to obtain the solution-treated magnesium alloy.

[0066] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.02 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180 °C at a rate of 15 °C / min and held for 8 min. Then, the temperature was increased to 210 °C at a rate of 5 °C / min and held for 10 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0067] Mechanical properties: The aged magnesium alloy of this embodiment was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 315MPa, yield strength 198MPa, elongation 12.5%.

[0068] Example 3 Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 8.02%, Y 0.85%, Zn 0.40%, Zr 0.35%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 0.043.

[0069] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 745℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 775℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0070] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.02 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 min, then increased to 480°C at a rate of 5°C / min and held for 6 h. Finally, the alloy was quenched in hot water at 70°C to obtain the solution-treated magnesium alloy.

[0071] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.02 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180 °C at a rate of 15 °C / min and held for 8 min. Then, the temperature was increased to 200 °C at a rate of 5 °C / min and held for 12 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0072] Mechanical properties: The aged magnesium alloy of this embodiment was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 299MPa, yield strength 185MPa, elongation 13.6%.

[0073] Example 4 Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 6.55%, Y 0.81%, Zn 0.39%, Zr 0.40%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 0.05.

[0074] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 750℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 780℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0075] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 min, then increased to 460°C at a rate of 5°C / min and held for 8 h. Finally, the alloy was quenched in hot water at 80°C to obtain the solution-treated magnesium alloy.

[0076] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180°C at a rate of 15°C / min and held for 8 min. Then, the temperature was increased to 210°C at a rate of 5°C / min and held for 10 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0077] Mechanical properties: The aged magnesium alloy of this embodiment was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 281MPa, yield strength 177MPa, elongation 14.0%.

[0078] Example 5 Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 7.05%, Y 0.91%, Zn 0.40%, Zr 0.39%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 0.047.

[0079] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 750℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 780℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0080] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.02 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 min, then increased to 480°C at a rate of 5°C / min and held for 7 h. Finally, the alloy was quenched in hot water at 80°C to obtain the solution-treated magnesium alloy.

[0081] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.02 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180 °C at a rate of 15 °C / min and held for 8 min. Then, the temperature was increased to 210 °C at a rate of 5 °C / min and held for 10 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0082] Mechanical properties: The aged magnesium alloy of this embodiment was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 294MPa, yield strength 183MPa, elongation 13.8%.

[0083] Example 6 Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 7.49%, Y 0.91%, Zn 0.55%, Zr 0.42%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 0.061.

[0084] Alloy casting: Before smelting, weigh high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy and Mg-Zr master alloy according to the composition ratio, and bake the raw materials, operating tools and casting mold at 150℃ for 30 minutes.

[0085] High-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500°C, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced, and a chloride flux was applied. The temperature was further increased to 700°C to completely melt the magnesium ingot, yielding a magnesium melt. After the magnesium melt reached 750°C, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20 kHz for 5 minutes, yielding the first melt. The first melt was then heated to 770°C, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20 kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725°C and allowed to stand for 10 minutes before being poured. During the pouring process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0086] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 minutes. Then, the temperature was increased to 480°C at a rate of 5°C / min and held for 8 hours. Finally, the alloy was quenched in hot water at 70°C to obtain the solution-treated magnesium alloy.

[0087] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.02 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180 °C at a rate of 15 °C / min and held for 8 min. Then, the temperature was increased to 205 °C at a rate of 5 °C / min and held for 12 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0088] Mechanical properties: The aged magnesium alloy of this embodiment was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 301MPa, yield strength 189MPa, elongation 13.8%.

[0089] Example 7 Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 8.01%, Y 0.80%, Zn 0.56%, Zr 0.41%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 0.061.

[0090] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 750℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 780℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0091] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 min, then increased to 480°C at a rate of 5°C / min and held for 8 h. Finally, the alloy was quenched in hot water at 70°C to obtain the solution-treated magnesium alloy.

[0092] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180°C at a rate of 15°C / min and held for 8 min. Then, the temperature was increased to 210°C at a rate of 5°C / min and held for 10 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0093] Mechanical properties: The aged magnesium alloy of this embodiment was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 308MPa, yield strength 193MPa, elongation 13.3%.

[0094] Comparative Example 1 The difference between this comparative example and Example 1 is that in the alloy design composition, Zn / (Gd+Y+Zr) > 1 / 16.

[0095] Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 8.98%, Y 0.97%, Zn 1.01%, Zr 0.40%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio Zn / (Gd+Y+Zr) = 0.098, which is greater than 1 / 16 and does not meet the specified range of 1 / 25 ≤ Zn / (Gd+Y+Zr) ≤ 1 / 16.

[0096] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 750℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 780℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0097] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 min, then increased to 470°C at a rate of 5°C / min and held for 8 h. Finally, the alloy was quenched in hot water at 80°C to obtain the solution-treated magnesium alloy.

[0098] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180 °C at a rate of 15 °C / min and held for 8 min. Then, the temperature was increased to 210 °C at a rate of 5 °C / min and held for 10 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0099] Mechanical properties: The aged magnesium alloy of this comparative example was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 258MPa, yield strength 163MPa, elongation 8.4%.

[0100] Comparative Example 2 The difference between this comparative example and Example 1 is that the solution heat treatment temperature is >480℃ and the time is >8h. Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 8.95%, Y 0.98%, Zn 0.41%, Zr 0.40%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 0.04.

[0101] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 750℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 780℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0102] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430°C at a rate of 15°C / min and held for 8 min, then increased to 500°C at a rate of 5°C / min and held for 12 h. The alloy was then quenched in hot water at 80°C to obtain the solution-treated magnesium alloy. This solution treatment temperature (500°C) is higher than the defined range of 460°C–480°C, and the solution treatment time (12 h) is longer than the defined range of 6 h–8 h.

[0103] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180 °C at a rate of 15 °C / min and held for 8 min. Then, the temperature was increased to 210 °C at a rate of 5 °C / min and held for 10 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0104] Mechanical properties: The aged magnesium alloy of this comparative example was processed into bar-shaped tensile samples of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 283MPa, yield strength 180MPa, elongation 7.6%.

[0105] Comparative Example 3 The difference between this comparative example and Example 1 is that the aging heat treatment temperature is >210℃ and the time is >12h.

[0106] Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 8.96%, Y 0.95%, Zn 0.40%, Zr 0.41%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. The ratio of Zn / (Gd+Y+Zr) is 0.04.

[0107] Alloy casting: Before smelting, high-purity magnesium, pure zinc, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to the composition ratio. The raw materials, operating tools, and casting molds were baked at 150℃ for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500℃, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700℃ to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 750℃, Mg-Gd master alloy, Mg-Y master alloy, and pure zinc were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 5 minutes, obtaining the first melt. The first melt was heated to 780℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0108] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430℃ at a rate of 15℃ / min and held for 8 min, then increased to 500℃ at a rate of 5℃ / min and held for 12 h. Finally, the alloy was quenched in hot water at 80℃ to obtain the solution-treated magnesium alloy.

[0109] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180°C at a rate of 15°C / min and held for 8 min. Then, the temperature was increased to 230°C at a rate of 5°C / min and held for 24 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy. The aging temperature (230°C) is higher than the specified range of 200°C to 210°C, and the aging time (24 h) is longer than the specified range of 10 h to 12 h.

[0110] Mechanical properties: The aged magnesium alloy of this comparative example was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 239MPa, yield strength 141MPa, elongation 16.4%.

[0111] Comparative Example 4 The difference between this comparative example and Example 1 is that no Zn element was added.

[0112] Alloy composition: The chemical composition of the magnesium alloy ingot, by mass fraction, includes: Gd 8.98%, Y 0.95%, Zr 0.41%, with the total content of impurity elements not exceeding 0.1%, and the balance being Mg. No Zn element has been added to this composition.

[0113] Alloy casting: Before smelting, high-purity magnesium, Mg-Gd master alloy, Mg-Y master alloy, and Mg-Zr master alloy were weighed according to their composition ratios. The raw materials, tools, and casting molds were baked at 150°C for 30 minutes. The high-purity magnesium was placed in a crucible and then placed in a pit-type resistance furnace. When the furnace temperature reached 500°C, a mixture of CO2 and SF6 gas (volume ratio 99.9:0.1) was introduced and covered with chloride flux. The temperature was further increased to 700°C to completely melt the magnesium ingot, obtaining magnesium melt. After the magnesium melt was heated to 750°C, Mg-Gd master alloy and Mg-Y master alloy were added sequentially. After complete melting, a first homogenization treatment was performed. The first homogenization treatment was carried out by mechanical stirring combined with ultrasonic treatment at a frequency of 20 kHz for 5 minutes, obtaining the first melt. The first melt was heated to 780℃, and a Mg-Zr master alloy was added. After melting, a second homogenization treatment was performed using mechanical stirring combined with ultrasonic treatment at a frequency of 20kHz for 10 minutes, yielding the second melt. The second melt was then refined, slag was removed, and the temperature was maintained for 10 minutes to obtain the third melt. The third melt was cooled to 725℃ and allowed to stand for 10 minutes before casting. During the casting process, a mixture of CO2 and SF6 gas was continuously introduced for protection, resulting in a magnesium alloy ingot.

[0114] Alloy heat treatment: Solution treatment: Solution treatment was performed under argon protection. The magnesium alloy ingot was placed in a muffle furnace, evacuated to -0.1 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 430℃ at a rate of 15℃ / min and held for 8 min, then increased to 500℃ at a rate of 5℃ / min and held for 12 h. Finally, the alloy was quenched in hot water at 80℃ to obtain the solution-treated magnesium alloy.

[0115] Timeliness processing: Aging treatment was performed under argon protection. The solution-treated magnesium alloy was placed in a muffle furnace, evacuated to -0.08 MPa, and then purged with argon to bring the furnace pressure to 0.01 MPa. The evacuation and argon purging processes were repeated twice before heating. The temperature was increased to 180 °C at a rate of 15 °C / min and held for 8 min. Then, the temperature was increased to 230 °C at a rate of 5 °C / min and held for 24 h. The alloy was then removed and air-cooled to obtain the aged magnesium alloy.

[0116] Mechanical properties: The aged magnesium alloy of this comparative example was processed into a bar-shaped tensile sample of national standard size for testing. Its room temperature mechanical properties are as follows: tensile strength 235MPa, yield strength 137MPa, elongation 17.9%.

[0117] The magnesium alloy compositions of each embodiment and comparative example are summarized in Table 1, the heat treatment regimes are summarized in Table 2, and the mechanical properties are summarized in Table 3.

[0118] Table 1. Chemical composition (wt.%) of magnesium alloys in each embodiment and comparative example.

[0119] Table 2 Heat treatment regimes for magnesium alloys in each embodiment and comparative example.

[0120] Table 3 Mechanical properties of magnesium alloys in each embodiment and comparative example

[0121] As shown in Examples 1 to 7 of Tables 1 and 3, when the chemical composition of the magnesium alloy ingot meets the requirements of Gd 6.51% to 8.99%, Y 0.8% to 1.0%, Zr 0.3% to 0.5%, and impurity elements ≤ 0.1%, and an appropriate amount of Zn is added, and the Zn / (Gd+Y+Zr) ratio is controlled within the range of 1 / 25 to 1 / 16, the obtained aged magnesium alloy exhibits excellent comprehensive mechanical properties when combined with the solution treatment (holding temperature 460℃ to 480℃, holding time 6h to 8h) and aging treatment (holding temperature 200℃ to 210℃, holding time 10h to 12h) shown in Table 2. The tensile strength reaches 281MPa to 318MPa, the yield strength reaches 177MPa to 198MPa, and the elongation reaches 12.5% ​​to 14.0%. This indicates that within the composition range and heat treatment parameters defined in this application, the alloy can fully utilize the solid solution plasticizing and precipitation strengthening effects of Gd, the stabilizing effect of Y on the precipitated phase, the grain refining strengthening effect of Zr, and the synergistic effect of Zn in lowering the solid solution temperature and promoting aging precipitation, thereby achieving a good match between high strength and high plasticity while significantly shortening the heat treatment process.

[0122] A comparison between Comparative Example 1 and Example 1 shows that when the Zn addition is too high, causing the Zn / (Gd+Y+Zr) ratio (0.098) to exceed the upper limit of 1 / 16 specified in this application, even with the same heat treatment process, the tensile strength of the aged magnesium alloy decreases to 258 MPa and the elongation decreases to 8.4%, with both strength and plasticity significantly deteriorating. This indicates that excessive Zn will form too many LPSO phases and acicular Zn-rich Zr phases in the matrix, consuming strengthening elements such as Gd, Y, and Zr and weakening their strengthening effect.

[0123] A comparison of Comparative Example 2 and Example 1 shows that when the solution treatment temperature (500°C) is higher than the upper limit of 480°C specified in this application, and the solution treatment time (12h) is longer than the upper limit of 8h specified in this application, the elongation of the aged magnesium alloy decreases to 7.6%, and the plasticity decreases significantly. This indicates that excessively high solution temperatures and excessively long solution times lead to the formation of more acicular Zn-Zr phases in the matrix, deteriorating the ductility of the alloy.

[0124] A comparison of Comparative Example 3 and Example 1 shows that when the aging treatment temperature (230°C) is higher than the upper limit of 210°C specified in this application, and the aging time (24h) is longer than the upper limit of 12h specified in this application, the tensile strength of the aged magnesium alloy decreases to 239 MPa and the yield strength decreases to 141 MPa, indicating a significant reduction in strength. This suggests that excessively high aging temperatures and excessively long aging times can lead to coarsening of the nano-reinforcement, weakening the precipitation strengthening effect.

[0125] A comparison between Comparative Example 4 and Example 1 shows that when no Zn element is added to the alloy, the tensile strength of the aged magnesium alloy is only 235 MPa and the yield strength is only 137 MPa, which is significantly lower than that of the examples. This indicates that the appropriate addition of Zn element plays a key role in reducing the solution temperature, shortening the solution time, and promoting the precipitation of nano-reinforcing phases during the aging process.

[0126] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: (1) A good balance between high strength and excellent ductility has been achieved. This application utilizes the solid solution plasticizing and precipitation strengthening effects of Gd, the inhibition of high-temperature coarsening of Mg-Gd nano-precipitates by Y, the improvement of plasticity by Zr through grain refinement, and the appropriate addition of Zn to achieve significant precipitation strengthening while retaining good plastic deformation capacity. The final aged magnesium alloy has a tensile strength of over 280 MPa and an elongation of over 12%, overcoming the technical bottleneck of traditional cast magnesium alloys where strength and ductility are difficult to achieve simultaneously.

[0127] (2) The heat treatment process is significantly shortened. This application utilizes the property of Zn element to lower the melting point of the second phase, reducing the solution treatment temperature to 460℃~480℃ and the holding time to 6h~8h; at the same time, it utilizes the effect of Zn element in promoting the precipitation of nano-reinforcing phase during aging, controlling the aging treatment temperature to 200℃~210℃ and the holding time to 10h~12h. The entire heat treatment process can be controlled within the range of 16h~22h, which is significantly shortened compared to the traditional magnesium alloy heat treatment process (which usually requires tens of hours), significantly reducing time costs and energy consumption.

[0128] (3) Improved production efficiency and reduced manufacturing costs. Due to the shortened heat treatment process, the utilization rate and turnover rate of production equipment are greatly improved, and the overall manufacturing cost is significantly reduced. This is especially important for price and efficiency-sensitive application areas (such as new energy vehicles, low-altitude economy, robots, etc.), laying an economic foundation for the large-scale industrial application of this process.

[0129] (4) Improved component dimensional accuracy and surface quality. Shortening the high-temperature treatment time effectively reduced the deformation of magnesium alloy components during heat treatment, lowered internal stress, and controlled the oxide layer thickness. The resulting aged magnesium alloy has higher dimensional accuracy and better surface quality, reducing subsequent machining allowances and further meeting the needs of precision manufacturing of parts.

[0130] (5) A fine and uniform nano-reinforcement structure was obtained. By regulating the Zn element and optimizing the aging treatment parameters, a large number of fine and dispersed nano-reinforcement phases (about 10 nm in size) were precipitated in the magnesium alloy matrix. This uniformly distributed nano-precipitation structure is the microstructure basis for achieving a good match between high strength and good plasticity of the material.

[0131] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A short-process heat treatment process for magnesium alloys, characterized in that, The process includes: Magnesium alloy raw materials are alloyed and cast to obtain magnesium alloy ingots; the chemical composition of the magnesium alloy ingots, by mass fraction, includes: Gd: 6.51%~8.99%, Y: 0.8%~1.0%, Zr: 0.3%~0.5%, impurity elements ≤0.1%, Mg, Zn; The magnesium alloy ingot is subjected to solution treatment to obtain a solution-treated magnesium alloy; the holding temperature of the solution treatment is 460℃~480℃, and the holding time is 6h~8h. The solid solution magnesium alloy is subjected to aging treatment to obtain an aged magnesium alloy; the aging treatment temperature is 200℃~210℃ and the time is 10~12h.

2. The process according to claim 1, characterized in that, The chemical components satisfy the following relationship: 1 / 25 ≤ [Zn] / ([Gd]+[Y]+[Zr]) ≤ 1 / 16 In the formula, [Zn] represents the mass fraction of Zn, [Gd] represents the mass fraction of Gd, [Y] represents the mass fraction of Y, and [Zr] represents the mass fraction of Zr.

3. The process according to claim 1, characterized in that, The process of alloy melting and casting magnesium alloy raw materials to obtain magnesium alloy ingots includes: Pure magnesium is melted under the combined protection of a mixture of CO2 and SF6 gas and a chloride flux to obtain magnesium melt; After the magnesium melt is heated to 740℃~750℃, magnesium gadolinium master alloy, magnesium yttrium master alloy and pure zinc are added in sequence. After all the magnesium melts, a homogenization treatment is performed to obtain the first melt. The first melt is heated to 770℃~780℃, and a magnesium-zirconium master alloy is added. After melting, a second homogenization treatment is performed to obtain the second melt. The second melt is refined, slag is removed, and the temperature is maintained for 10-12 minutes to obtain the third melt; The third melt is cooled to 720℃~730℃ and allowed to stand for 10 minutes before being cast to obtain a magnesium alloy ingot.

4. The process according to claim 3, characterized in that, The purity of the magnesium is ≥99.95%; The purity of the zinc is ≥99.995%; The rare earth element content in the magnesium-gadolinium master alloy, the magnesium-yttrium master alloy, and the magnesium-zirconium master alloy is 29% to 31% by mass fraction.

5. The process according to claim 3, characterized in that, Both the primary homogenization process and the secondary homogenization process employ a combination of mechanical stirring and ultrasonic treatment. The frequency of the ultrasonic treatment is 18kHz to 22kHz, and the treatment time is 3min to 5min per treatment.

6. The process according to claim 1, characterized in that, The step of solution treatment of the magnesium alloy ingot to obtain a solution-treated magnesium alloy includes: The magnesium alloy ingot is heated to 420℃ to 440℃ at a heating rate of 14℃ / min to 16℃ / min, and held at that temperature for 5min to 10min. At a heating rate of 4℃ / min to 6℃ / min, the magnesium alloy ingot, after the first heat preservation, is heated to 460℃ to 480℃ for the second time and held for 6h to 8h. The magnesium alloy ingot after the second heat treatment is quenched to obtain a solid solution magnesium alloy.

7. The process according to claim 6, characterized in that, The quenching is water quenching, and the water temperature for water quenching is 70℃~80℃.

8. The process according to claim 1, characterized in that, The step of aging the solution-treated magnesium alloy to obtain an aged magnesium alloy includes: The solid solution magnesium alloy was heated to 170℃ to 190℃ at a heating rate of 14℃ / min to 16℃ / min, and then held at that temperature for 5min to 10min. At a heating rate of 4℃ / min to 6℃ / min, the solid solution magnesium alloy after the third holding is heated to 200℃ to 210℃ for the fourth time and held for 10h to 12h. The solid solution magnesium alloy after the fourth heat preservation was air-cooled to obtain an aged magnesium alloy.

9. The process according to claim 1, characterized in that, The total processing time for the solution treatment and the aging treatment is 16h to 22h.

10. The process according to claim 1, characterized in that, The aged magnesium alloy meets the following properties: tensile strength ≥280MPa, yield strength ≥175MPa, elongation ≥12%.

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