Micro-alloyed fast-extrusion flame-retardant magnesium alloy and preparation method thereof

Abstract

The invention discloses a micro-alloying rapid extrusion flame-retardant magnesium alloy and a preparation method thereof, and belongs to the technical field of metal materials. The microalloying fast extrusion flame-retardant magnesium alloy is prepared from the following components in percentage by mass: 1.0 to 1.8 percent of aluminum, 0.3 to 0.4 percent of calcium, 0.4 to 0.6 percent of manganese, 0 to 0.08 percent of nano particles, less than or equal to 0.02 percent of inevitable impurities and the balance of magnesium. Calcium is preferentially oxidized at high temperature to form a compact CaO layer to block oxygen, so that the ignition point of the alloy is obviously improved; a high-density nanophase is dynamically separated out from aluminum and manganese in the rapid extrusion process, the grain boundary is effectively pinned, grain coarsening is inhibited, and the stability of a microstructure below an oxidation film is enhanced; nanoparticles are combined with ultrasonic melt treatment to refine the structure, surface oxidation film microdefects are filled at the same time, and the self-repairing capacity and compactness are improved. According to the design, through microalloying design (the total element content is smaller than or equal to 2.8%), nanoparticle reinforcement and a rapid extrusion process are cooperated, collaborative optimization of low production cost, good flame retardant property and efficient extrusion capacity of the alloy is achieved, and the industrial prospect is wide.

Description

Technical Field

[0001] This invention belongs to the field of metal materials technology, specifically relating to a micro-alloyed rapid extrusion flame-retardant magnesium alloy and its preparation method. Background Technology

[0002] Magnesium alloys exhibit significant advantages in engineering materials due to their low density, high specific strength and specific stiffness, as well as excellent damping and electromagnetic shielding properties. Among existing commercially available magnesium alloy products, magnesium-aluminum alloys still dominate, with alloys such as AZ91, AZ31, and AZ80 being the most widely used magnesium alloy series due to their cost advantages and room-temperature mechanical properties. However, these magnesium alloys typically have coarse grains in their as-cast structure and are prone to casting defects such as porosity and shrinkage cavities. They are also susceptible to cracking during high-speed extrusion, usually requiring a reduction in extrusion rate to ensure formability. This results in low extrusion efficiency, high energy consumption, and high processing costs, all of which collectively limit their application as primary load-bearing structural materials.

[0003] With the rapid development of new energy vehicle technology, especially the increasing safety requirements for key components such as battery packs and electric drive systems, the flame retardant properties of materials have become a core indicator for ensuring vehicle safety and reliability. Currently, key components of new energy vehicles require materials with higher flame retardant ratings and longer thermal runaway delay times, making the improvement of the flame retardant properties of magnesium alloys a key research focus in the industry. However, the application of traditional commercial magnesium-aluminum alloys is severely limited due to their low ignition point and susceptibility to oxidation and combustion at high temperatures, particularly in critical components such as battery packs where safety requirements are extremely high.

[0004] Therefore, developing a novel magnesium alloy material that combines low production cost, good flame retardancy, and efficient extrusion capability has become a key technical challenge that urgently needs to be addressed by those skilled in the art. A breakthrough in this technology is expected to expand the application range of magnesium alloys in multiple fields and further promote the development of lightweight design and energy conservation and emission reduction. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a microalloyed rapid extrusion flame-retardant magnesium alloy and its preparation method. This invention achieves a balance between low cost, high flame retardancy and high formability of magnesium alloy by combining microalloying design, nanoparticle reinforcement, ultrasonic melt treatment preparation process and rapid extrusion process without adding rare earth elements. It is suitable for fields with high requirements for safety and lightweighting, such as new energy vehicle battery packs and aerospace.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a microalloyed, rapidly extruded, flame-retardant magnesium alloy, composed of the following components by mass percentage: aluminum 1.0-1.8%, calcium 0.3-0.4%, manganese 0.4-0.6%, nanoparticles 0-0.08%, unavoidable impurities ≤0.02%, and the balance being magnesium.

[0007] Preferably, the nanoparticles include titanium carbide nanoparticles and / or titanium diboride nanoparticles. In this invention, the nanoparticles serve as heterogeneous nucleation cores, significantly refining the microstructure; ultrasonic melt treatment ensures uniform dispersion of the nanoparticles in the melt, improving nucleation efficiency; simultaneously, at high temperatures, they migrate to the surface oxide layer to fill microscopic defects, effectively blocking oxygen.

[0008] Preferably, the alloying element content of the microalloyed rapid extrusion flame-retardant magnesium alloy is ≤2.8%, belonging to a low-alloy system. The alloy prepared by this invention avoids the increase of brittle phases caused by excessive alloying elements, which is beneficial for rapid extrusion.

[0009] This invention also provides a method for preparing microalloyed rapid extrusion flame-retardant magnesium alloys, comprising the following steps: S1. Weigh the raw materials according to the stated mass percentage of the components; Among them, magnesium, aluminum, calcium, manganese and nanoparticles are derived from pure magnesium, pure aluminum, magnesium-calcium master alloy, magnesium-manganese master alloy, titanium carbide / aluminum master alloy, and titanium diboride / aluminum master alloy. S2. After melting pure magnesium, add pure aluminum, magnesium-calcium master alloy and magnesium-manganese master alloy until completely melted, then clean the slag and stir. After heat preservation, blow in high-purity argon gas to refine and clean the slag. After heating again, add titanium carbide / aluminum master alloy and / or titanium diboride / aluminum master alloy. After they are completely melted, perform ultrasonic treatment on the melt and clean the slag again to obtain low-alloy magnesium alloy melt. S3. Obtain a microalloyed magnesium alloy ingot by pouring the microalloyed magnesium alloy melt into a steel mold; S4. After homogenization treatment, the microalloyed magnesium alloy ingot is extruded and deformed and then air-cooled to room temperature to obtain a microalloyed high-speed extruded flame-retardant magnesium alloy.

[0010] Preferably, the magnesium-calcium master alloy in S1 is Mg-20Ca, and the magnesium-manganese master alloy is Mg-3Mn.

[0011] Preferably, the titanium carbide / aluminum master alloy in S1 is Al-5Ti-0.2C and / or the titanium diboride / aluminum master alloy is Al-5Ti-1B. The addition of these alloys allows for the in-situ formation of titanium carbide nanoparticles and / or titanium diboride nanoparticles during the smelting process.

[0012] Preferably, the pure magnesium melting step in S2 is as follows: pure magnesium is placed in an iron crucible and then placed in a melting furnace, heated to 300-350℃ and held for 30-40 minutes to keep the raw material and the inside of the furnace dry, then heated to 450-500℃ and held for 50-60 minutes to preheat the raw material, and then heated to 680-720℃ and held to melt the pure magnesium.

[0013] Preferably, the heat preservation time in S2 is 5-10 minutes.

[0014] Preferably, the stable temperature for the second heating in step S2 is 680-720℃.

[0015] Preferably, the parameters for the ultrasonic treatment of the melt in S2 are: immersion depth in the melt 30mm, ultrasonic power 1200W, and ultrasonic time 120s; uniformly disperse the nanoparticles formed in situ, and at the same time effectively break dendrites and refine grains by utilizing the acoustic flow and cavitation effects of power ultrasound.

[0016] Preferably, the entire melting process in S2 is carried out under a protective atmosphere of carbon dioxide and sulfur hexafluoride; the volume ratio of carbon dioxide to sulfur hexafluoride is (90-99):(10-1).

[0017] Preferably, the homogenization process in S4 specifically involves: performing a three-stage step homogenization process (330℃ / 4h + 450℃ / 3h + 480℃ / 1h) on the microalloyed magnesium alloy ingot in a muffle furnace, followed by water quenching.

[0018] Preferably, the extrusion deformation process in S4 is as follows: before extrusion deformation, the microalloyed magnesium alloy ingot is preheated at 300-400℃ for 60-120 min, and the extrusion die is preheated at 300-400℃; the extrusion ratio is (10-70):1, and the extrusion exit rate is 5-30 m / min.

[0019] It contains at least the following beneficial technical effects: This invention successfully developed a micro-alloyed, rapidly extruded flame-retardant magnesium alloy through optimized alloy composition design and synergistic control of the preparation process. This alloy employs a low-alloying design, with a total alloy element content ≤2.8%, and contains no rare earth elements, significantly reducing production costs. Regarding flame-retardant properties, at high temperatures, calcium preferentially oxidizes on the alloy surface to form a dense CaO modified layer, effectively blocking oxygen diffusion and significantly increasing the ignition point. The addition of aluminum and manganese helps form a highly thermally stable dispersed nanophase, which effectively pins grain boundaries during rapid extrusion, inhibits grain growth, enhances the stability of the microstructure beneath the oxide film, and provides a rapid diffusion channel for elements, enabling the alloy to rapidly form a continuous and complete protective oxide film when exposed to high temperatures.

[0020] During the preparation process, the in-situ generation and uniform dispersion of nanoparticles were achieved by introducing trace amounts of titanium carbide nanoparticles and / or titanium diboride nanoparticles combined with ultrasonic melt treatment. The microstructure was further refined through the heterogeneous nucleation of the nanoparticles and the cavitation effect of high-power ultrasound. Simultaneously, the nanoparticles could effectively fill defects in the surface oxide film at high temperatures, enhancing its self-healing ability and density. A three-stage step homogenization heat treatment was employed to eliminate low-melting-point phases and ensure that high-melting-point phases were uniformly distributed in the matrix, providing a uniform and fine microstructure foundation for subsequent extrusion deformation. This alloy can be extruded at an exit rate of 5-30 m / min within a temperature range of 300-400℃, achieving high production efficiency. Simultaneously, the flame retardant point of the alloy was increased to above 825℃, significantly improving safety in use.

[0021] In summary, this invention, through a systematic combination of microalloying design, nanoparticle reinforcement, ultrasonic melt processing, and rapid extrusion, simultaneously achieves low-cost manufacturing, excellent flame-retardant properties, and efficient forming capabilities under low alloy content conditions. This meets the stringent fire safety requirements of applications such as battery pack shells for new energy vehicles and internal components for aerospace cabins, and has broad prospects for industrialization. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0028] Unless otherwise specified, all raw materials or instruments used in the following embodiments of the present invention are commercially available.

[0029] Titanium carbide / aluminum master alloy (Al-5Ti-0.2C, wt.%) Titanium diboride / aluminum master alloy (Al-5Ti-1B, wt.%); Magnesium-calcium master alloy (Mg-20Ca, wt.%); Magnesium-manganese master alloy (Mg-3Mn, wt.%).

[0030] Example 1 (1) Taking the Mg-1.0Al-0.4Ca-0.5Mn-0.02TiC alloy combined with ultrasonic melt treatment process as an example (composed of the following components by mass percentage: aluminum: 1.0%, calcium: 0.4%, manganese: 0.5%, titanium carbide nanoparticles: 0.02%, unavoidable impurities ≤0.02%, balance magnesium), its preparation method includes the following steps: According to the alloy composition ratio, pure magnesium, pure aluminum, magnesium-calcium master alloy, magnesium-manganese master alloy and titanium carbide / aluminum master alloy were selected as raw materials.

[0031] Pure magnesium is placed in an iron crucible and then placed in a melting furnace. It is heated to 350°C and held for 30 minutes to keep the raw materials and the inside of the furnace dry. Then, the temperature is raised to 450°C and held for 60 minutes to preheat the raw materials. Next, the temperature is raised to 680°C and held until the pure magnesium melts. Pure aluminum, magnesium-calcium master alloy, and magnesium-manganese master alloy are added until they are completely melted. Slag is removed and the mixture is stirred. After holding for 5-10 minutes, high-purity argon gas is blown in for refining and slag removal. The temperature is raised to 680°C again and titanium carbide / aluminum master alloy is added. After it is completely melted, ultrasonic melt treatment is performed with preset parameters (immersion depth 30 mm, ultrasonic power 1200 W, ultrasonic time 120 s). Then, slag is removed again to obtain low-alloy magnesium alloy melt. The entire melting process is carried out under a protective atmosphere of mixed carbon dioxide and sulfur hexafluoride, with a volume ratio of 90:10 between carbon dioxide and sulfur hexafluoride. The low-alloy magnesium alloy melt can be solidified and cast into a cylindrical ingot by pouring it into a steel mold. (2) The microalloyed Mg-1.0Al-0.4Ca-0.6Mn-0.02TiC magnesium alloy melt obtained in step (1) is poured into a steel mold at 200℃ by gravity casting to obtain a microalloyed magnesium alloy ingot. (3) The microalloyed Mg-1.0Al-0.4Ca-0.6Mn-0.02TiC magnesium alloy ingot obtained in step (2) is subjected to a three-stage homogenization treatment of 330℃ / 4h+450℃ / 3h+480℃ / 1h in a muffle furnace and then water quenched. (4) The homogenized heat-treated microalloyed Mg-1.0Al-0.4Ca-0.6Mn-0.02TiC magnesium alloy ingot obtained in step (3) is preheated at 400℃ for 30 min, and the extrusion die is preheated at 400℃. After extrusion deformation treatment with an extrusion ratio of 35:1 and an extrusion exit rate of 5 m / min, it is air-cooled to room temperature to obtain microalloyed fast extrusion flame-retardant magnesium alloy. The alloy is an extruded profile with an ignition point of 826℃.

[0032] Example 2 Taking the Mg-1.8Al-0.4Ca-0.5Mn-0.04TiC alloy combined with ultrasonic melt treatment as an example (composed of the following components by mass percentage: aluminum: 1.8%, calcium: 0.4%, manganese: 0.5%, titanium carbide nanoparticles: 0.04%, unavoidable impurities ≤0.02%, balance magnesium), its preparation method includes the following steps: According to the alloy composition ratio, pure magnesium, pure aluminum, magnesium-calcium master alloy, magnesium-manganese master alloy and titanium carbide / aluminum master alloy were selected as raw materials.

[0033] Pure magnesium is placed in an iron crucible and then placed in a melting furnace. It is heated to 300℃ and held for 30 minutes to keep the raw materials and the inside of the furnace dry. Then, the temperature is raised to 450℃ and held for 60 minutes to preheat the raw materials. Next, the temperature is raised to 680℃ and held until the pure magnesium melts. Pure aluminum, magnesium-calcium master alloy, and magnesium-manganese master alloy are added until they are completely melted. Slag is removed and the mixture is stirred. After holding for 5-10 minutes, high-purity argon gas is blown in for refining and slag removal. The temperature is raised to 680℃ again and titanium carbide / aluminum master alloy is added. After it is completely melted, ultrasonic melt treatment is performed with preset parameters (immersion depth 30mm, ultrasonic power 1200W, ultrasonic time 120s). Then, slag is removed again to obtain low-alloy magnesium alloy melt. The entire melting process is carried out under a protective atmosphere of mixed carbon dioxide and sulfur hexafluoride, with a volume ratio of 90:10 between carbon dioxide and sulfur hexafluoride. The low-alloy magnesium alloy melt can be solidified and cast into a cylindrical ingot by pouring it into a steel mold. (2) The microalloyed Mg-1.8Al-0.4Ca-0.5Mn-0.04TiC magnesium alloy melt obtained in step (1) is poured into a steel mold at 150℃ by gravity casting to obtain a microalloyed magnesium alloy ingot. (3) The microalloyed Mg-1.8Al-0.4Ca-0.5Mn-0.04TiC magnesium alloy ingot obtained in step (2) is subjected to a three-stage homogenization treatment of 330℃ / 4h+450℃ / 3h+480℃ / 1h in a muffle furnace, followed by water quenching.

[0034] (4) The homogenized heat-treated microalloyed Mg-1.8Al-0.4Ca-0.5Mn-0.04TiC magnesium alloy ingot obtained in step (3) is preheated at 400℃ for 30 min, and the extrusion die is preheated at 400℃. Then, after extrusion deformation treatment with an extrusion ratio of 30:1 and an extrusion exit rate of 5 m / min, it is air-cooled to room temperature to obtain microalloyed high-speed extruded flame-retardant magnesium alloy. The alloy is an extruded profile with an ignition point of 837℃.

[0035] Example 3 Taking the Mg-1.3Al-0.3Ca-0.4Mn-0.08TiB2 alloy combined with ultrasonic melt treatment as an example (composed of the following components by mass percentage: aluminum: 1.3%, calcium: 0.3%, manganese: 0.4%, titanium diboride nanoparticles: 0.08%, unavoidable impurities ≤0.02%, balance magnesium), its preparation method includes the following steps: According to the alloy composition ratio, pure magnesium, pure aluminum, magnesium-calcium master alloy, magnesium-manganese master alloy and titanium diboride / aluminum master alloy were selected as raw materials.

[0036] Pure magnesium was placed in an iron crucible and then placed in a melting furnace. It was heated to 350°C and held for 30 minutes to keep the raw materials and the inside of the furnace dry. Then, the temperature was raised to 500°C and held for 60 minutes to preheat the raw materials. Next, the temperature was raised to 720°C and held until the pure magnesium melted. Then, pure aluminum, magnesium-calcium master alloy and magnesium-manganese master alloy were added until they were completely melted. After slag removal and stirring, the temperature was held for 10 minutes and then high-purity argon gas was blown in for refining and slag removal. The temperature was raised to 720°C again and titanium diboride / aluminum master alloy was added. After it was completely melted, ultrasonic melt treatment with preset parameters was performed (immersion depth 30 mm, ultrasonic power 1200 W, ultrasonic time 120 s). Then, slag was removed again to obtain low-alloy magnesium alloy melt. The entire melting process is carried out under a protective atmosphere of mixed carbon dioxide and sulfur hexafluoride, with a volume ratio of 99:1 between carbon dioxide and sulfur hexafluoride. The low-alloy magnesium alloy melt can be solidified and cast into a cylindrical ingot by pouring it into a steel mold. (2) The microalloyed Mg-1.3Al-0.3Ca-0.4Mn-0.08TiB2 magnesium alloy melt obtained in step (1) is poured into a steel mold at 250°C by gravity casting to obtain a microalloyed magnesium alloy ingot. (3) The microalloyed Mg-1.3Al-0.3Ca-0.4Mn-0.08TiB2 magnesium alloy ingot obtained in step (2) is subjected to a three-stage homogenization treatment of 330℃ / 4h+450℃ / 3h+480℃ / 1h in a muffle furnace and then water quenched.

[0037] (4) The homogenized heat-treated microalloyed Mg-1.3Al-0.3Ca-0.4Mn-0.08TiB2 magnesium alloy ingot obtained in step (3) is preheated at 400℃ for 30 min, and the extrusion die is preheated at 400℃. Then, after extrusion deformation treatment with an extrusion ratio of 35:1 and an extrusion exit rate of 5 m / min, it is air-cooled to room temperature to obtain microalloyed high-speed extruded flame-retardant magnesium alloy. The alloy is an extruded profile with an ignition point of 841℃.

[0038] Comparative Example 1 The preparation method of Comparative Example 1 is the same as that of the Example, except that no titanium carbide / aluminum master alloy is added and no ultrasonic melt treatment is performed; the ignition point was tested to be 706°C.

[0039] Comparative Example 2 The preparation method of Comparative Example 2 is the same as that of the Example, except that no titanium carbide / aluminum master alloy is added and ultrasonic melt treatment is performed; the ignition point was tested to be 732°C.

[0040] Comparative Example 3 The preparation method of Comparative Example 3 is the same as that of the Example, except that a titanium carbide / aluminum master alloy is added and ultrasonic melt treatment is not performed; the ignition point is tested to be 751°C.

[0041] Comparative Example 4 The preparation method is based on the invention patent CN 114934218 A ("A Microalloyed High-Strength, Plastic, and Flame-Retardant Magnesium Alloy and Its Preparation Method"). The selected Mg-Al-Ca-Gd-Zr microalloyed high-strength, plastic, and flame-retardant magnesium alloy, by mass percentage, is: Al: 2.0 wt.%, Ca: 2.5 wt.%, Gd: 1.0 wt.%, Zr: 0.4 wt.%; the total amount of impurity elements Fe, Cu, and Ni is less than 0.02%. wt.%; the remainder is Mg. The preparation process includes the following steps: melting industrial pure magnesium ingots at 720℃, stirring, and removing slag; adding intermediate alloy while stirring and heating to 750℃, stirring for 13 minutes after the raw materials melt, and letting stand for 5 minutes; after the slag in the melt floats to the surface and the melt cools to 735℃, adding industrial pure aluminum ingots, stirring for 13 minutes, removing slag from the alloy melt, and letting stand for 13 minutes; after the melt cools to 690℃, removing slag again, and then performing semi-continuous casting; semi-continuous... The ingot was subjected to a three-stage homogenization process: holding it at 400℃ for 8 hours, then at 450℃ for 4 hours, and finally at 500℃ for 12 hours to obtain an alloy billet. Triaxial forging was then performed at 500℃ to refine the grains, further homogenize the microstructure, and eliminate casting defects. Extrusion deformation was then carried out at 330℃ with an extrusion ratio of 25 to obtain a magnesium alloy profile. The profile was then held at 180℃ for 24 hours and water-quenched in 65℃ water. The resulting microalloyed high-strength, ductile, flame-retardant magnesium alloy had an ignition point of 802℃.

[0042] Comparative Example 5 Referring to application publication number: CN 110423928 B (an invention patent for "a high-strength flame-retardant magnesium alloy"), the selected Mg-Sn-Bi-Ca-Nb-Sb-Nd-Sm high-strength flame-retardant magnesium alloy, by mass percentage, is: Sn: 2.4 wt.%, Bi: 1.5 wt.%, Ca: 0.6 wt.%, Nb: 0.5 wt.%, Sb: 0.45 wt.%; Nd: 3.5 wt.%; Sm: 1.5 wt.%; the total amount of Fe, Cu, and Ni among impurity elements is less than 0.2 wt.%; the remainder is Mg. The preparation process includes the following steps in 200... The raw materials were preheated at ℃; the pure metal raw materials were melted under a mixed protective atmosphere of CO2 and SF6 to obtain a pre-melted liquid at 700℃; intermediate alloy raw materials were added to the pre-melted liquid and held at 710℃ for 5 minutes. After all the intermediate alloys melted, the surface slag was removed, and the temperature was raised to 730℃ and held for 8 minutes to obtain a molten liquid; the temperature was lowered to 680℃ and poured to obtain a cast alloy; the cast alloy was held at 505℃ for 12 hours and then at 220℃ for 12 hours for solution aging treatment to obtain a high-strength flame-retardant magnesium alloy; Φ15mm × A 5mm cylindrical sample was placed in a resistance furnace at 450℃ for ignition point testing. The furnace temperature was raised at a rate of 5℃ / min, and a curve showing the surface temperature versus heating time was obtained. When the curve showed an inflection point, the magnesium alloy sample produced white smoke, indicating combustion. The temperature corresponding to this inflection point is the ignition point of the magnesium alloy. The obtained high-strength flame-retardant magnesium alloy had an ignition point of 793℃.

[0043] Comparative Example 6 The referenced journal is "Journal of Magnesium and Alloys", year: 2025, volume: 13, issue: 7, article pages: 3020-3036, authors: Longbiao Feng et al., title: "Effect of Y on oxidefilm formation and ignition behavior of magnesium-rare earth alloy". Table 1 on page 3021 shows the selected EV32-3Y magnesium alloy, by mass percentage: Nd: 3.14 wt.%; Gd: 2.12 wt.%; Zr: 0.23 wt.%; Zn: 0.21 wt.%; Y: 2.81 wt.%; balance Mg. The specific process was as follows: the raw materials were melted and cast at 800℃ under CO2 / SF6 (purity 40:60) protection. The alloy was cut into small cubes with length, width, and height of 10 mm, and then the samples were polished using 400-grit and 2000-grit sandpaper. Subsequently, the samples were placed in a resistance furnace for oxidation and combustion tests. A type K thermocouple, equipped with a digital converter and corresponding software (MAXCH4, accuracy 0.1℃), was used to measure the ignition temperature of the alloy. Figure 5 on page 3025: The obtained EV32-3Y magnesium alloy has an ignition point of 813.9℃.

[0044] Comparative Examples 1-3 demonstrate that adding titanium carbide / aluminum master alloy or not performing ultrasonic melt treatment both lower the ignition point of magnesium alloys; there is a synergistic effect between the two, and the decrease in ignition point is more significant when neither of the above two steps is performed simultaneously.

[0045] The microalloyed rapid extrusion flame-retardant magnesium alloy of the present invention adopts a low alloying design with a total alloy content of ≤2.8%. Through a simple composition system (containing only three microalloying elements and trace amounts of nanoparticles), it significantly reduces production costs while avoiding the use of expensive rare earth elements, and is more conducive to achieving stable quality control.

[0046] In terms of the preparation process, the introduction of trace amounts of titanium carbide / titanium diboride nanoparticles combined with ultrasonic melt treatment effectively refined the solidification microstructure, providing a uniform and fine initial microstructure foundation for subsequent rapid extrusion. This method significantly simplifies the complex thermomechanical processing procedures such as multi-stage homogenization and multi-directional forging commonly found in traditional processes. Furthermore, a stepped homogenization heat treatment is employed to further eliminate low-melting-point phases, homogenizing the microstructure and laying the structural foundation for efficient extrusion.

[0047] Regarding the mechanism of flame retardant performance, calcium in the alloy preferentially oxidizes at high temperatures to form a dense CaO surface layer, effectively blocking oxygen. The addition of aluminum and manganese helps to form a highly thermally stable dispersed nanophase. These dispersed phases can effectively pin grain boundaries and inhibit grain coarsening during rapid extrusion, while enhancing the stability of the microstructure beneath the oxide film and providing channels for element diffusion. This allows the alloy to rapidly form a continuous and complete protective oxide film when exposed to high temperatures, thereby synergistically improving the flame retardant response speed and reliability. By combining the introduction of trace nanoparticles with ultrasonic melt treatment, in-situ generation and uniform dispersion of nanoparticles are achieved. The microstructure is further refined through the heterogeneous nucleation of nanoparticles and the cavitation effect of power ultrasound. At the same time, nanoparticles can effectively fill defects in the surface oxide film at high temperatures, improving its self-healing ability and density.

[0048] Ultimately, this alloy can be rapidly extruded at 300-400℃ with an exit rate of 5-30 m / min, achieving high production efficiency, and its flame-retardant properties are superior to those in the comparative example. This invention successfully achieves synergistic optimization between material flame-retardant properties, rapid prototyping capability, production cost, and process simplification by combining composition design, nanoparticle reinforcement, melt ultrasonic treatment preparation process, and rapid extrusion process, demonstrating excellent comprehensive performance and promising prospects for industrial application.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A micro-alloyed, rapidly extruded, flame-retardant magnesium alloy, characterized in that, It is composed of the following components by mass percentage: aluminum 1.0-1.8%, calcium 0.3-0.4%, manganese 0.4-0.6%, nanoparticles 0-0.08%, unavoidable impurities ≤0.02%, and the balance being magnesium.

2. The microalloyed rapid extrusion flame-retardant magnesium alloy according to claim 1, characterized in that, The nanoparticles include titanium carbide nanoparticles and / or titanium diboride nanoparticles.

3. The microalloyed rapid extrusion flame-retardant magnesium alloy according to claim 1, characterized in that, The microalloyed rapid extrusion flame-retardant magnesium alloy has an alloying element content of ≤2.8%, belonging to a low alloy system.

4. The method for preparing the microalloyed rapid extrusion flame-retardant magnesium alloy according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Weigh the raw materials according to the stated mass percentage of the components; Among them, magnesium, aluminum, calcium, manganese and nanoparticles are derived from pure magnesium, pure aluminum, magnesium-calcium master alloy, magnesium-manganese master alloy, titanium carbide / aluminum master alloy, and titanium diboride / aluminum master alloy. S2. After melting pure magnesium, add pure aluminum, magnesium-calcium master alloy and magnesium-manganese master alloy until completely melted, then clean the slag and stir. After heat preservation, blow in high-purity argon gas to refine and clean the slag. After heating again, add titanium carbide / aluminum master alloy and / or titanium diboride / aluminum master alloy. After they are completely melted, perform ultrasonic treatment on the melt and clean the slag again to obtain low-alloy magnesium alloy melt. S3. Obtain a microalloyed magnesium alloy ingot by pouring the microalloyed magnesium alloy melt into a steel mold; S4. After homogenization treatment, the microalloyed magnesium alloy ingot is extruded and deformed and then air-cooled to room temperature to obtain a microalloyed rapid extrusion flame-retardant magnesium alloy.

5. The preparation method according to claim 4, characterized in that, In S1, the magnesium-calcium master alloy is Mg-20Ca, and the magnesium-manganese master alloy is Mg-3Mn.

6. The preparation method according to claim 4, characterized in that, The titanium carbide / aluminum master alloy in S1 is Al-5Ti-0.2C, and the titanium diboride / aluminum master alloy is Al-5Ti-1B.

7. The preparation method according to claim 4, characterized in that, The temperature at which the temperature is raised again in S2 is 680-720℃.

8. The preparation method according to claim 4, characterized in that, The parameters for ultrasonic treatment of the melt in S2 are: immersion depth in the melt 30mm, ultrasonic power 1200W, and ultrasonic time 120s.

9. The preparation method according to claim 4, characterized in that, The homogenization process in S4 specifically involves: performing a three-stage step homogenization process (330℃ / 4h + 450℃ / 3h + 480℃ / 1h) on a muffle furnace, followed by water quenching.

10. The preparation method according to claim 4, characterized in that, The extrusion deformation process in S4 specifically involves: before extrusion deformation, preheating the homogenized microalloyed magnesium alloy ingot at 300-400℃ for 60-120 min, and preheating the extrusion die at 300-400℃; the extrusion ratio is (10-70):1, and the extrusion exit rate is 5-30 m / min.