A low-cost magnesium alloy with high thermal stability and a preparation method thereof

Abstract

The application belongs to the technical field of metal materials, and discloses a low-cost magnesium alloy with high thermal stability and a preparation method thereof; the magnesium alloy comprises the following components in percentage by mass: aluminum: 0.3-2.0%, manganese: 0.2-0.8%, calcium: 0.15-0.5%, additive elements: 0-1.15%, the additive elements being one or any combination of cerium, zinc or scandium, the rest being magnesium and inevitable impurities, and the total amount of the inevitable impurities being ≤0.05%. The preparation method comprises the following processes: melting, casting, solid solution and multi-pass rolling, and effectively controls the grain boundary segregation, the size, number density, type and thermal stability of the second phase in the magnesium alloy, so as to slow down the grain boundary movement rate, thereby improving the thermal stability of the low-alloy magnesium alloy.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal materials, in particular relates to a low-cost magnesium alloy with high thermal stability and a preparation method thereof. BACKGROUND

[0002] As a light-weight structural material, magnesium alloy has the advantages of low density, high specific strength, good electromagnetic shielding property, etc., and has a wide application prospect in the fields of automobile, communication, aerospace, etc. Due to the large Hall-Petch coefficient of magnesium and its alloys (the larger the Hall-Petch coefficient, the more obvious the strengthening effect of grain refinement), fine-grained magnesium alloy generally has high strength. However, the thermal stability of fine-grained magnesium alloy is limited, and when exposed to high temperature, the grains will rapidly coarsen, and the service performance of the alloy will rapidly decrease. In addition, improving the thermal stability of the alloy will increase the deformation resistance of the alloy, and cracking will occur during the thermal mechanical processing, resulting in low production efficiency. Therefore, how to prepare a new type of magnesium alloy with high thermal stability and deformation resistance by reducing the cost and simplifying the process is a technical problem to be solved at present. SUMMARY

[0003] In order to solve the above technical problems, the present application provides a low-cost magnesium alloy with high thermal stability, wherein the aluminum is 0.3-2.0%, the manganese is 0.2-0.8%, the calcium is 0.15-0.5%, the additive element is 0-1.15%, the additive element is one or any combination of cerium, zinc or scandium, the rest is magnesium and unavoidable impurities, and the total amount of unavoidable impurities is ≤0.05% by mass percentage.

[0004] (1) Under the protection of argon, pure magnesium, pure aluminum, magnesium-manganese intermediate alloy, magnesium-calcium intermediate alloy and additive element alloy are sequentially added, and heated and melted at 650-680℃; after uniform stirring, refining and degassing, and slag removal, an alloy liquid is obtained, wherein the additive element alloy is one or any combination of magnesium-cerium intermediate alloy or magnesium-scandium intermediate alloy or pure zinc,

[0005] (2) The alloy liquid obtained in step (1) is cast into a mold to obtain a cast plate;

[0006] (3) The cast plate obtained in step (2) is subjected to solid solution treatment under an argon atmosphere and then cooled to room temperature, wherein the solid solution treatment is at a solid solution temperature of 400-550℃ for 3-10 hours; and then subjected to multi-pass small reduction rolling treatment to obtain a low-cost magnesium alloy with high thermal stability; wherein the multi-pass small reduction rolling treatment is 8-15 passes, each pass reduction is 5%-20%, the total reduction is ≥80%, and each pass is subjected to heat preservation at 250-350℃ for 5-20 minutes before rolling, and the rolling temperature is 230-340℃.

[0007] Further, the aluminum is 0.4-1.5%, the manganese is 0.3-0.7%, and the calcium is 0.2-0.3% by mass percentage.

[0008] Further, the additive element is 0.1-0.7% by mass percentage.

[0009] Compared with the prior art, the present application has the following characteristics:

[0010] Compared with the prior art, the present application reduces the alloy addition amount and the rare earth addition amount (even without adding rare earth), the total amount of added alloy element composition is ≤4.45wt.%, and simplifies the process, which is suitable for industrial production. Through the synergistic control effect of the interaction, ratio, process and process parameters of alloy components, the following advantages are obtained:

[0011] 1) The present application can effectively control the type, size, distribution, number density, stability of the second phase and grain boundary of the magnesium alloy, including: forming a high-density second phase with a size less than 10 nanometers; the added elements form a second phase with a "core-shell" structure, form grain boundary co-segregation, and multiple phases greatly improve the second phase Zener pinning and solute drag effect, effectively hinder the movement of grain boundaries under high temperature conditions, and ensure that the alloy has ultra-high thermal stability.

[0012] 2) Compared with the existing high alloy system or high rare earth magnesium alloy, the present application reduces the content of alloy elements and simplifies the process, and the alloy can still maintain a grain size much smaller than that obtained by the prior art under the condition of higher heat treatment temperature and longer treatment time than the prior art. Since the smaller the grain size, the better the thermal stability of the alloy, therefore, the thermal stability of the alloy obtained by the present application is still better than that of the alloy obtained by the prior art under the condition of higher temperature treatment.

[0013] 3) The present application breaks through the technical bottleneck of the prior art which is mainly used for preparing small-size high-thermal-stability alloy, and can realize industrial production. In addition, the present application also synchronously increases the deformation resistance of the alloy, and effectively suppresses the cracking generated in the thermal mechanical processing process. DETAILED DESCRIPTION

[0014] Example 1

[0015] Taking Mg-0.60Al-0.50Mn-0.20Ca-0.30Ce alloy as an example (Al: 0.60%, Mn: 0.50%, Ca: 0.20%, Ce: 0.30% by mass percentage; unavoidable impurities total ≤0.05%, and the balance is magnesium), the preparation method is as follows:

[0016] (1) Under argon protection, pure magnesium, pure aluminum, magnesium-manganese intermediate alloy, magnesium-calcium intermediate alloy and magnesium-cerium intermediate alloy are added in sequence and heated to melt at 660°C; after uniform stirring, refining, degassing and slag removal, alloy liquid is obtained;

[0017] (2) The alloy liquid obtained in step (1) is cast into a sub-rapidly solidified water-cooled copper mold at room temperature to obtain a plate, and then solid solution treatment is carried out under argon protection, i.e. after being kept at 450-460°C for 4 hours, it is cooled to room temperature to obtain a solid-solution-treated plate;

[0018] (3) The solid-solution-treated plate obtained in step (2) is rolled for 13 passes with a total reduction of ~85%, wherein the reduction of each of the first 4 passes is ~20%, and the reduction of each of the last 9 passes is ~10%; before each pass, it is kept at 300°C for 10 minutes, and the rolling temperature of each pass is 285°C, to obtain a Mg-0.60Al-0.50Mn-0.20Ca-0.30Ce alloy.

[0019] The alloy obtained in step (3) of this example has a uniform fine-grained structure after long-term treatment at room temperature and high temperature, and even after being kept at 480°C for 20 hours, the average grain size can still be maintained at ~13 microns or so, and the alloy has high-temperature thermal stability.

[0020] Example 2

[0021] Taking Mg-1.00Al-0.70Mn-0.30Ca-0.10Ce-0.10Zn alloy as an example (Al: 1.00%, Mn: 0.70%, Ca: 0.30%, Ce: 0.10%, Zn: 0.10% by mass; unavoidable impurities ≤0.05% in total, and the balance is magnesium), the preparation method is as follows:

[0022] (1) Under argon protection, pure magnesium, pure aluminum, pure zinc, magnesium-manganese intermediate alloy, magnesium-calcium intermediate alloy and magnesium-cerium intermediate alloy are added in sequence and heated to melt at 675°C, and then after uniform stirring, refining, degassing and slag removal, alloy liquid is obtained;

[0023] (2) The alloy liquid obtained in step (1) is cast into a sub-rapidly solidified water-cooled copper mold at room temperature to obtain a plate, and then solid solution treatment is carried out under argon protection, i.e. after being kept at 465-480°C for 3 hours, it is cooled to room temperature to obtain a solid-solution-treated plate;

[0024] (3) The solution treated plate obtained in step (2) is rolled for 8 passes with a total reduction of ~83%, and in the first 4 passes, the reduction of each pass is ~20%, and the rolling temperature is 310°C with 10 minutes holding at 325°C between passes; in the last 4 passes, the reduction of each pass is ~20%, and the rolling temperature is 250°C with 15 minutes holding at 275°C between passes; a high thermal stability low cost Mg-1.00Al-0.70Mn-0.30Ca-0.10Ce-0.10Zn alloy is obtained.

[0025] The alloy obtained in step (3) of this example has a uniform fine grain structure after long time treatment at room temperature and high temperature, and even after 10 hours holding at 510°C, the average grain size can still be maintained at ~17 microns or so, and the alloy has high thermal stability.

[0026] Example 3

[0027] Taking Mg-1.50Al-0.70Mn-0.30Ca-0.20Sc alloy as an example (in terms of mass percentage: Al: 1.50%, Mn: 0.70%, Ca: 0.30%, Sc: 0.20%, unavoidable impurities: ≤0.05%, and the balance being magnesium), the preparation method is as follows:

[0028] (1) Under argon protection, pure magnesium is added in sequence, and heated and melted at 650°C; then pure aluminum and magnesium-manganese intermediate alloy are added, and heated and melted at 670°C; then magnesium-calcium intermediate alloy is added, and heated and melted at 670°C; then magnesium-scandium intermediate alloy is added, and heated and melted at 670°C; after stirring uniformly at 660°C, refining, degassing and slag removal, alloy liquid is obtained;

[0029] (2) The alloy liquid obtained in step (1) is cast into a sub-rapid solidification water-cooled copper mold at room temperature to obtain a plate, and then solution treated under argon protection, and after holding at 425-545°C for 6 hours, cooled to room temperature to obtain a solution treated plate;

[0030] (3) The solution treated plate obtained in step (2) is rolled for 15 passes with a total reduction of ~88%, and in the first 8 passes, the reduction of each pass is ~10%, and the rolling temperature is 340°C with 5 minutes holding at 350°C between passes; in the last 4 passes, the reduction of each pass is ~15%, and the rolling temperature is 275°C with 10 minutes holding at 300°C between passes; in the last 2 passes, the reduction of each pass is ~20%, and the rolling temperature is 240°C with 15 minutes holding at 250°C between passes; a high thermal stability low cost Mg-1.50Al-0.70Mn-0.3Ca-0.2Sc alloy is obtained.

[0031] The alloy obtained in step (3) of the embodiment has a uniform fine-grained structure after long-time treatment at room temperature and high temperature, and even after holding at 550°C for 1 hour, the average grain size can be maintained at about 18 microns, and the alloy has high-temperature thermal stability.

[0032] Example 4

[0033] For example, the Mg-0.80Al-0.50Mn-0.30Ca-0.10Zn-0.10Ce-0.10Sc alloy (in terms of mass percentage: Al: 0.80%, Mn: 0.50%, Ca: 0.30%, Zn: 0.10%, Ce: 0.10%, Sc: 0.10%, and unavoidable impurities ≤0.05%, and the balance being magnesium) is prepared as follows:

[0034] (1) Under argon protection, pure magnesium, pure aluminum, pure zinc, magnesium-manganese intermediate alloy, magnesium-calcium intermediate alloy, and magnesium-cerium and magnesium-scandium intermediate alloy are sequentially added, and the mixture is heated and melted at 650°C, and then stirred uniformly, refined, degassed, and cleaned, to obtain an alloy liquid;

[0035] (2) The alloy liquid obtained in step (1) is cast into a sub-rapidly solidified water-cooled copper mold at room temperature to obtain a plate, and then the plate is subjected to solid solution treatment under argon protection, wherein the solid solution treatment is performed at a temperature of 410-510°C for 10 hours, and then cooled to room temperature, to obtain a solid-solution-treated plate;

[0036] (3) The solid-solution-treated plate obtained in step (2) is subjected to 12 passes of rolling with a total reduction of about 84%, wherein in the first 5 passes, the reduction of each pass is about 20%, and the temperature is maintained at 325°C for 5 minutes between passes; and in the last 7 passes, the reduction of each pass is about 10%, and the temperature is maintained at 275°C for 15 minutes between passes, to obtain the Mg-0.80Al-0.50Mn-0.30Ca-0.10Zn-0.10Ce-0.10Sc alloy.

[0037] The low-alloy magnesium alloy obtained in step (4) of the embodiment has high thermal stability, and the grain size is less than 11.5 microns after holding at 480°C for 20 hours.

[0038] Example 5

[0039] For example, the Mg-0.60Al-0.55Mn-0.15Ca alloy (in terms of mass percentage: Al: 0.60%, Mn: 0.55%, Ca: 0.15%, and unavoidable impurities ≤0.05%, and the balance being magnesium) is prepared as follows:

[0040] (1) Under argon protection, pure magnesium, pure aluminum and magnesium-manganese intermediate alloy and magnesium-calcium intermediate alloy are added successively and heated to melt at 655°C; after stirring, refining, degassing and slag removal, alloy liquid is obtained;

[0041] (2) The alloy liquid obtained in step (1) is cast into a sub-rapidly solidified water-cooled copper mold at room temperature to obtain a plate, and then solid solution treatment is carried out under argon protection, wherein the solid solution treatment is: heating at 450-510°C for 6 hours and then cooling to room temperature, to obtain a solid solution plate;

[0042] (3) The solid solution plate obtained in step (2) is rolled for 13 passes with a total reduction of ~84%, wherein the reduction of each pass is ~20% in the first 4 passes and ~10% in the last 9 passes, and the rolling temperature is 290°C, and the alloy Mg-0.60Al-0.55Mn-0.15Ca is obtained.

[0043] The alloy obtained in step (3) of the example has a uniform fine-grained structure after long-term treatment at room temperature and high temperature, and even after heating at 510°C for 10 hours, the average grain size can still be maintained at ~18 microns.

[0044] Example 6

[0045] Taking Mg-1.20Al-0.40Mn-0.30Ca-0.10Ce-0.10Zn alloy as an example (according to the mass percentage of components: Al: 1.20%, Mn: 0.40%, Ca: 0.30%, Ce: 0.10%, Zn: 0.10%, and the sum of unavoidable impurities ≤0.05%, and the balance is magnesium), the preparation method is as follows:

[0046] (1) Under argon protection, pure magnesium, pure aluminum, pure zinc and magnesium-manganese intermediate alloy, magnesium-calcium intermediate alloy and magnesium-cerium intermediate alloy are added successively and heated to melt at 675°C; after stirring, refining, degassing and slag removal, alloy liquid is obtained;

[0047] (2) The alloy liquid obtained in step (1) is cast into a sub-rapidly solidified water-cooled copper mold to obtain a plate, and then solid solution treatment is carried out under argon protection, wherein the solid solution treatment is: heating at 420-520°C for 5 hours and then cooling to room temperature, to obtain a plate;

[0048] (3) The plate obtained in step (2) is rolled for 10 passes with a total reduction of ~80%, and in the first 5 passes, the reduction of each pass is ~20%, and the rolling temperature is 300°C with 5 minutes of holding between passes at 325°C; in the last 5 passes, the reduction of each pass is ~10%, and the rolling temperature is 240°C with 15 minutes of holding between passes at 250°C, to obtain the Mg-1.20Al-0.40Mn-0.30Ca-0.10Ce-0.10Zn alloy.

[0049] The alloy obtained in step (3) of the example has a uniform fine-grained structure after long-time treatment at room temperature and high temperature, and even after 1 hour of holding at 550°C, the average grain size can still be maintained at ~19 microns.

[0050] Example 7

[0051] Taking the Mg-0.40Al-0.50Mn-0.30Ca-0.20Zn alloy as an example (with the components in mass percentage being: Al: 0.40%, Mn: 0.50%, Ca: 0.30%, Zn: 0.20%, unavoidable impurities totaling ≤0.05%, and the balance being magnesium), the preparation method is as follows:

[0052] (1) Under argon protection, pure magnesium is first added and heated to melt at 660°C; then pure aluminum, pure zinc, and a magnesium-manganese intermediate alloy are added and heated to melt at 660°C; then a magnesium-calcium intermediate alloy is added and heated to melt at 660°C; after uniform stirring at 660°C, refining, degassing, and slag removal are performed to obtain an alloy liquid;

[0053] (2) The alloy liquid obtained in step (1) is cast into a sub-rapid solidification water-cooled copper mold to obtain a plate, and then solid solution treatment is performed under argon protection, wherein the solid solution treatment is performed at 450-520°C for 7 hours and then cooled to room temperature to obtain a solid solution plate;

[0054] (3) The solid solution plate obtained in step (2) is rolled for 12 passes with a total reduction of ~81%, and in the first 7 passes, the reduction of each pass is ~15% with 10 minutes of holding at 300°C between passes, and the rolling temperature is 290°C; in the last 5 passes, the reduction of each pass is ~10% with 15 minutes of holding at 250°C between passes, and the rolling temperature is 240°C, to obtain the Mg-0.40Al-0.50Mn-0.30Ca-0.20Zn alloy.

[0055] The alloy obtained in step (3) of the example has a uniform fine-grained structure after long-time treatment at room temperature and high temperature, and even after 5 hours of holding at 500°C, the average grain size can still be maintained at ~14 microns.

[0056] Comparative Example 1: Article source: Journal of Materials and Science, 50 (2015) 4940-4951

[0057] Article title: Microstructural stability and grain growth kinetics in an extruded fine-grained Mg-Gd-Y-Zr alloy

[0058] Authors: R Alizadeh, R Mahmudi, A.H.W Ngan et al.

[0059] The comparative example discloses an annealed Mg-9Gd-4Y-0.4Zr (wt.%) alloy, the preparation steps include melting, casting, extrusion and heat treatment. After the alloy is heat treated at 400℃ for 2h, the average grain size of the alloy is 16.9μm, and after further heat treatment at 450℃ for 2h, the average grain size of the alloy is ~49.2μm. The total alloy additive content of the comparative example alloy is 13.4wt.%, among which the content of rare earth (Gd, Y) elements accounts for the largest proportion, which is 13.0wt.%, and the price of Gd is higher among the rare earth elements, which is much higher than that of rare earth Ce and Sc, while the maximum additive amount of the alloy of the present application is 4.45wt.%, and the rare earth can be selectively added or not added in the alloy, and the content of rare earth is ≤0.7% (mainly Ce and Sc), therefore compared with the present application, the raw material cost of comparative example 1 is higher, in addition, the process adopted by comparative example 1 is significantly different from that of the present application. After the alloy of comparative example 1 is heat treated at 400℃ for 2h, the average grain size of the alloy is 16.9μm, and after further heat treatment at 450℃ for 2h, the average grain size of the alloy is ~49.2μm, among which the alloy of example 7 (Mg-0.40Al-0.50Mn-0.30Ca-0.20Zn alloy, the total alloy additive amount is 1.4wt.%, and does not contain any rare earth element) of the present application is taken as an example. The alloy obtained by the example has a uniform fine-grained structure after long-time treatment at room temperature and high temperature, and the average grain size remains at ~14μm after heat preservation at 500℃ for 5h. The total additive amount of the alloy of example 7 of the present application is lower than that of the alloy obtained by comparative example 1, and the alloy of example 7 of the present application does not use rare earth element, and the processes adopted by the two are significantly different.

[0060] According to the prior art reports, the higher the heat treatment temperature and the longer the time, the larger the grain size. When comparing Example 7 of the present application with Comparative Example 1, the heat treatment temperature and time of Example 7 of the present application are higher than those disclosed in Comparative Example 1. According to the prior art reports, the smaller the total amount of alloy and rare earth addition, the higher the heat treatment temperature and the longer the time, and the larger the grain size. According to the above conclusion, the grain size of the alloy after heat treatment of Example 7 of the present application should be larger than that obtained in Comparative Example 1. However, the result is that the grain size of the alloy obtained in Example 7 of the present application after high temperature and long time treatment is smaller than that of the alloy obtained in Comparative Example 1. Therefore, compared with Comparative Example 1, the grain refinement effect of the present application is better. Since the uniform and fine grain size effect is better, the thermal stability of the alloy is better. Therefore, compared with Comparative Example 1, the high thermal stability of the alloy obtained in the present application is better.

[0061] Comparative Example 2: Article source: Materials Today Communications, 34 (2023) 105106

[0062] Article title: Static recrystallization and precipitation behavior of forged and annealed Mg-8.7Gd-4.18Y-0.42Zr magnesium alloy

[0063] Author: Ling Zhang, Xiaoyu Wu, Xindong Yang, et al.

[0064] Zhang et al. discloses an annealed Mg-8.7Gd-4.18Y-0.42Zr (wt.%) alloy, the preparation steps include melting, semi-continuous casting, solid solution, forging, annealing heat treatment. The grain size of the alloy is about 18.3 μm after heat treatment at 350℃ for 2h. The total addition amount of the alloy of the comparative example is 13.3%, among which the proportion of expensive rare earth (Gd, Y) elements is the highest, which is 12.88wt.%, and the price of Gd is much higher than that of rare earth Ce and Sc, and the maximum addition amount of the alloy of the present application is 4.45wt.%, and the rare earth can be selectively added or not added in the alloy, and the rare earth content is ≤0.7% (mainly Ce and Sc), so compared with the present application, the raw material cost of comparative example 2 is higher, in addition, the process of comparative example 2 is significantly different from that of the present application. The grain size of the alloy obtained by comparative example 2 is about 18.3 μm after heat treatment at 350℃ for 2h. Among them, taking example 7 (Mg-0.40Al-0.50Mn-0.30Ca-0.20Zn alloy, the total alloy addition amount is 1.4wt.%, and no rare earth element is contained) of the present application as an example, the alloy obtained by the example has a uniform fine grain structure after long time treatment at room temperature and high temperature, and the average grain size is maintained at about 14 microns after heat preservation at 500℃ for 5 hours. According to the existing technology, the higher the heat treatment temperature and the longer the time, the larger the grain size. When comparing example 7 of the present application with comparative example 2, the heat treatment temperature and time of example 7 of the present application are higher than those of comparative example 2. According to the existing technology, the smaller the total addition amount of the alloy and the rare earth addition amount, the higher the heat treatment temperature and the longer the time, the larger the grain size. According to the above conclusion, the grain size of the alloy of example 7 of the present application after heat treatment should be larger than that of comparative example 2. However, the result is that the grain size of the alloy obtained by example 7 of the present application after high temperature and long time treatment is smaller than that of the alloy obtained by comparative example 2. Therefore, compared with comparative example 2, the grain refinement effect of the present application is better. Since the uniform refinement effect of the grain size is better, the thermal stability of the alloy is better, so compared with comparative example 2, the high thermal stability of the alloy obtained by the present application is better.

[0065] Compared with the prior art, the alloy obtained by the application has a uniform fine-grained structure after long-time treatment at room temperature and high temperature, and even in the case of high-temperature treatment, the high-thermal-stability alloy obtained is superior to the alloy obtained by the prior art. In the case of reducing the alloy addition amount and the rare earth addition amount or not adding the rare earth element, the process is simplified, and in the case of higher treatment temperature and longer treatment time than the prior art, the obtained alloy has finer and more uniform grains, and therefore the high-thermal-stability alloy obtained is superior to the alloy obtained by the prior art. In addition, the components, proportions, processes and parameters of all the embodiments of the application are different, and the grain sizes of the obtained alloys are different, i.e. the high-temperature thermal stabilities are different, so it is concluded that the optimal effect of the alloy obtained by the application is realized by the synergistic regulation of the interaction of alloy components, the proportion and the process and process parameters. In addition, the application also synchronously increases the deformation resistance of the alloy, effectively inhibits the cracking generated in the thermal mechanical processing process, and is suitable for industrial production.

Claims

1. A low-cost magnesium alloy with high thermal stability, characterized in that: By mass percentage, aluminum: 0.3-2.0%, manganese: 0.2-0.7%, calcium: 0.15-0.3%, with the remainder being magnesium and unavoidable impurities, the total of which is ≤0.05%; its preparation method includes the following steps: (1) Under argon protection, pure magnesium, pure aluminum, magnesium-manganese master alloy and magnesium-calcium master alloy are added in sequence and heated to 650-680℃ to melt; after stirring evenly, refining and degassing and removing slag, alloy liquid is obtained. (2) The alloy liquid obtained in step (1) is poured into a mold to obtain a casting plate; (3) The cast plate obtained in step (2) is subjected to solution treatment in an argon atmosphere and then cooled to room temperature. The solution treatment is: solution temperature 450-510℃, heat preservation for 3-10 hours; and then subjected to multiple passes of small reduction rolling to obtain a low-cost magnesium alloy with high thermal stability. The multi-pass small reduction rolling process is as follows: 8-15 passes, each reduction is 5%-20%, the total reduction is ≥80%, and the temperature is kept at 250-350℃ for 5-20 minutes before each pass rolling, and the rolling temperature is 230-340℃. The high thermal stability low-cost magnesium alloy forms a high-density second phase with a size of less than 10 nanometers. The added elements form a second phase with a "core-shell" structure, and the formation of grain boundary co-segregation and multi-component phases greatly improve the Zener pinning and solute dragging effect of the second phase, effectively hindering the movement of grain boundaries under high temperature conditions and ensuring that the alloy has ultra-high thermal stability.

2. The low-cost magnesium alloy with high thermal stability according to claim 1, characterized in that: The aluminum, by weight percentage: 0.4-1.5%, Manganese: 0.3-0.7%, Calcium: 0.2-0.3%.