High-performance magnesium alloy with tension-compression yield symmetry and preparation method thereof

Abstract

The application belongs to the field of metal materials and metallurgy technology, and particularly relates to a high-performance magnesium alloy with tensile-compressive yield symmetry and a preparation method thereof. The alloy comprises the following components and their mass percentages: Zn 7.0-9.0%, Dy 0.5-1.5%, Gd 0.5-1.5%, Zr 0.3-0.6%, Pr 0.1-0.5%, Bi 0.05-0.20%, Sn 0.05-0.15%, impurity elements Si, Fe, Cu and Ni with a total amount of not more than 0.03%, and the balance of Mg. The magnesium alloy ingot is prepared by a simple conventional casting method, is subjected to surface turning after homogenization annealing, is heated to a certain temperature, and is subjected to reverse extrusion by using a reverse extrusion device to obtain an extruded rod. The rod prepared by the above process has tensile-compressive yield symmetry at room temperature, and has high strength and good elongation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal materials and metallurgy, and particularly relates to a high-performance magnesium alloy with tensile-compressive yield symmetry and a preparation method thereof. BACKGROUND

[0002] Magnesium alloys have attracted extensive attention in the fields of automobiles and aviation due to their small density, high specific strength and specific stiffness. In addition, the good biocompatibility makes Mg alloys have great development potential in biomedical materials. However, the poor strength and corrosion resistance limit the development of magnesium alloys. Alloying is the most common method to improve the mechanical properties and corrosion resistance of magnesium alloys. The large solid solubility of rare earth elements can lead to strong solid solution strengthening effect, among which Mg-Gd alloy is the most attractive. The solid solubility of Gd in Mg changes significantly with temperature, so Mg-Gd alloy also shows significant age hardening effect. In addition, the maximum solid solubility of Dy in magnesium is close to 25.8%, and its solid solubility concentration at high temperature is more significant than that of Gd, and the solid solubility is also very sensitive to temperature. Therefore, Dy plays a similar role to Gd in Mg-Gd binary alloys.

[0003] It has been found that adding different contents of Zn element on the basis of Mg-Gd binary alloy can lead to different second phases. With the increase of Zn / Gd atomic ratio, Mg-Gd-Zn gradually forms LPSO phase, W phase and I phase. Since Kawamure et al. prepared Mg 97 Zn1Y2 alloy, LPSO phase has attracted extensive research. LPSO phase has high melting point and hardness, which is beneficial to improve the yield strength and high temperature resistance of the alloy. However, a large amount of LPSO phase is not conducive to the plasticity of the alloy. In contrast, W phase is a hard and brittle phase, and it has a non-coherent relationship with the a-Mg matrix, which is easy to become a nucleation site for micro-cracks in the alloy. Unlike W phase, the special orientation relationship between I phase and Mg matrix makes them have high interface bonding strength, which has a significant contribution to plasticity. I phase has low interfacial energy during solidification and is not easy to coarsen and grow at high temperature, and its stability is good. Liu et al. found that I phase in extruded Mg 95.9 Zn 3.5 Gd 0.6 alloy still has good stability at 440 ℃, and the corrosion resistance of the phase is also good. The as-cast alloy will form serious cylindrical texture after being extruded into a rod, and the strong texture is not conducive to the tensile-compressive yield symmetry of the alloy. However, during the hot deformation process containing I phase, the fine I phase promotes the dynamic recrystallization process through the particle stimulated nucleation mechanism, which is conducive to the weakening of the texture strength; and a large amount of nanometer-sized I phase is precipitated in the process, which can pin dislocations and grain boundary movement, and has a strong dispersion strengthening effect.

[0004] The addition of Sn can reduce the stacking fault energy of the alloy, thereby promoting the precipitation of the second phase; Sn itself can also form a stable high-temperature-resistant precipitated phase, which can improve the fluidity and thermal stability of the alloy during casting. In addition, Sn has a high solubility in Mg alloy (3.35 at%), and its solubility decreases sharply with the decrease of temperature, so it has a good aging hardening effect in Mg alloy. Similarly, Bi micro-alloying can also play a role in refining the grains. Pr is a kind of light rare earth element, and its research in Mg alloy is relatively less. The present application aims to explore the combined effect of their micro-alloying on I phase containing alloy. SUMMARY

[0005] In view of the problems existing in the prior art, the present application provides a high-performance magnesium alloy with tensile-compressive yield symmetry and a preparation method thereof. The process method is low in cost and simple and easy to implement. The obtained magnesium alloy has high strength at room temperature, good elongation at room temperature and tensile-compressive yield symmetry, so that the magnesium alloy has more superior mechanical properties and good formability than traditional commercial magnesium alloy.

[0006] The technical scheme of the present application is:

[0007] A high-performance magnesium alloy with tensile-compressive yield symmetry, wherein the components and their mass percentages in the alloy are as follows: Zn 7.0-9.0%, Dy 0.5-1.5%, Gd 0.5-1.5%, Zr 0.3-0.6%, Pr 0.1-0.5%, Bi 0.05-0.20%, Sn 0.05-0.15%, the total amount of impurity elements Si, Fe, Cu and Ni is not more than 0.03%, and the balance is Mg.

[0008] Further, the high-performance magnesium alloy with tensile-compressive yield symmetry described above has an atomic ratio of Dy / Gd of 0.5-1 and an atomic ratio of Zn / (Gd and Dy) of 3.5-8.5.

[0009] Further, the high-performance magnesium alloy with tensile-compressive yield symmetry described above has an atomic ratio of Dy / Gd of 0.5-1 and an atomic ratio of Zn / (Gd and Dy) of 3.5-8.5.

[0010] Further, the high-performance magnesium alloy with tensile-compressive yield symmetry described above has an atomic ratio of Dy / Gd of 0.5-1 and an atomic ratio of Zn / (Gd and Dy) of 3.5-8.5.

[0011] Further, the high-performance magnesium alloy with tensile-compressive yield symmetry has the following components and mass percentages: Zn 7%, Dy 1%, Gd 1.5%, Pr 0.3%, Bi 0.05%, Sn 0.1%, and Zr 0.5%, and the total amount of impurity elements Si, Fe, and Ni is less than 0.03%, and the rest is Mg.

[0012] Further, the high-performance magnesium alloy with tensile-compressive yield symmetry has the following components and mass percentages: Zn 8%, Dy 1.5%, Gd 1.5%, Pr 0.5%, Bi 0.1%, Sn 0.15%, and Zr 0.4%, and the total amount of impurity elements Si, Fe, and Ni is less than 0.02%, and the rest is Mg.

[0013] Further, the high-performance magnesium alloy with tensile-compressive yield symmetry has the following components and mass percentages: Zn 9%, Dy 1.5%, Gd 1.5%, Pr 0.4%, Bi 0.15%, Sn 0.1%, and Zr 0.5%, and the total amount of impurity elements Si, Fe, and Ni is less than 0.02%, and the rest is Mg.

[0014] The preparation method of the high-performance magnesium alloy with tensile-compressive yield symmetry comprises the following steps:

[0015] (1) The pure Mg, pure Zn, pure Dy, Mg-30% Gd intermediate alloy, pure Pr, pure Bi, pure Sn, and Mg-30% Zr intermediate alloy are weighed according to the component ratio, and the oxide scales on the surfaces of all raw materials are polished off by sandpaper;

[0016] (2) Before melting, all raw materials are preheated in an oven at a temperature of 100-150 ℃ for 2-3 h;

[0017] (3) The melting furnace is heated to 700-750 ℃, the preheated pure Mg, pure Dy, pure Pr, and Mg-30% Gd intermediate alloy are put into the crucible, and the crucible cover is covered after being sprinkled with a covering agent; after the above-mentioned raw materials are completely melted, the crucible cover is opened, the slag on the surface of the alloy liquid is removed, and the molten liquid is manually stirred for 1-4 min to uniformly mix, and then a layer of covering agent is sprinkled and the cover is covered again;

[0018] (4) continue to heat to 780~800℃, then add Mg-30%Zr intermediate alloy, after the intermediate alloy is completely melted, sprinkle appropriate amount of covering agent while stirring; the alloy melt temperature is reduced to 700~720℃, then add pure Zn, pure Bi and pure Sn, after they are completely melted, fully stir the melt for 1~3 min, then sprinkle a layer of covering agent, cover the lid, and keep at 700~750℃ for 10~20 min; the alloy melt is fully stirred again for 1~3 min, then keep at 690~710℃ for 10~20 min, then remove the slag and pour; the surface slag of the melt needs to be removed before pouring, and the pouring process needs to be carried out under a protective gas;

[0019] (5) the ingot obtained after pouring in step (4) is placed in a resistance heating furnace for homogenization treatment, and the homogenization treatment system is: keeping at 400~450 ℃ for 10~15 h;

[0020] (6) the ingot after homogenization in step (5) is surface turned to match the inner diameter and length of the extrusion cylinder of the extruder; the processed ingot is heated to 250~300 ℃ in a heating furnace, and kept for 1~2 h;

[0021] (7) the ingot after heating in step (6) is placed in a preheated extrusion cylinder for extrusion, the extrusion speed is 1.0~5.0 mm / s, the preheating temperature of the extrusion cylinder is 250~300 ℃, and the extrusion ratio is 10~20:1.

[0022] Further, in the above preparation method of the high-performance magnesium alloy with tensile-compressive yield symmetry, the protective gas in step (4) is SF6+CO2+air mixed gas, and the volume ratio of SF6:CO2:air is 0.5:40:50.

[0023] Further, in the above preparation method of the high-performance magnesium alloy with tensile-compressive yield symmetry, the mechanical property indexes of the prepared high-performance magnesium alloy with tensile-compressive yield symmetry are as follows: for tensile test, the room temperature ultimate tensile strength is 320~350 MPa, the room temperature yield strength is 260~300 MPa, and the room temperature elongation rate is greater than 23%; for compression test, the room temperature ultimate compression strength is 400~600 MPa, and the room temperature compression yield strength is 250~300 MPa; the tensile-compressive yield ratio of the alloy is 0.9~1.1.

[0024] Advantages and beneficial effects of the present application:

[0025] (1) The magnesium alloy prepared by the present application has higher strength at room temperature and higher elongation rate at room temperature compared with other conventional magnesium alloys, is easy to prepare magnesium alloy deformation material, and is convenient for large-scale production.

[0026] (2) The process is simple, the used equipment is conventional general equipment, easy to transplant and operate, low cost, can obviously improve the problem of alloy deformation difficulty, can solve the problem of low material yield due to difficulty in preparing deformation material of magnesium alloy, limit the application of magnesium alloy, and can also expand the application field of magnesium alloy. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Tensile and compressive stress-strain curves of the magnesium alloy prepared in the present application. DETAILED DESCRIPTION

[0028] The tensile and compressive stress-strain curves of the magnesium alloy prepared in the present application are shown in the following figure. Figure 1 The yield strength and tensile strength of the alloy are 276 and 325 MPa respectively, and the elongation is 24% in the tensile process; the compressive test results show that the yield strength and compressive strength of the alloy are 265 and 540 MPa respectively; the tensile and compressive yield ratio of the alloy is 1.04. The specific embodiments of the present application are further described in detail below, and the embodiments of the present application are used to illustrate the present application rather than limit the present application. Simple improvements of the present application according to the essence of the present application all belong to the scope of the present application.

[0029] In the following examples, Mg, Zn, Dy, Pr, Bi and Sn are added in the form of magnesium ingot (99.95%), zinc ingot (99.95%), dysprosium ingot (99.95%), praseodymium ingot (99.95%), bismuth ingot (99.95%) and Sn strip (99.95%), and Gd and Zr are added in the form of intermediate alloy, and the mass fraction of each intermediate alloy is: Mg-30% Gd and Mg-30% Zr.

[0030] In the following examples, the protective gas used in the alloy casting process is a mixed gas of SF6+CO2+air, and the volume ratio of SF6:CO2:air is 0.5:40:50.

[0031] In the following examples, the covering agent used in the alloy smelting process is a special reagent for magnesium alloy. Example 1

[0032] In this embodiment, the mass percentage of each component in the alloy is: Zn 7%, Dy 1%, Gd 1.5%, Pr 0.3%, Bi 0.05%, Sn 0.1% and Zr 0.5%, the atomic ratio of Dy / Gd is 0.64, the atomic ratio of Zn / (Gd and Dy) is 6.9, the total amount of impurity elements Si, Fe and Ni is 0.03%, and the balance is Mg. The preparation method of the alloy comprises the following steps:

[0033] The total amount of 3 Kg of corresponding metal ingots and master alloys is weighed according to the above ingredients, and the oxide scales on the surfaces of all raw materials are polished off by sandpaper. Then the weighed metal ingots and master alloys are placed into an oven at a temperature of 150 ℃ for 2 h of preheating. The preheated pure Mg, pure Dy, pure Pr and Mg-30% Gd master alloy are first placed into a melting furnace preheated to 700 ℃ for melting. A covering agent needs to be added during the melting process. After the above raw materials are melted, the alloy liquid is manually stirred for 2 min to remove the slag on the surface of the alloy liquid and to sprinkle the covering agent on the surface for protection. Then the alloy liquid in the smelting furnace is heated to 780 ℃, and the Mg-30% Zr master alloy is added at one time. After the master alloy is completely melted, the alloy liquid is fully stirred. The temperature of the alloy liquid is reduced to 720 ℃, and the pure Zn, pure Bi and pure Sn master alloy is added. After the master alloy is completely melted, the melt is fully stirred for 3 min, a layer of covering agent is sprinkled, and the lid is covered. The alloy liquid is kept at 750 ℃ for 10 min. The alloy liquid is fully stirred again for 3 min, and then kept at 710 ℃ for 10 min. After the slag is removed, the alloy liquid is poured under the protection of a protective gas.

[0034] The prepared ingot blank is subjected to homogenization treatment in a resistance furnace at 415 ℃ for 12 h. The homogenized ingot blank is subjected to surface turning, and the turned ingot blank is placed into a heating furnace and heated to 300 ℃ for 1 h. The ingot blank is placed into a reverse extrusion machine for extrusion. The temperature of the extrusion cylinder is 300 ℃, the extrusion ratio is 16:1, and the extrusion speed is 1 mm / s.

[0035] The rod prepared in the above process is processed into a standard tensile specimen according to the national standard, and the tensile property test is performed on an Instron 8032 tensile machine.

[0036] The tensile properties of the alloy obtained in this embodiment are as follows: the tensile tensile strength at room temperature is 333 MPa, the yield strength is 276 MPa, the elongation at room temperature is 25%, the compressive strength during compression is 520 MPa, the yield strength is 273 MPa, and the tensile-to-compressive yield ratio is 1.01. Example 2

[0037] In this embodiment, the mass percentages of the components in the alloy are as follows: Zn 8%, Dy 1.5%, Gd 1.5%, Pr 0.5%, Bi 0.1%, Sn 0.15% and Zr 0.4%, the atomic ratio of Dy / Gd is 1, the atomic ratio of Zn / (Gd and Dy) is 6.5, the total amount of impurity elements Si, Fe and Ni is 0.02%, and the balance is Mg. The preparation method of the alloy comprises the following steps:

[0038] The total amount of 2 Kg of corresponding metal ingots and master alloys corresponding to the above ingredients is weighed, and the oxide scales on the surfaces of all raw materials are polished off by sandpaper. Then, the weighed metal ingredients are placed in an oven at a temperature of 150 ℃ for 2 h of preheating. First, the preheated pure Mg, pure Dy, pure Pr, and Mg-30% Gd master alloy are placed in a melting furnace preheated to 690 ℃ for melting. During the melting process, a covering agent needs to be added. After the above raw materials are melted, the alloy liquid is manually stirred for 2 min to remove the slag on the surface of the alloy liquid and to protect it by spreading the covering agent on its surface. Then, the alloy liquid in the smelting furnace is heated to 790 ℃, and the Mg-30% Zr master alloy is added at one time. After the master alloy is completely melted, it is fully stirred. The temperature of the alloy liquid is reduced to 730 ℃, and the pure Zn, pure Bi, and pure Sn master alloy is added. After it is completely melted, the melt is fully stirred for 3 min, a layer of covering agent is spread, and the lid is closed. The alloy liquid is again fully stirred for 3 min, and then it is kept at 700 ℃ for 15 min. After removing the slag, the alloy liquid is poured under a protective gas.

[0039] The prepared ingot blank is subjected to homogenization treatment in a resistance furnace at 420 ℃ for 12 h. The homogenized ingot blank is surface turned, and the turned ingot blank is heated to 300 ℃ in a heating furnace for 1 h, and then it is put into a reverse extrusion machine for extrusion. The temperature of the extrusion cylinder is 300 ℃, the extrusion ratio is 16:1, and the extrusion speed is 1 mm / s.

[0040] The rod prepared in the above process is processed into a standard tensile specimen according to the national standard, and the tensile property test is performed on an Instron 8032 tensile machine.

[0041] The tensile properties of the alloy obtained in this embodiment are as follows: the tensile tensile strength at room temperature is 321 MPa, the yield strength is 266 MPa, the room temperature elongation is 26%, the compressive strength during compression is 503 MPa, the yield strength is 267 MPa, and the tensile-to-compressive yield ratio is 1. Example 3

[0042] In this embodiment, the components and their mass percentages in the alloy are as follows: Zn 9%, Dy 1.5%, Gd 1.5%, Pr 0.4%, Bi 0.15%, Sn 0.1%, and Zr 0.5%, the Dy / Gd atomic ratio is 1, the Zn / (Gd and Dy) atomic ratio is 7.2, the total amount of impurity elements Si, Fe, and Ni is 0.03%, and the balance is Mg. The preparation method of the alloy includes the following steps:

[0043] The total amount of 3 Kg of corresponding metal ingot and master alloy is weighed according to the above ingredients, the oxide skin on the surface of all raw materials is polished off by sandpaper, and then the weighed metal ingot and master alloy are put into an oven at a temperature of 150 ℃ for 2 h of preheating; first, the preheated pure Mg, pure Dy and pure Pr, and Mg-30% Gd master alloy are put into a melting furnace preheated to 700 ℃ for melting, and a covering agent needs to be added during the melting process; after the above raw materials are melted, the alloy liquid is manually stirred for 2 min, the slag on the surface of the alloy liquid is removed and the covering agent is scattered on the surface to protect it; then the alloy liquid in the smelting furnace is heated to 780 ℃, and the Mg-30% Zr master alloy is added at one time, and after the master alloy is completely melted, it is fully stirred; the temperature of the alloy liquid is reduced to 720 ℃, and the pure Zn, pure Bi and pure Sn master alloy is added, and after it is completely melted, the melt is fully stirred for 3 min, a layer of covering agent is scattered, and the lid is covered, and the temperature is kept at 750 ℃ for 10 min; the alloy melt is fully stirred again for 3 min, and then kept at 710 ℃ for 10 min after removing the slag, and then poured under the protection of protective gas.

[0044] The prepared ingot blank is subjected to homogenization treatment in a resistance furnace at 415 ℃ for 12 h; the homogenized ingot blank is surface turned, and the turned ingot blank is put into a heating furnace and heated to 300 ℃ for 1 h, and then put into a reverse extrusion machine for extrusion, with the extrusion cylinder temperature being 300 ℃, the extrusion ratio being 16:1, and the extrusion speed being 1 mm / s.

[0045] The rod prepared in the above process is processed into a standard tensile specimen according to the national standard, and the tensile property test is performed on an Instron 8032 tensile machine.

[0046] The tensile properties of the alloy obtained in this embodiment are as follows: the tensile tensile strength at room temperature is 349 MPa, the yield strength is 297 MPa, the room temperature elongation is 23%, the compressive strength during compression is 600 MPa, the yield strength is 301 MPa, and the tensile-to-compressive yield ratio is 0.98. Example 4

[0047] In this embodiment, the mass percentages of each component in the alloy are as follows: Zn 8.5%, Dy 1.2%, Gd 1.3%, Pr 0.5%, Bi 0.1%, Sn 0.1%, and Zr 0.5%, the Dy / Gd atomic ratio is 0.9, the Zn / (Gd and Dy) atomic ratio is 8.2, and the total amount of impurity elements Si, Fe and Ni is 0.03%, and the balance is Mg. The preparation method of the alloy comprises the following steps:

[0048] The total amount of 2 Kg of the corresponding metal ingot and master alloy is weighed according to the above ingredients, and the oxide scale on the surface of all raw materials is polished off by sandpaper, and then the weighed metal ingredients are placed in an oven at a temperature of 150 ℃ for 2 h of preheating; first, the preheated pure Mg, pure Dy and pure Pr, and Mg-30% Gd master alloy are placed in a melting furnace preheated to 690 ℃ for melting, and a covering agent needs to be added during the melting process. After the above raw materials are melted, the alloy liquid is manually stirred for 2 min to remove the slag on the surface of the alloy liquid and sprinkle a layer of covering agent on the surface for protection; then the alloy liquid in the smelting furnace is heated to 790 ℃, and the Mg-30% Zr master alloy is added at one time, and after the master alloy is completely melted, it is fully stirred; the temperature of the alloy liquid is reduced to 730 ℃, and the pure Zn, pure Bi and pure Sn master alloy is added, and after it is completely melted, the melt is fully stirred for 3 min, a layer of covering agent is sprinkled, and the lid is covered. After 15 min of heat preservation at 740 ℃, the alloy melt is fully stirred again for 3 min, and then after 15 min of heat preservation at 700 ℃, the slag is removed and the pouring is carried out under a protective gas.

[0049] The prepared ingot blank is subjected to homogenization treatment in a resistance furnace at 420 ℃ for 12 h; the homogenized ingot blank is surface turned, and the turned ingot blank is placed in a heating furnace and heated to 300 ℃ for 1 h, then placed in a reverse extrusion machine for extrusion, with the extrusion cylinder temperature being 300 ℃, the extrusion ratio being 16:1, and the extrusion speed being 1 mm / s.

[0050] The rod prepared by the above process is processed into a standard tensile specimen according to the national standard, and the tensile property test is carried out on an Instron 8032 tensile machine.

[0051] The tensile properties of the alloy obtained in this embodiment are as follows: the tensile tensile strength at room temperature is 337 MPa, the room temperature yield strength is 281 MPa, the room temperature elongation is 23.9%, the tensile-compressive yield ratio is 0.99, the compressive strength during compression is 545 MPa, the yield strength is 288 MPa, and the tensile-compressive yield ratio is 0.98. Example 5

[0052] In this embodiment, the mass percentages of the components in the alloy are as follows: Zn 7%, Dy 0.9%, Gd 1.2%, Pr 0.4%, Bi 0.2%, Sn 0.15%, and Zr 0.6%, the Dy / Gd atomic ratio is 0.8, the Zn / (Gd and Dy) atomic ratio is 8, the total amount of impurity elements Si, Fe and Ni is 0.03%, and the balance is Mg. The preparation method of the alloy comprises the following steps:

[0053] The total amount of 3 Kg of corresponding metal ingots and master alloys is weighed according to the above ingredients, and the oxide scales on the surfaces of all raw materials are polished off by sandpaper. Then the weighed metal ingots and master alloys are placed in an oven at 150 ℃ for 2 h of preheating. The preheated pure Mg, pure Dy, pure Pr and Mg-30% Gd master alloy are first placed in a melting furnace preheated to 700 ℃ for melting. Covering agent needs to be added during the melting process. After the above raw materials are melted, the alloy liquid is manually stirred for 2 min to remove the slag on the surface of the alloy liquid and sprinkle covering agent on the surface for protection. Then the alloy liquid in the smelting furnace is heated to 780 ℃, and the Mg-30% Zr master alloy is added at one time. After the master alloy is completely melted, it is fully stirred. The temperature of the alloy liquid is reduced to 720 ℃, and the pure Zn, pure Bi and pure Sn master alloy is added. After it is completely melted, the melt is fully stirred for 3 min, a layer of covering agent is sprinkled, and the lid is covered. The alloy melt is stirred again for 3 min at 710 ℃, and then placed for 10 min after removing the slag. Then the alloy melt is poured under the protection of protective gas.

[0054] The prepared ingot blank is subjected to homogenization treatment in a resistance furnace at 415 ℃ for 12 h. The homogenized ingot blank is surface turned, and the turned ingot blank is heated to 300 ℃ in a heating furnace for 1 h, and then put into a reverse extrusion machine for extrusion. The extrusion cylinder temperature is 300 ℃, the extrusion ratio is 16:1, and the extrusion speed is 1 mm / s.

[0055] The rod prepared by the above process is processed into a standard tensile specimen according to the national standard, and the tensile property test is performed on an Instron 8032 tensile machine.

[0056] The tensile properties of the alloy obtained in this example are as follows: the tensile tensile strength at room temperature is 344 MPa, the room temperature yield strength is 280 MPa, and the room temperature elongation is 24%; the compressive strength during compression is 562 MPa, the yield strength is 271 MPa; and the tensile-to-compressive yield ratio is 1.03.

Claims

1. A high-performance magnesium alloy having a tension-compression yield symmetry, characterized by, The alloy comprises the following components and their mass percentages: Zn 7.0-9.0%, Dy 0.5-1.5%, Gd 0.5-1.5%, Zr 0.3-0.6%, Pr 0.1-0.5%, Bi 0.05-0.20%, Sn 0.05-0.15%, and the total amount of impurity elements Si, Fe, Cu and Ni is less than 0.03%, and the balance is Mg; The mechanical property indexes of the high-performance magnesium alloy with tensile-compressive yield symmetry are as follows: for tensile test, the ultimate tensile strength at room temperature is 320-350 MPa, the yield strength at room temperature is 260-300 MPa, and the elongation at room temperature is greater than 23%; for compression test, the ultimate compressive strength at room temperature is 400-600 MPa, and the compressive yield strength at room temperature is 250-300 MPa; the tensile-compressive yield ratio of the alloy is 0.9-1.

1.

2. The high-performance magnesium alloy having tension-compression yield symmetry according to claim 1, characterized in that, The atomic ratio of Dy / Gd is 0.5-1, and the atomic ratio of Zn / (Gd and Dy) is 3.5-8.

5.

3. The high-performance magnesium alloy with symmetrical tensile-compressive yield strength according to any one of claims 1-2, characterized in that, The alloy comprises the following components and their mass percentages: Zn 7%, Dy 1%, Gd 1.5%, Pr 0.3%, Bi 0.05%, Sn 0.1% and Zr 0.5%, the total amount of impurity elements Si, Fe and Ni is less than 0.03%, and the balance is Mg.

4. The high-performance magnesium alloy with symmetrical tensile-compressive yield strength according to any one of claims 1-2, characterized in that, The alloy comprises the following components and their mass percentages: Zn 8%, Dy 1.5%, Gd 1.5%, Pr 0.5%, Bi 0.1%, Sn 0.15% and Zr 0.4%, the total amount of impurity elements Si, Fe and Ni is less than 0.03%, and the balance is Mg.

5. The high-performance magnesium alloy with symmetrical tensile and compressive yield strengths according to any one of claims 1-2, characterized in that, The alloy comprises the following components and their mass percentages: Zn 9%, Dy 1.5%, Gd 1.5%, Pr 0.4%, Bi 0.1%, Sn 0.1% and Zr 0.5%, the total amount of impurity elements Si, Fe and Ni is less than 0.03%, and the balance is Mg.

6. The method for preparing a high-performance magnesium alloy with tensile and compressive yield symmetry according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: (1) pure Mg, pure Zn, pure Dy, Mg-30% Gd intermediate alloy, pure Pr, pure Bi, pure Sn and Mg-30% Zr intermediate alloy are proportioned according to the component proportioning, and the oxide scales on the surfaces of all raw materials are polished off by sandpaper; (2) all raw materials are respectively placed in an oven for preheating before melting, the preheating temperature is 100-150 ℃, and the preheating time is 2-3 h; (3) the melting furnace is heated to 700-750 ℃, the preheated pure Mg, pure Dy, pure Pr and Mg-30% Gd intermediate alloy are placed in a crucible, a covering agent is sprinkled thereon, and the crucible cover is covered; after the above raw materials are completely melted, the crucible cover is opened, the slag on the surface of the alloy liquid is removed, the molten liquid is manually stirred for 1-4 min to uniformly mix, and then a layer of covering agent is sprinkled thereon and the cover is covered again; (4) After continuously heating to 780~800℃, Mg-30%Zr master alloy is added, and after the master alloy is completely melted, a proper amount of covering agent is scattered while stirring; the temperature of the alloy melt is reduced to 700~720℃, pure Zn, pure Bi and pure Sn are added, and after they are completely melted, the melt is stirred for 1~3 min, then a layer of covering agent is scattered, the lid is covered, and the temperature is kept at 700~750℃ for 10~20 min; the melt is stirred again for 1~3 min, then the temperature is kept at 690~710℃ for 10~20 min, after the slag is removed, casting is carried out; before casting, the slag on the surface of the melt is removed, and the casting process is carried out under a protective gas; (5) The ingot obtained after casting in step (4) is put into a resistance heating furnace for homogenization treatment, and the homogenization treatment system is: keeping at 400~450 ℃ for 10~15 h; (6) The ingot after homogenization in step (5) is surface turned to match the inner diameter and length of the extrusion cylinder of the extruder; the processed ingot is put into a heating furnace and heated to 250~300 ℃, and kept for 1~2 h; (7) The ingot after heating in step (6) is put into a preheated extrusion cylinder for extrusion, the extrusion speed is 1.0~5.0 mm / s, the preheating temperature of the extrusion cylinder is 250~300 ℃, and the extrusion ratio is 10~20:

1.

7. The method of claim 6, wherein the high-performance magnesium alloy having a symmetrical tensile-compressive yield strength is prepared by the steps of: preparing a magnesium alloy by mixing a magnesium alloy powder with a magnesium alloy powder having a different composition; and performing a hot extrusion process on the magnesium alloy. The protective gas in step (4) is SF6+CO2+air mixed gas, and the volume ratio of SF6:CO2:air is 0.5:40:50.

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