A micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy and its preparation method

Abstract

The present invention provides a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy, and the mass percentage content of each component is as follows: yttrium 5-11 wt.%, TiB₂ 0.3-0.9 wt.%, Al₂Y 1.85-5.56 wt.%, and the balance is magnesium. The present invention also provides a preparation method of the micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy. By adding a nano-TiB₂ / Al master alloy, while introducing nano-TiB₂ particles into the Mg-Y series alloy, the in-situ micron-sized Al₂Y particles with good thermal stability are formed by the reaction of Al element and Y element; the micron-sized Al₂Y particles and nano-TiB₂ particles can be used as heterogeneous nucleation sites of α-Mg to refine the alloy structure, improve the distribution of the Mg-Y phase, and play a role of second-phase strengthening, significantly improving the room-temperature and high-temperature mechanical properties of the Mg-Y alloy, especially the high-temperature yield strength and high-temperature tensile strength at 300-350 °C. The preparation method of the present invention has a simple process and is beneficial to expanding the application of magnesium alloys in key components in the fields of aerospace and national defense.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat-resistant magnesium alloys, and particularly relates to a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy and a preparation method thereof. Background Art

[0002] Magnesium alloys are applied in the fields of automobiles, aerospace, and electronics due to their advantages such as low density, high specific strength, and excellent damping performance. However, the high-temperature strength of magnesium alloys is low, and the high-temperature creep resistance is poor, which greatly limits their application as lightweight structural materials in the fields of aerospace and national defense. Some studies have used ceramic particles to enhance the properties of magnesium alloy materials. However, in the process of preparing ceramic particle-reinforced magnesium matrix composites, technical problems such as poor wettability between the externally added ceramic particles and the magnesium matrix and easy contamination of the ceramic particle surface often occur, resulting in problems such as agglomeration of ceramic particles and poor interfacial bonding strength between the ceramic particles and the magnesium matrix in the prepared composites.

[0003] Mg-Y series rare earth alloys have strong solid solution strengthening and precipitation strengthening effects, and the formed second phase can improve the mechanical properties of magnesium alloys at room temperature and high temperature. However, it still urgently needs to solve important problems such as high cost of rare earth elements and low strength and toughness of the alloy. In addition, with the increase in temperature, especially at high temperatures (≥300 °C), the second phase in the Mg-Y series alloy will coarsen, grow, or dissolve, resulting in a significant decrease in strength and inability to safely serve for a long time at high temperatures. Therefore, exploring how to introduce a second phase with high high-temperature stability into the Mg-Y series rare earth magnesium alloy to further improve the high-temperature stability of the alloy structure and high-temperature mechanical properties has important theoretical guiding significance and engineering application value for the development and application of high-strength heat-resistant magnesium alloys. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy and a preparation method thereof in view of the deficiencies of the above-mentioned prior art. By adding a nano-TiB2 / Al master alloy, nano-TiB2 ceramic particles are introduced into the magnesium matrix, and in-situ micron-sized Al2Y particles are generated at the same time. Both the micron-sized Al2Y particles and the nano-TiB2 particles can be used as heterogeneous nucleation sites for α-Mg to refine the alloy structure, improve the distribution of the Mg-Y phase, and play a role in second-phase strengthening, thereby improving the mechanical properties of the alloy and being beneficial to further expanding the application of magnesium rare earth alloys as key components in the fields of aerospace and national defense.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy, and the mass percentage content of each component in the micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy is: yttrium 5-11 wt.%, TiB₂ 0.3-0.9 wt.%, Al₂Y 1.85-5.56 wt.%, and the balance is magnesium.

[0006] A preparation method of the micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy, and the method includes the following steps:

[0007] S1. Raw material grinding: Take raw materials of pure magnesium, Mg-Y master alloy and TiB₂ / Al master alloy, and grind the raw materials clean to remove surface stains and oxide skins.

[0008] S2. Alloy melting: First, melt pure magnesium in a resistance furnace under the protection of a mixed gas; then add Mg-Y master alloy and TiB₂ / Al master alloy respectively, melt, keep warm for 15-20 min, stir to remove slag, and finally cast to obtain an ingot.

[0009] S3. Homogenization treatment: Perform homogenization treatment on the ingot obtained in S2, and air-cool the treated ingot to room temperature to obtain a billet.

[0010] S4. Extrusion treatment: Perform hot extrusion on the billet obtained in S3 to obtain an extruded bar, which is the micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy.

[0011] Preferably, the purity of the pure magnesium in S1 is 99.8%; the Mg-Y master alloy is Mg-25 wt.% Y with a purity of 99.9%; the mass ratio of TiB₂ to Al in the TiB₂ / Al master alloy is 30:70, and the average size of TiB₂ particles is 98 nm.

[0012] Preferably, the dosages of the pure magnesium, Mg-Y master alloy and TiB₂ / Al master alloy in S1 are:

[0013] When the mass ratio of yttrium content in pure magnesium and Mg-Y master alloy and the mass ratio of TiB₂ / Al master alloy is (94, 92, 90, 88):(5, 7, 9, 11):1, the obtained micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy is (0.3 wt.% TiB₂ + 1.85 wt.% Al₂Y) / Mg-(5, 7, 9, 11)Y;

[0014] When the yttrium content in pure magnesium and magnesium-yttrium master alloy and the mass ratio of TiB2 / Al master alloy are (93, 91, 89, 87):(5, 7, 9, 11):2, the obtained micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy is (0.6wt.% TiB2 + 3.71wt.% Al2Y) / Mg-(5, 7, 9, 11)Y;

[0015] When the yttrium content in pure magnesium and magnesium-yttrium master alloy and the mass ratio of TiB2 / Al master alloy are (92, 90, 88, 86):(5, 7, 9, 11):3, the obtained micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy is (0.9wt.% TiB2 + 5.56wt.% Al2Y) / Mg-(5, 7, 9, 11)Y.

[0016] Preferably, the mixed protective gas in S2 is composed of CO2 with a volume fraction of 99% and SF6 with a volume fraction of 1%.

[0017] Preferably, the melting temperature of the pure magnesium in S2 is 710-730°C; the melting temperatures of the pure magnesium, magnesium-yttrium master alloy and TiB2 / Al master alloy are 700-750°C; the casting temperature is 700-710°C.

[0018] Preferably, the diameter of the ingot in S2 is 85 mm.

[0019] Preferably, the temperature of the homogenization treatment in S3 is 500°C and the time is 12 h.

[0020] Preferably, the hot extrusion temperature in S4 is 440°C and the extrusion ratio is 18:1;

[0021] Preferably, the diameter of the extruded bar in S4 is 20 mm.

[0022] Preferably, the micro-nano dual-scale particles in S4 are TiB2 nano-particles and Al2Y micro-particles respectively, where the diameter of the TiB2 nano-particles is 86-105 nm and the diameter of the Al2Y micro-particles is 8.6-59.3 μm; the high-temperature yield strength of the prepared micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy at 300-350°C is 171-274 MPa, and the high-temperature tensile strength is 192-322 MPa.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention provides a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy and a preparation method thereof. The nano-TiB2 particles and micron-Al2Y particles significantly improve the room-temperature and high-temperature mechanical properties of the Mg-Y alloy, especially the high-temperature yield strength and high-temperature tensile strength at 300-350 °C, and expand the application of magnesium alloys as key components in the aerospace and defense fields.

[0025] 2. By adding a nano-TiB2 / Al master alloy, the present invention introduces nano-TiB2 particles into the Mg-Y series alloy, and at the same time, the Al element reacts with the Y element to generate in-situ micron-Al2Y particles with good thermal stability. The introduced nano-TiB2 particles have a clean interface with the Mg matrix without inclusions and a high lattice matching degree with the magnesium matrix, which plays a role in refining the α-Mg grains. At the same time, they can act as high-melting-point hard second phases to pin the dislocation movement and grain boundary sliding, improving the thermal stability of the microstructure; the Al2Y particles, as heterogeneous nucleation sites, refine the alloy microstructure while improving the distribution of the Mg-Y phase, thus significantly improving the high-temperature mechanical properties of the magnesium alloy.

[0026] 3. During the melting and preparation process of the present invention, a well-dispersed nano-TiB2-micron-Al2Y co-reinforced Mg-Y series alloy material can be obtained without using additional means such as mechanical stirring and ultrasonic dispersion. The preparation process is simple, easy to promote, and has good application prospects.

[0027] The following further elaborates the present invention in detail with reference to the drawings and embodiments. Description of the Drawings

[0028] Figure 1 It is a scanning electron microscope image of different content (TiB2-Al2Y) / Mg-9Y composite materials prepared in Examples 4-6 of the present invention and the Mg-9Y matrix alloy prepared in Comparative Example 2; among them, a is the scanning electron microscope image of the Mg-9Y alloy, b is the scanning electron microscope image of the extruded state (0.3 wt.% TiB2-1.85 wt.% Al2Y) / Mg-9Y alloy in Example 4, c is the scanning electron microscope image of the extruded state (0.6 wt.% TiB2-3.71 wt.% Al2Y) / Mg-9Y alloy in Example 5, and d is the scanning electron microscope image of the extruded state (0.9 wt.% TiB2-5.56 wt.% Al2Y) / Mg-9Y alloy in Example 6.

[0029] Figure 2 It is the tensile engineering stress-strain curve of (0.6 wt.% TiB2-3.71 wt.% Al2Y) / Mg-llY prepared in Example 2 of the present invention at 250-350 °C.

[0030] Figure 3Engineering stress-strain curves of (0.6wt.%TiB2-3.71wt.%Al2Y) / Mg-9Y prepared in Example 5 at 250 - 350 °C.

[0031] Figure 4 Engineering stress-strain curves of (0.6wt.%TiB2-3.71wt.%Al2Y) / Mg-7Y prepared in Example 7 at 250 - 350 °C.

[0032] Figure 5 Engineering stress-strain curves of (0.6wt.%TiB2-3.71wt.%Al2Y) / Mg-5Y prepared in Example 8 at 250 - 350 °C. Detailed implementation manners

[0033] Example 1

[0034] This example is a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy, and the mass percentage content of each component is: 11wt.% yttrium, 0.3wt.% TiB2, 1.85wt.% Al2Y, and the balance is magnesium.

[0035] A preparation method of a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy, comprising the following steps:

[0036] S1. Raw material grinding: Take pure magnesium, Mg-Y master alloy and TiB2 / Al master alloy raw materials, and grind the raw materials clean to remove surface stains and oxide scales;

[0037] The mass ratio of pure magnesium, yttrium content in the Mg-Y master alloy, and the TiB2 / Al master alloy in the raw materials is 88:11:1;

[0038] The purity of the pure magnesium is 99.8%;

[0039] The Mg-Y master alloy is Mg-25wt.%Y with a purity of 99.9%, purchased from Chongqing Yuhua New Materials Technology Co., Ltd.;

[0040] The preparation method of the TiB2 / Al master alloy is: TiB2 and pure aluminum powder with a mass ratio of 30:70 are ball-milled and then hot-pressed and sintered to prepare a 30wt.% TiB2 / Al master alloy; the ball-milling speed is 100r / min; the ball-to-material ratio is 3:1; the hot-pressing and sintering temperature is 650 °C; among them, TiB2 is purchased from Shanghai Xiangtian Nano Materials Co., Ltd., with a size of 86 - 105nm (average size of 98nm); pure aluminum powder is purchased from Beijing Xingrongyuan Technology Co., Ltd., with a size of 9 - 13μm (average size of 10μm) and a purity of 99.5%;

[0041] S2. Alloy Melting: Under the protection of 99% CO2 - 1% SF6 mixed gas, first melt pure magnesium in a resistance furnace at 710 - 730 °C, then add magnesium-yttrium master alloy and TiB2 / Al master alloy respectively, melt at 700 - 750 °C, keep warm for 15 - 20 min, stir to remove slag, and finally cast to obtain an ingot with a diameter of 85 mm;

[0042] S3. Homogenization Treatment: Homogenize the ingot obtained in S2. The homogenization temperature is 500 °C and the time is 12 h. After treatment, the ingot is air-cooled to room temperature to obtain a billet;

[0043] S4. Extrusion Treatment: Hot-extrude the billet obtained in S3 at 440 °C, with an extrusion ratio of 18:1, and finally obtain an extrusion bar with a diameter of 20 mm, which is the micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy (0.3 wt.% TiB2 - 1.85 wt.% Al2Y) / Mg-11Y.

[0044] Example 2

[0045] This example is a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy. The mass percentage content of each component is: yttrium 11 wt.%, TiB2 0.6 wt.%, Al2Y 3.71 wt.%, and the balance is magnesium; that is, the mass ratio of pure magnesium, yttrium content in magnesium-yttrium master alloy, and TiB2 / Al master alloy in the raw materials is 87:11:2. The preparation method is the same as that in Example 1, and finally the alloy material obtained is (0.6 wt.% TiB2 - 3.71 wt.% Al2Y) / Mg-11Y.

[0046] Example 3

[0047] This example is a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy. The mass percentage content of each component is: yttrium 11 wt.%, TiB2 0.9 wt.%, Al2Y 5.56 wt.%, and the balance is magnesium; that is, the mass ratio of pure magnesium, yttrium content in magnesium-yttrium master alloy, and TiB2 / Al master alloy in the raw materials is 86:11:3. The preparation method is the same as that in Example 1, and finally the alloy material obtained is (0.9 wt.% TiB2 - 5.56 wt.% Al2Y) / Mg-11Y.

[0048] Example 4

[0049] This example is a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy. The mass percentage content of each component is as follows: yttrium 9 wt.%, TiB₂ 0.3 wt.%, Al₂Y 1.85 wt.%, and the balance is magnesium; that is, the mass ratio of pure magnesium, yttrium content in the magnesium-yttrium master alloy, and the TiB₂ / Al master alloy in the raw materials is 90:9:1. The preparation method is the same as that of Example 1, and the final alloy material obtained is (0.3 wt.% TiB₂ - 1.85 wt.% Al₂Y) / Mg-9Y.

[0050] Example 5

[0051] This example is a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy. The mass percentage content of each component is as follows: yttrium 9 wt.%, TiB₂ 0.6 wt.%, Al₂Y 3.71 wt.%, and the balance is magnesium; that is, the mass ratio of pure magnesium, yttrium content in the magnesium-yttrium master alloy, and the TiB₂ / Al master alloy in the raw materials is 89:9:2. The preparation method is the same as that of Example 1, and the final alloy material obtained is (0.6 wt.% TiB₂ - 3.71 wt.% Al₂Y) / Mg-9Y.

[0052] Example 6

[0053] This example is a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy. The mass percentage content of each component is as follows: yttrium 9 wt.%, TiB₂ 0.9 wt.%, Al₂Y 5.56 wt.%, and the balance is magnesium; that is, the mass ratio of pure magnesium, yttrium content in the magnesium-yttrium master alloy, and the TiB₂ / Al master alloy in the raw materials is 88:9:3. The preparation method is the same as that of Example 1, and the final alloy material obtained is (0.9 wt.% TiB₂ - 5.56 wt.% Al₂Y) / Mg-9Y.

[0054] Example 7

[0055] This example is a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy. The mass percentage content of each component is as follows: yttrium 7 wt.%, TiB₂ 0.6 wt.%, Al₂Y 3.71 wt.%, and the balance is magnesium; that is, the mass ratio of pure magnesium, yttrium content in the magnesium-yttrium master alloy, and the TiB₂ / Al master alloy in the raw materials is 91:7:2. The preparation method is the same as that of Example 1, and the final alloy material obtained is (0.6 wt.% TiB₂ - 3.71 wt.% Al₂Y) / Mg-7Y.

[0056] Example 8

[0057] This embodiment is a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy. The mass percentage content of each component is as follows: yttrium 5 wt.%, TiB₂ 0.6 wt.%, Al₂Y 3.71 wt.%, and the balance is magnesium; that is, the mass ratio of pure magnesium, yttrium content in the magnesium-yttrium master alloy, and the TiB₂ / Al master alloy in the raw materials is 93:5:2. The preparation method is the same as that of Example 1, and the final alloy material obtained is (0.6 wt.% TiB₂ - 3.71 wt.% Al₂Y) / Mg-5Y.

[0058] Comparative Example 1

[0059] The mass percentage of each raw material component is as follows: yttrium 11 wt.%, and the balance is magnesium. The preparation method is the same as that of Example 1, and the Mg-11Y matrix alloy is obtained.

[0060] Comparative Example 2

[0061] The mass percentage of each raw material component is as follows: yttrium 9 wt.%, and the balance is magnesium. The preparation method is the same as that of Example 1, and the Mg-9Y matrix alloy is obtained.

[0062] Comparative Example 3

[0063] The mass percentage of each raw material component is as follows: yttrium 7 wt.%, and the balance is magnesium. The preparation method is the same as that of Example 1, and the Mg-7Y matrix alloy is obtained.

[0064] Comparative Example 4

[0065] The mass percentage of each raw material component is as follows: yttrium 5 wt.%, and the balance is magnesium. The preparation method is the same as that of Example 1, and the Mg-5Y matrix alloy is obtained.

[0066] The micro-nano dual-scale particles in the micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy prepared by the present invention are TiB₂ nano-particles and Al₂Y micro-particles respectively. The diameter of the TiB₂ nano-particles is 86 - 105 nm, and the diameter of the Al₂Y micro-particles is 8.6 - 59.3 μm.

[0067] The structures and properties of the alloys prepared in Examples 1 - 8 and Comparative Examples 1 - 4 are analyzed as follows:

[0068] 1. As-cast microstructure analysis

[0069] The as-cast structure is the microstructure formed after the alloy material transforms from the molten metal to a solid (casting) during the smelting process. The as-cast structure of the Mg-11Y matrix alloy in Comparative Example 1 is mainly dendritic, and the grain size of α-Mg is 132 - 690 μm; after introducing nano-TiB2 + micron Al2Y particles into the alloy, the alloy structure is mainly equiaxed grains. The average grain size of α-Mg in the as-cast (0.3 wt.% TiB2 + 1.85 wt.% Al2Y) / Mg-11Y alloy in Example 1 is 38.5 μm; the average grain size of α-Mg in the as-cast (0.6 wt.% TiB2 + 3.71 wt.% Al2Y) / Mg-11Y alloy in Example 2 is 26.2 μm; the average grain size of α-Mg in the as-cast (0.9 wt.% TiB2 + 5.56 wt.% Al2Y) / Mg-11Y alloy in Example 3 is 19.9 μm. It shows that nano-TiB2 + micron Al2Y particles can significantly refine the as-cast structure of the Mg-Y alloy.

[0070] 2. Microstructure analysis

[0071] Figure 1 The SEM images of the Mg-9Y matrix alloy and (TiB2 - Al2Y) / Mg-9Y composites with different contents prepared in Examples 4 - 6 and Comparative Example 2 of the present invention are shown. a is the SEM image of the Mg-9Y matrix alloy, b is the SEM image of the extruded (0.3 wt.% TiB2 - 1.85 wt.% Al2Y) / Mg-9Y alloy in Example 4, c is the SEM image of the extruded (0.6 wt.% TiB2 - 3.71 wt.% Al2Y) / Mg-9Y alloy in Example 5, and d is the SEM image of the extruded (0.9 wt.% TiB2 - 5.56 wt.% Al2Y) / Mg-9Y alloy in Example 6. It shows that with the introduction of nano-TiB2 and micron Al2Y particles, micron-scale particulate Al2Y phases can be observed in the alloy, and with the increase of the contents of TiB2 and Al2Y particles, the volume fraction of the second phase in the alloy gradually increases.

[0072] 3. Room temperature strength test

[0073] The room-temperature yield strength and tensile strength of the (0.3 wt.% TiB2 + 1.85 wt.% Al2Y) / Mg-11Y alloy of Example 1 were 273 MPa and 329 MPa, respectively, which were 39 MPa and 42 MPa higher than those of the Mg-11Y matrix alloy (234 MPa, 287 MPa) of Comparative Example 1. The room-temperature yield strength and tensile strength of the (0.6 wt.% TiB2 + 3.71 wt.% Al2Y) / Mg-9Y alloy of Example 5 were 269 MPa and 315 MPa, respectively, which were 39 MPa and 29 MPa higher than those of the Mg-9Y matrix alloy (230 MPa, 286 MPa) of Comparative Example 2. It shows that the nano-TiB2 + micro-Al2Y particles can significantly improve the room-temperature strength of the extruded Mg-Y alloy.

[0074] 4. High-temperature strength test

[0075] The high-temperature tensile properties of the extruded alloys obtained from Examples 1-8 and Comparative Examples 1-4 were tested at different temperatures, and the tensile yield strength, tensile strength, and fracture strain were statistically analyzed. The results are shown in Table 1.

[0076] Table 1 Performance test of the extruded alloy at different temperatures

[0077]

[0078]

[0079] Figure 2 The tensile engineering stress-strain curves of the (0.6 wt.% TiB2 - 3.71 wt.% Al2Y) / Mg-11Y prepared in Example 2 of the present invention at 250 °C, 300 °C, and 350 °C.

[0080] According to Table 1, by comparing the high-temperature tensile properties of Example 2 and Comparative Example 1 at different temperatures, it is obtained that after introducing nano-TiB2 and micro-Al2Y particles into the Mg-11Y alloy, the high-temperature strength of the alloy is significantly improved. The yield strength and tensile strength of the (0.6 wt.% TiB2 + 3.71 wt.% Al2Y) / Mg-11Y alloy of Example 2 at 300 °C were 274 MPa and 322 MPa, respectively, which were 66 MPa and 65 MPa higher than those of the Mg-11Y matrix alloy (208 MPa, 257 MPa); the yield strength and tensile strength at 350 °C were 246 MPa and 283 MPa, respectively, which were 33 MPa and 27 MPa higher than those of the Mg-11Y matrix alloy (213 MPa, 256 MPa).

[0081] Figure 3Engineering stress-strain curves of (0.6 wt.% TiB2 - 3.71 wt.% Al2Y) / Mg-9Y prepared for Example 5 at 250 °C, 300 °C and 350 °C.

[0082] According to Table 1, by comparing the high-temperature tensile properties of Examples 4 - 6 and Comparative Example 2 at different temperatures, it is obtained that the yield strength and tensile strength of the (0.3 wt.% TiB2 + 1.85 wt.% Al2Y) / Mg-9Y alloy in Example 4 at 300 °C are 237 MPa and 291 MPa respectively, which are 34 MPa and 36 MPa higher than those of the Mg-9Y matrix alloy (203 MPa, 255 MPa); the yield strength and tensile strength of the (0.6 wt.% TiB2 + 3.71 wt.% Al2Y) / Mg-9Y alloy in Example 5 at 350 °C are 213 MPa and 241 MPa respectively, which are 36 MPa and 17 MPa higher than those of the Mg-9Y matrix alloy (177 MPa, 224 MPa).

[0083] Figure 4 Engineering stress-strain curves of (0.6 wt.% TiB2 - 3.71 wt.% Al2Y) / Mg-7Y prepared for Example 7 at 250 - 350 °C. From Table 1, by comparing the high-temperature tensile properties of Example 7 and Comparative Example 3, the yield strength and tensile strength of the (0.6 wt.% TiB2 - 3.71 wt.% Al2Y) / Mg-7Y alloy at 350 °C are 193 MPa and 220 MPa respectively, which are 48 MPa and 31 MPa higher than those of the Mg-7Y matrix alloy (145 MPa, 189 MPa).

[0084] Figure 5 Engineering stress-strain curves of (0.6 wt.% TiB2 - 3.71 wt.% Al2Y) / Mg-5Y prepared for Example 8 at 250 - 350 °C. From Table 1, by comparing the high-temperature tensile properties of Example 8 and Comparative Example 4, the yield strength of the (0.6 wt.% TiB2 - 3.71 wt.% Al2Y) / Mg-5Y alloy at 350 °C is 171 MPa, which is 52 MPa higher than the yield strength of the Mg-5Y matrix alloy (119 MPa), indicating that the nano-TiB2 and micron-Al2Y particles effectively improve the high-temperature strength of the alloy.

[0085] In the present invention, nano-TiB2 particles are introduced into the magnesium alloy by means of a nano-TiB2 / Al master alloy. On the one hand, problems such as surface contamination, poor dispersion uniformity, and poor wettability of the nano-TiB2 particles are avoided. In the prepared composite material, the interface between the TiB2 particles and the α-Mg matrix is clean and continuous, and the lattice matching relationship is good, which can effectively strengthen the magnesium alloy. On the other hand, an in-situ reaction occurs between the Al element and the Y element to generate micron-sized Al2Y particles. Both the Al2Y particles and the TiB2 particles can serve as heterogeneous nucleation cores for α-Mg, playing a role in refining the matrix structure and improving the size and distribution of the second phase. The introduction of micro-nano TiB2-Al2Y particles refines the as-cast structure of the Mg-Y alloy and improves the room-temperature and high-temperature strength of the Mg-Y alloy by pinning dislocation movement and hindering grain boundary sliding.

[0086] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy, characterized in that, The micro-nano dual-scale particles are TiB2 nano-particles and Al2Y micro-particles respectively. The diameter of the TiB2 nano-particles is 86 - 105 nm, and the diameter of the Al2Y micro-particles is 8.6 - 59.3 μm. The mass percentage contents of the components in the micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy are as follows: yttrium 5 - 11 wt.%, TiB2 0.3 - 0.9 wt.%, Al2Y 1.85 - 5.56 wt.%, and the balance is magnesium. The preparation method is to introduce nano-TiB2 particles into the Mg-Y series alloy by adding a nano-TiB2 / Al master alloy, and in-situ micro-Al2Y particles are generated at the same time.

2. A preparation method of a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy as described in claim 1, characterized in that, This method includes the following steps: S1. Raw material grinding: Take pure magnesium, Mg-Y master alloy and TiB2 / Al master alloy raw materials, and grind the raw materials clean to remove surface stains and oxide scales. S2. Alloy melting: First, melt pure magnesium in a resistance furnace under a mixed gas protection; then add the Mg-Y master alloy and TiB2 / Al master alloy respectively, melt, keep warm for 15 - 20 min, stir to remove slag, and finally cast to obtain an ingot. S3. Homogenization treatment: Perform homogenization treatment on the ingot obtained in S2, and air-cool the treated ingot to room temperature to obtain a billet. S4. Extrusion treatment: Perform hot extrusion on the billet obtained in S3 to obtain an extruded bar, which is the micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy.

3. The preparation method of a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy according to claim 2, characterized in that The purity of the pure magnesium in S1 is 99.8%; the Mg-Y master alloy is Mg-25 wt.%Y with a purity of 99.9%; the mass ratio of TiB2 to Al in the TiB2 / Al master alloy is 30:70, and the average size of the TiB2 particles is 98 nm.

4. The preparation method of a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy according to claim 2, characterized in that, The dosages of the pure magnesium, Mg-Y master alloy and TiB2 / Al master alloy in S1 are as follows: When the mass ratio of pure magnesium, the yttrium content in the Mg-Y master alloy, and the TiB2 / Al master alloy is (94,92,90,88):(5,7,9,11):1, the obtained micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy is (0.3 wt.% TiB2 + 1.85 wt.%Al2Y) / Mg-(5,7,9,11)Y; When the mass ratio of pure magnesium, the yttrium content in the Mg-Y master alloy, and the TiB2 / Al master alloy is (93,91,89,87):(5,7,9,11):2, the obtained micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy is (0.6 wt.% TiB2 + 3.71 wt.%Al2Y) / Mg-(5,7,9,11)Y; When the mass ratio of pure magnesium, the yttrium content in the Mg-Y master alloy, and the TiB2 / Al master alloy is (92,90,88,86):(5,7,9,11):3, the obtained micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy is (0.9 wt.% TiB2 + 5. The preparation method of a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy according to claim 2, characterized in that, The mixed gas described in S2 is composed of CO2 with a volume fraction of 99% and SF6 with a volume fraction of 1%.

6. The preparation method of a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy according to claim 2, characterized in that, The melting temperature of the pure magnesium described in S2 is 710~730°C; the melting temperatures of the pure magnesium, magnesium-yttrium master alloy, and TiB2 / Al master alloy are 700~750°C; the casting temperature is 700~710°C; the diameter of the ingot is 85 mm.

7. A preparation method of a micro-nano dual-scale particle-reinforced Mg-Y series heat-resistant alloy according to claim 2, characterized in that, The temperature of the homogenization treatment described in S3 is 500°C and the time is 12 h.

8. A preparation method of a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy according to claim 2, characterized in that, The hot extrusion temperature described in S4 is 440°C and the extrusion ratio is 18:

1.

9. The preparation method of a micro-nano dual-scale particle reinforced Mg-Y series heat-resistant alloy according to claim 2, wherein, The diameter of the extruded bar described in S4 is 20 mm.

10. The preparation method of a micro-nano dual-scale particle-reinforced Mg-Y-based heat-resistant alloy according to claim 2, characterized in that, The high-temperature yield strength of the micro-nano dual-scale particle-reinforced Mg-Y-based heat-resistant alloy prepared in S4 at 300-350°C is 171~274 MPa, and the high-temperature tensile strength is 192~322 MPa.

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