High-toughness corrosion-resistant semi-solid injection molding magnesium alloy and preparation method thereof

Abstract

The invention discloses a high-toughness corrosion-resistant semi-solid injection molding magnesium alloy and a preparation method thereof, and belongs to the technical field of metal materials. The magnesium alloy comprises the following chemical components in percentage by weight: 8.6 to 11 percent of aluminum, 0.5 to 1 percent of zinc, 0.05 to 0.4 percent of manganese, 0.05 to 0.2 percent of calcium, 0.6 to 2 percent of rare earth element RE and the balance of magnesium and inevitable impurities. The preparation method of the alloy comprises the following steps: (1) adding raw materials according to the component proportion, smelting into magnesium alloy melt, pouring into a mold, and molding to obtain a magnesium alloy ingot; (2) cutting the cast ingot into magnesium alloy semi-solid blank particles; (3) performing injection molding to obtain a molded part; (4) solid solution heat treatment; and (5) performing two-stage aging heat treatment. The magnesium alloy has high toughness and corrosion resistance, and is suitable for semi-solid injection molding. The forming process can achieve near-net forming of complex components, and castings are few in defect, compact in structure and wide in application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal materials, in particular to a high-strength and high-toughness corrosion-resistant semi-solid injection molding magnesium alloy and a preparation method thereof. BACKGROUND

[0002] Semi-solid injection molding can realize near-net forming of complex magnesium alloy components. This process does not require melting and gas protection, and the density of the castings is high and the porosity is low. Therefore, compared with die-cast magnesium alloys, semi-solid magnesium alloys can realize heat treatment strengthening. In the fields of lightweight in new energy vehicles, low-altitude economy and national defense, semi-solid injection molding magnesium alloys have broad application prospects.

[0003] At present, there are few magnesium alloy composition systems suitable for semi-solid injection molding. The commonly used one is commercial AZ series alloy. However, the coarse eutectic Mg 17 Al 12 phase in the AZ series alloy leads to low mechanical properties of the alloy, which cannot meet the service requirements. In addition, the cathode Mg 17 Al 12 phase leads to rapid dissolution of the anode magnesium matrix, resulting in poor corrosion resistance of the alloy. Although conventional aging treatment can improve the strength of the AZ series semi-solid magnesium alloy, the coarse DP phase precipitated on the grain boundary during the aging process will proliferate rapidly, thereby significantly deteriorating the plasticity of the alloy, leading to difficulty in greatly improving the mechanical properties of the alloy. Therefore, the current commercial AZ series semi-solid injection molding magnesium alloy is faced with the bottleneck problems of low strength and toughness and poor corrosion resistance, which limits its further application. How to develop a new type of high-strength and high-toughness corrosion-resistant semi-solid injection molding magnesium alloy through alloy composition design and inhibit the coarsening of the DP phase during heat treatment and promote the precipitation of fine CP strengthening phase is a technical problem to be solved at present. SUMMARY

[0004] The purpose of the present application is to provide a high-strength and high-toughness corrosion-resistant semi-solid injection molding magnesium alloy and a preparation method thereof. By designing the composition of the magnesium alloy and the preparation process conditions, the strength, plasticity and corrosion resistance of the prepared magnesium alloy are all better than those of the existing commercial AZ91, AZ80 and other semi-solid magnesium alloys.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A high-strength and high-toughness corrosion-resistant semi-solid injection molding magnesium alloy, according to weight percentage, its chemical composition is: aluminum 8.6-11%, zinc 0.5-1%, manganese 0.05-0.4%, calcium 0.05-0.2%, rare earth element RE 0.6-2%, and the balance is magnesium and unavoidable impurities.

[0006] Further, the magnesium alloy chemical composition, aluminum preferably 9.5-10.5wt.%, zinc preferably 0.65-0.8wt.%, manganese preferably 0.1-0.25wt.%, calcium preferably 0.1-0.2wt.%, rare earth elements RE preferably 0.6-0.9%.

[0007] Further, the rare earth elements RE preferably one or more of cerium, neodymium, samarium and gadolinium.

[0008] Further, the magnesium alloy yield strength ≥200MPa, tensile strength ≥320MPa, elongation ≥10%, the average corrosion rate after immersion in 3.5wt.% NaCl solution for 14 days ≤0.15mm / y.

[0009] Further, the preparation method of the high-strength and high-toughness corrosion-resistant semi-solid injection molding magnesium alloy, comprising the following steps: (1) under inert gas protection, according to the component ratio, pure magnesium, pure aluminum, pure zinc and magnesium-manganese intermediate alloy are added in turn, heated and melted at 670-750℃; then magnesium-calcium intermediate alloy and magnesium-RE intermediate alloy (one or more of magnesium-cerium intermediate alloy, magnesium-neodymium intermediate alloy, magnesium-samarium intermediate alloy and magnesium-gadolinium intermediate alloy) are added in turn; stirred uniformly at 670-720℃, and then refined, degassed and deslagged to obtain a magnesium alloy melt, which is poured into a mold to form a magnesium alloy ingot; (2) the magnesium alloy ingot obtained in step (1) is cut into magnesium alloy semi-solid billet particles, which are rectangular columnar structure, and the particle size is 1-1.5mm in length, 1-1.5mm in width and 2-4mm in height; (3) the semi-solid billet particles obtained in step (2) are sent into an injection molding machine for injection molding to obtain a molded part; (4) the molded part obtained in step (3) is subjected to solid solution heat treatment under argon protection, and then water quenching is carried out to obtain a solid solution semi-solid molded part; (5) the solid solution semi-solid molded part obtained in step (4) is subjected to two-stage aging heat treatment to obtain the high-strength and high-toughness corrosion-resistant semi-solid injection molding magnesium alloy.

[0010] Further, in step (3), the injection molding process is as follows: the semi-solid billet particles are sent into the feeding hopper of the injection molding machine, and then into the metal sleeve; under the combined action of screw shearing and sleeve external heater, the particles are melted to the semi-solid interval; under the action of high-speed injection system, the semi-solid slurry is injected into the preheated mold cavity, and the molded part is obtained after cooling and solidification.

[0011] Further, in step (3), the solid phase fraction of the semi-solid interval is 20-55%; in the injection molding process, the injection temperature is 570-600℃, the injection speed is 2-5m / s, and the injection pressure is 70-100MPa.

[0012] Further, in step (4), the solid solution heat treatment temperature is 390-410℃, and the time is 1-3h.

[0013] Further, in step (5), the two-stage aging heat treatment is: first aging at 120-130℃ for 5-15h, and then aging at 150-170℃ for 5-25h.

[0014] The advantages and beneficial effects of the present application are as follows: 1. The commonly used semi-solid injection molding magnesium alloy is AZ series magnesium alloy, such as AZ91, and the Al content is usually ≤9.5%, and the Al content in the magnesium alloy of the present application can reach 11%. The semi-solid injection molding solidification cold speed is fast, so it is easy to form a supersaturated solid solution. Increasing the Al content to 11% can increase the Al solute atom content in the matrix. During the corrosion process, the Al atoms in the matrix are oxidized to Al2O3 and deposited on the surface of the alloy to form a dense corrosion product film. Therefore, increasing the Al content can increase the Al2O3 content in the surface film, thereby significantly improving the film layer density and achieving a significant improvement in corrosion resistance. In addition, the increase of solute Al atoms in the matrix will also lead to the precipitation of more CP phases during aging, thereby significantly improving the aging hardening response of the alloy.

[0015] 2. The existing semi-solid injection molding magnesium alloy is mainly Mg-Al-Zn-Mn alloy, and the magnesium alloy of the present application contains Al, Zn, Mn elements and a small amount of rare earth elements (RE). RE can combine with Al and Mn to form Al-RE or Al-Mn-RE phases, which can act as heterogeneous nucleation sites for eutectic Mg 17 Al 12 phase, increase the nucleation rate of eutectic phase, realize eutectic phase refinement, and significantly improve the mechanical properties of the alloy. In addition, the coarse lamellar discontinuous Mg 17 Al 12The phase (DP phase) is mainly precipitated from the grain boundary, and the Al-RE, Al-Mn-RE and the like are arranged at the defects such as the grain boundary, thereby inhibiting the precipitation of the coarse DP phase in the heat treatment process. In addition, the atomic radius of the rare earth element is greater than that of Mg and Al, so that after the rare earth element is added, the rare earth atoms dissolved in the matrix will hinder the diffusion of Mg and Al atoms, thereby slowing down the proliferation and coarsening of the DP phase in the aging process. Therefore, the strength of the magnesium alloy of the present application is obviously improved after aging, and the plasticity does not decrease significantly, while the existing commercial AZ91 semi-solid magnesium alloy forms and coarsens the DP phase rapidly after aging, thereby causing the strength to increase and the plasticity to decrease significantly. In addition, the addition of trace rare earth elements can also improve the compactness of the alloy corrosion product film and improve the corrosion resistance of the alloy.

[0016] 3, The magnesium alloy of the present application adds trace rare earth elements and trace Ca elements. The Ca element is enriched in the eutectic Mg 17 Al 12 The phase, reduces the potential difference between the phase and the magnesium matrix, thereby weakening the micro-electric couple corrosion and improving the corrosion resistance of the alloy. In addition, the Ca element is also enriched in the DP phase, improving the thermal stability of the DP phase and thereby inhibiting the coarsening of the DP phase. Therefore, the strength, plasticity and corrosion resistance of the magnesium alloy of the present application are all better than those of the existing commercial AZ91, AZ80 and the like semi-solid magnesium alloy.

[0017] 4, The existing technology improves the strength of the gravity casting AZ91 magnesium alloy through solid solution aging treatment. Since the eutectic Mg 17 Al 12Compared to the coarse eutectic phase, it generally requires higher solution temperature (usually above 415℃) and longer solution time (usually 5-24h) to dissolve the eutectic phase into the matrix. The semi-solid injection molding technology adopted in the present application has a much faster solidification rate than the conventional solidification, thus the eutectic phase is much finer. Meanwhile, the addition of trace RE elements in the present application can further refine the eutectic phase. Therefore, the eutectic phase in the present application can be fully dissolved into the matrix at a lower solution temperature (390-410℃) and shorter solution time (0.5-3h), which significantly shortens the heat treatment time and reduces the processing cost. In addition, the prior art usually ages the gravity cast commercial AZ91 magnesium alloy at 175-220℃ to improve its strength. However, compared to the conventionally solidified AZ91 magnesium alloy, the semi-solid AZ91 magnesium alloy has more Al solute atoms dissolved in the matrix. If the aging temperature is 175-220℃, the DP phase will rapidly proliferate and coarsen, thus significantly reducing the plasticity of the alloy. Therefore, the previous aging temperature is not suitable for the semi-solid injection molded magnesium alloy. The present application adopts an aging temperature of 150-170℃, at which the DP phase precipitates and coarsens slowly, which can improve the strength of the alloy without significantly reducing its plasticity.

[0018] 5. The prior art usually adopts single-stage aging to improve the strength of the gravity cast AZ91 magnesium alloy. However, due to the lower suitable aging temperature of the semi-solid magnesium alloy, if single-stage aging is adopted, not only is the peak aging time long, but the fine platelet-shaped continuous Mg 17 Al 12 The strengthening phase (CP phase) has a low number density, which leads to poor aging hardening effect of the alloy. The present application adopts a two-stage aging heat treatment system for the semi-solid injection molded magnesium alloy. After semi-solid injection molding and cooling, there are residual dislocations in the alloy, and dislocations are effective nucleation sites for CP phase. Therefore, the present application first ages at 120-130℃ for 5-15h, which is to promote the pre-nucleation of CP phase. At the same time, due to the low aging temperature, less DP phase precipitates, which does not lead to a decrease in the plasticity of the alloy. Then, the alloy is aged at 150-170℃ for 5-25h. Since a large number of nucleation sites for CP phase have been formed in the previous stage, the precipitation of CP phase in the subsequent aging stage is significantly promoted, which increases the number density of CP phase, shortens the time required to reach the peak hardness, and thus inhibits the precipitation and coarsening of DP phase at high temperature. For example, the magnesium alloy in the present application can reach the peak hardness after aging at 120℃ for 15h and then at 150℃ for 25h, while the semi-solid magnesium alloy without low-temperature aging needs to be aged at 150℃ for 35h to reach the peak hardness. Therefore, the two-stage aging heat treatment system adopted in the present application can increase the number density of CP phase while inhibiting the precipitation and coarsening of DP phase, which greatly improves the mechanical properties of the alloy after aging.

[0019] 6. The high-toughness and corrosion-resistant magnesium alloy provided by the application is suitable for semi-solid injection molding technology. After the semi-solid castings prepared by the high-toughness and corrosion-resistant magnesium alloy are subjected to solid solution and double-stage aging heat treatment, the yield strength is greater than or equal to 200 MPa, the tensile strength is greater than or equal to 320 MPa, the elongation is greater than or equal to 10%, and the average corrosion rate after immersion in a 3.5 wt.% NaCl solution for 14 days is less than or equal to 0.15 mm / y. The comprehensive performance of the high-toughness and corrosion-resistant magnesium alloy is significantly better than that of the existing commercial AZ91 and AZ80 semi-solid injection molded magnesium alloys. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 SEM image of the microstructure of the magnesium alloy prepared for Example 1.

[0021] Figure 2 SEM image of the microstructure of the magnesium alloy prepared for Example 2.

[0022] Figure 3 EDS image of the microstructure of the magnesium alloy prepared for Example 2. DETAILED DESCRIPTION

[0023] The application will be described in detail below in combination with the drawings and examples. Example 1

[0024] This example is the preparation of a high-toughness and corrosion-resistant semi-solid injection molded magnesium alloy. The chemical composition of the magnesium alloy is designed as follows (wt.%): Al: 9.6%, Zn: 0.67%, Mn: 0.13%, Ca: 0.12%, Nd: 0.3%, Gd: 0.4%, and the sum of unavoidable impurities is less than or equal to 0.05%, and the balance is magnesium. The preparation process of the magnesium alloy is as follows: (1) Under the protection of inert gas, pure magnesium, pure aluminum, pure zinc, and magnesium-manganese intermediate alloy are sequentially added according to the component ratio, and heated and melted at 710°C; then magnesium-calcium intermediate alloy, magnesium-neodymium intermediate alloy, and magnesium-gadolinium intermediate alloy are added, stirred uniformly at 700°C, and subjected to refining degassing and slag removal, to obtain a magnesium alloy melt, which is poured into a mold to form a magnesium alloy ingot; (2) The magnesium alloy ingot obtained in step (1) is cut into magnesium alloy semi-solid billet particles, which are rectangular columnar structures with a particle size of 1.2 mm in length, 1.2 mm in width, and 3 mm in height; (3) The semi-solid billet particles obtained in step (2) are fed into the feeding hopper of an injection molding machine, and then fed into a metal sleeve; under the combined action of screw shearing and sleeve external heater, the particles are melted to the semi-solid interval (solid phase rate is 20%); under the action of a high-speed injection system, the semi-solid slurry is injected into a preheated mold cavity at an injection temperature of 600°C, an injection speed of 2 m / s, and an injection pressure of 70 MPa, and the molded part is obtained after cooling and solidification and demolding; (4) the shaped piece obtained in step (3) is subjected to solid solution heat treatment under argon protection at a temperature of 395 ℃ for 3 h, followed by water quenching to obtain a solid solution semi-solid shaped piece; (5) the solid solution semi-solid shaped piece obtained in step (4) is subjected to two-stage aging heat treatment, i.e., aging at 120 ℃ for 15 h and aging at 155 ℃ for 23 h, to obtain the high-strength and high-toughness corrosion-resistant Mg-9.6Al-0.67Zn-0.13Mn-0.12Ca-0.3Nd-0.4Gd semi-solid injection molded magnesium alloy.

[0025] The microstructure SEM image of the magnesium alloy prepared in the example is shown in FIG. 1. Figure 1 As can be seen from the image, the magnesium alloy has a large number of fine platelet-shaped continuous Mg 17 Al 12 strengthening phases (CP phases).

[0026] The magnesium alloy obtained in step (5) of the example has significantly improved corrosion resistance, and the average corrosion rate of the alloy after immersion in a 3.5wt.% NaCl solution for 14 days is about 0.13 mm / y. Meanwhile, the magnesium alloy also has high strength and high toughness, with a yield strength of 205 MPa, a tensile strength of 320 MPa, and an elongation of 11.2%.

[0027] Comparative Example 1: The corrosion rate of a commercial AZ91 semi-solid magnesium alloy with the same shape and size as in Example 1 is 3 mm / y, the yield strength is 170 MPa, the tensile strength is 300 MPa, and the elongation is 8%. Example 2:

[0028] The example is the preparation of a high-strength and high-toughness corrosion-resistant semi-solid injection molded magnesium alloy. The chemical composition of the magnesium alloy is (wt.%): Al: 10.0%, Zn: 0.78%, Mn: 0.23%, Ca: 0.15%, Ce: 0.25%, Sm: 0.4%, and unavoidable impurities totaling ≤0.05%, with the balance being magnesium. The preparation process of the magnesium alloy is as follows: (1) under inert gas protection, pure magnesium, pure aluminum, pure zinc, and magnesium-manganese intermediate alloy are sequentially added and heated to melt at 720 ℃; then magnesium-calcium intermediate alloy, magnesium-cerium intermediate alloy, and magnesium-samarium intermediate alloy are added and stirred uniformly at 710 ℃, and after refining, degassing, and slag removal, a magnesium alloy melt is obtained, which is poured into a mold to form a magnesium alloy ingot; (2) the magnesium alloy ingot obtained in step (1) is cut into magnesium alloy semi-solid billet particles, which have a rectangular columnar structure and a particle size of 1.2 mm in length, 1.2 mm in width, and 3 mm in height; (3) The semi-solid billet particles obtained in step (2) are fed into the hopper of an injection molding machine, and then into a metal sleeve; under the combined action of the screw shearing and the sleeve outer heater, the particles are melted to the semi-solid interval (solid phase rate is 45%); under the action of the high-speed injection system, the semi-solid slurry is injected into the preheated mold cavity at an injection temperature of 580℃, an injection speed of 4.5 m / s and an injection pressure of 95 MPa, and after cooling and solidification, the molded part is obtained; (4) The molded part obtained in step (3) is subjected to solid solution heat treatment under argon protection, the temperature is 410℃, the time is 1.5h, and then water quenching is carried out, and a solid solution semi-solid molded part is obtained; (5) The solid solution semi-solid molded part obtained in step (4) is subjected to two-stage aging heat treatment, first aging at 130℃ for 5h, and then aging at 160℃ for 15h, and finally a high-strength and high-toughness corrosion-resistant Mg-10Al-0.78Zn-0.23Mn-0.15Ca-0.25Ce-0.4Sm semi-solid injection molded magnesium alloy is obtained.

[0029] The magnesium alloy prepared in this example has a large number of fine platelet-shaped continuous Mg 17 Al 12 The number density of the strengthening phase (CP phase) is high.

[0030] The SEM microstructure of the magnesium alloy prepared in this example is shown in Figure 2 It can be seen that the bright phase is a rare earth phase Al8Mn4(Ce,Sm).

[0031] In the magnesium alloy prepared in this example, Ca is enriched in the Mg 17 Al 12 phase, as shown in Figure 3 .

[0032] The average corrosion rate of the magnesium alloy obtained in step (5) of this example after immersion in 3.5wt.% NaCl solution for 14 days is 0.09mm / y, the yield strength is 211MPa, the tensile strength is 328MPa, and the elongation is 10.8%.

[0033] Comparative Example 2: The difference between this example and Example 2 is that the magnesium alloy is subjected to single-stage aging heat treatment, and the peak hardness is reached after aging at 160℃ for 25h, and after aging, the yield strength is 185MPa, the tensile strength is 305MPa, and the elongation is 8.7%. Example 3:

[0034] The embodiment is preparation of high-toughness corrosion-resistant semi-solid injection molded magnesium alloy. The chemical composition of the magnesium alloy is designed as follows (wt.%): Al: 10.4%, Zn: 0.75%, Mn: 0.24%, Ca: 0.18%, Ce: 0.4%, Nd: 0.4%, unavoidable impurities: ≤0.05%, and the balance is magnesium. The preparation process of the magnesium alloy is as follows: (1) Under the protection of inert gas, pure magnesium, pure aluminum, pure zinc and magnesium-manganese intermediate alloy are sequentially added, and heated and melted at 720°C; then magnesium-calcium intermediate alloy, magnesium-cerium intermediate alloy and magnesium-neodymium intermediate alloy are added, stirred uniformly at 710°C, and after refining, degassing and slag removal, a magnesium alloy melt is obtained, which is poured into a mold to form a magnesium alloy ingot; (2) The magnesium alloy ingot obtained in step (1) is cut into magnesium alloy semi-solid billet particles, which are rectangular columnar structures, and the particle size is 1.2 mm in length, 1.2 mm in width and 3 mm in height; (3) The semi-solid billet particles obtained in step (2) are fed into the feeding hopper of an injection molding machine, and then into a metal sleeve; under the combined action of screw shearing and sleeve external heater, the particles are melted to the semi-solid interval (solid phase rate is 55%); under the action of high-speed injection system, the semi-solid slurry is injected into the preheated mold cavity at an injection temperature of 570°C, an injection speed of 5 m / s and an injection pressure of 100 MPa, and after cooling and solidification, the molded part is obtained; (4) The molded part obtained in step (3) is subjected to solid solution heat treatment under argon protection at a temperature of 410°C for 2h, and then water quenching is performed to obtain a solid solution semi-solid molded part; (5) The solid solution semi-solid molded part obtained in step (4) is subjected to two-stage aging heat treatment, specifically: first aging treatment at 125°C for 10h, and then aging treatment at 165°C for 10h, to finally obtain high-toughness corrosion-resistant Mg-10.4Al-0.75Zn-0.24Mn-0.18Ca-0.4Ce-0.4Nd semi-solid injection molded magnesium alloy.

[0035] The average corrosion rate of the magnesium alloy obtained in step (5) of the embodiment after immersion in 3.5wt.% NaCl solution for 14 days is 0.07 mm / y, the yield strength is 215 MPa, the tensile strength is 335 MPa, and the elongation is 10.3%.

[0036] Comparative Example 3: The corrosion rate of the commercial AZ80 semi-solid magnesium alloy with the same shape and size as in Example 3 is 3.5 mm / y, the yield strength is 165 MPa, the tensile strength is 296 MPa, and the elongation is 8.2%. Example 4:

[0037] The embodiment is preparation of high-toughness corrosion-resistant semi-solid injection molded magnesium alloy. The chemical composition of the magnesium alloy is designed as follows (wt.%): Al: 9.7%, Zn: 0.7%, Mn: 0.15%, Ca: 0.18%, Nd: 0.75%, unavoidable impurities: ≤0.05%, and the balance is magnesium. The preparation process of the magnesium alloy is as follows: (1) Under the protection of inert gas, pure magnesium, pure aluminum, pure zinc and magnesium-manganese intermediate alloy are sequentially added and heated and melted at 705 ℃; then magnesium-calcium intermediate alloy and magnesium-neodymium intermediate alloy are sequentially added and stirred uniformly at 695 ℃, and after refining, degassing and slag removal, a magnesium alloy melt is obtained, which is poured into a mold to form a magnesium alloy ingot; (2) The magnesium alloy ingot obtained in step (1) is cut into magnesium alloy semi-solid billet particles, which are rectangular columnar structures, and the particles are 1.2 mm long, 1.2 mm wide and 3 mm high; (3) The semi-solid billet particles obtained in step (2) are fed into the feeding hopper of an injection molding machine, and then fed into a metal sleeve; under the joint action of screw shearing and sleeve external heater, the particles are melted to the semi-solid interval (solid phase rate is 25%); under the action of a high-speed injection system, the semi-solid slurry is injected into a preheated mold cavity at an injection temperature of 595 ℃, an injection speed of 3 m / s and an injection pressure of 80 MPa, and after cooling and solidification, the molded part is obtained; (4) The molded part obtained in step (3) is subjected to solid solution heat treatment under the protection of argon, at a temperature of 400 ℃ for 3 h, and then subjected to water quenching to obtain a solid solution semi-solid molded part; (5) The solid solution semi-solid molded part obtained in step (4) is subjected to two-stage aging heat treatment, i.e., aging at 120 ℃ for 10 h and aging at 170 ℃ for 5 h, to obtain high-toughness corrosion-resistant Mg-9.7Al-0.7Zn-0.15Mn-0.18Ca-0.75Nd semi-solid injection molded magnesium alloy.

[0038] The average corrosion rate of the magnesium alloy obtained in step (5) of the embodiment after immersion in 3.5wt.% NaCl solution for 14 days is 0.1 mm / y, the yield strength is 208 MPa, the tensile strength is 330 MPa, and the elongation is 11.0%.

[0039] Comparative Example 4 The difference between the embodiment 4 and the comparative example 4 is that the magnesium alloy in the example is subjected to single-stage aging heat treatment, and the peak hardness is reached after aging at 170 ℃ for 10 h. After aging, the yield strength is 191 MPa, the tensile strength is 314 MPa, and the elongation is 8.0%.

[0040] In summary, in the magnesium alloy of the present application, the added Ca element can be enriched in the eutectic Mg 17 Al 12In the phase, the potential difference between the phase and the matrix is reduced, the micro-electric couple corrosion is weakened, and the corrosion resistance is improved. The added rare earth elements can refine the eutectic phase and inhibit the coarse lamellar discontinuous Mg 17 Al 12 The precipitation of the phase (DP phase) significantly improves the strength and toughness of the alloy. The two-stage aging (low temperature + high temperature) can increase the number density of the strengthening phase (CP phase) on the one hand, and can inhibit the precipitation of the DP phase in the high-temperature aging process, so that the strength of the alloy after aging is greatly improved. The magnesium alloy of the application has high strength and toughness and corrosion resistance, and is suitable for semi-solid injection molding. The molding process can realize near-net molding of complex components, and the casting has few defects and dense structure, and has wide application prospect. 17 Al 12 The number density of the strengthening phase (CP phase), on the other hand, can inhibit the precipitation of the DP phase in the high-temperature aging process, so that the strength of the alloy after aging is greatly improved. The magnesium alloy of the application has high strength and toughness and corrosion resistance, and is suitable for semi-solid injection molding. The molding process can realize near-net molding of complex components, and the casting has few defects and dense structure, and has wide application prospect.

[0041] It should be particularly noted that the present application can have other various embodiments, and all similar substitutions and changes that do not deviate from the spirit and essence of the present application are considered to be included in the present application.

Claims

1. A high-toughness corrosion-resistant semi-solid injection molded magnesium alloy, characterized by: The magnesium alloy has the following chemical composition in percentage by weight: Aluminum: 8.6-11%, zinc: 0.5-1%, manganese: 0.05-0.4%, calcium: 0.05-0.2%, rare earth element RE: 0.6-2%, and the balance of magnesium and inevitable impurities.

2. The high tough corrosion resistant semi-solid injection molded magnesium alloy of claim 1, wherein: In the chemical composition of the magnesium alloy, aluminum is 9.5-10.5wt.%, zinc is 0.65-0.8wt.%, manganese is 0.1-0.25wt.%, calcium is 0.1-0.2wt.%, and rare earth element RE is 0.6-0.9%.

3. The high tough and corrosion resistant semi-solid injection molded magnesium alloy according to claim 1 or 2, characterized in that: The rare earth element RE is one or more of cerium, neodymium, samarium, and gadolinium.

4. The high tough and corrosion resistant semi-solid injection molded magnesium alloy of claim 3, wherein: The magnesium alloy has a yield strength of ≥200MPa, a tensile strength of ≥320MPa, an elongation of ≥10%, and an average corrosion rate of ≤0.15mm / y after immersion in a 3.5wt.% NaCl solution for 14 days.

5. The method for preparing high-strength, tough, and corrosion-resistant semi-solid injection-molded magnesium alloy according to claim 1, characterized in that: The preparation method comprises the following steps: (1) Under the protection of inert gas, pure magnesium, pure aluminum, pure zinc, and magnesium-manganese intermediate alloy are sequentially added according to the component ratio, and heated and melted at 670-750℃; then magnesium-calcium intermediate alloy and magnesium-RE intermediate alloy are sequentially added; after uniform stirring at 670-720℃, refining, degassing, and slag removal are performed to obtain a magnesium alloy melt, which is poured into a mold to form a magnesium alloy ingot; (2) The magnesium alloy ingot obtained in step (1) is cut into magnesium alloy semi-solid billet particles, which have a rectangular columnar structure and a particle size of 1-1.5mm in length, 1-1.5mm in width, and 2-4mm in height; (3) The semi-solid billet particles obtained in step (2) are fed into an injection molding machine for injection molding to obtain a molded part; (4) The molded part obtained in step (3) is subjected to solid solution heat treatment under the protection of argon, and then water quenching is performed to obtain a solid solution semi-solid molded part; (5) The solid solution semi-solid molded part obtained in step (4) is subjected to double-stage aging heat treatment to obtain the high-strength and high-toughness corrosion-resistant semi-solid injection molded magnesium alloy.

6. The method for preparing high-strength, tough, and corrosion-resistant semi-solid injection-molded magnesium alloy according to claim 5, characterized in that: In step (3), the injection molding process is as follows: the semi-solid billet particles are fed into the feeding hopper of the injection molding machine, and then into the metal sleeve; under the combined action of screw shearing and sleeve external heater, the particles are melted to the semi-solid interval; under the action of the high-speed injection system, the semi-solid slurry is injected into the preheated mold cavity, and the molded part is obtained after cooling and solidification.

7. The method for preparing high-strength, tough, and corrosion-resistant semi-solid injection-molded magnesium alloy according to claim 5, characterized in that: In step (3), the solid phase rate of the semi-solid interval is 20-55%; during the injection molding process, the injection temperature is 570-600℃, the injection speed is 2-5m / s, and the injection pressure is 70-100MPa.

8. The method for preparing high-strength, tough, and corrosion-resistant semi-solid injection-molded magnesium alloy according to claim 5, characterized in that: In step (4), the solid solution heat treatment temperature is 390-410℃, and the time is 0.5-3h.

9. The method for preparing high-strength, tough, and corrosion-resistant semi-solid injection-molded magnesium alloy according to claim 5, characterized in that: In step (5), the double-stage aging heat treatment is as follows: first aging at 120-130℃ for 5-15h, and then aging at 150-170℃ for 5-25h.

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