High-strength high-pressure die-casting magnesium alloy and preparation method thereof

Abstract

The invention discloses a high-strength high-pressure die-casting magnesium alloy and a preparation method thereof, and belongs to the technical field of non-ferrous metal materials. The high-strength and high-pressure die-casting magnesium alloy provided by the invention is prepared from the following components in percentage by weight: 6 to 10 percent of Zn, 6 to 10 percent of Al, 0.1 to 1 percent of La, 0.1 to 2 percent of Ce, 0.001 to 0.1 percent of Sm, 0.001 to 0.1 percent of Y, 0.001 to 0.1 percent of Nd, 0.01 to 0.5 percent of Bi, 0.001 to 0.3 percent of Sr, 0.001 to 0.2 percent of Ca, 0 to 0.1 percent of Zr and the balance of Mg and inevitable impurity elements. The high-strength high-pressure die-casting magnesium alloy with high strength and excellent forming performance is obtained by optimizing alloy components, increasing the content of Al and Zn alloy elements, adding rare earth mixed elements and adding Ca, Bi, Sr and other alloy elements to refine grains.

Description

Technical Field

[0001] The present invention belongs to the technical field of nonferrous metal materials, and in particular relates to a high-strength and high-pressure die-cast magnesium alloy and a preparation method thereof. Background Art

[0002] Magnesium alloys are widely used in the automotive, aerospace, and electronic equipment industries due to their low density, high specific strength, good shock absorption properties, and excellent casting properties. Die-casting is one of the important methods for forming magnesium alloys, capable of achieving near-net-shape shapes of complex parts. However, the low strength of traditional die-cast magnesium alloys (such as AZ91D and AM60B) makes them difficult to use in load-bearing structures, limiting their wider application. Therefore, the development of high-strength die-cast magnesium alloys has important industrial and social value for expanding the application of magnesium alloys.

[0003] Although the existing technology can improve the performance of magnesium alloys to a certain extent by adding rare earth elements, optimizing alloy composition and improving die-casting process, it still has problems such as high cost, complex process, poor mechanical properties and die-casting performance. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a high-strength, high-pressure die-cast magnesium alloy and its preparation method. The magnesium alloy provided by the present invention has excellent mechanical properties and die-casting properties, broadening the application of magnesium alloys in high-strength applications.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] The present invention provides a high-strength and high-pressure die-cast magnesium alloy, which is composed of the following components in weight percentage: Zn 6-10%, Al 6-10%, La 0.1-1%, Ce 0.1-2%, Sm 0.001-0.1%, Y 0.001-0.1%, Nd 0.001-0.1%, Bi 0.01-0.5%, Sr 0.001-0.3%, Ca 0.001-0.2%, Zr 0-0.1%, and the balance being Mg and unavoidable impurity elements.

[0008] Furthermore, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 6-8%, Al 6-8%, La 0.5-1%, Ce 1-2%, Sm 0.01-0.02%, Y 0.01-0.03%, Nd 0.005-0.01%, Bi 0.3-0.4%, Sr 0.2-0.3%, Ca 0.08-0.1%, Zr 0-0.08%, and the balance is Mg and unavoidable impurity elements, wherein the total weight of the impurity elements is ≤0.1%.

[0009] Furthermore, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 8-10%, Al 6-8%, La 0.5-1%, Ce 1-2%, Sm 0.02-0.3%, Y 0.02-0.03%, Nd 0.01-0.02%, Bi 0.2-0.4%, Sr 0.1-0.3%, Ca 0.09-0.1%, Zr 0.07-0.09%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%.

[0010] Furthermore, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 8-10%, Al 8-10%, La 0.5-0.7%, Ce 1.2-1.5%, Sm 0.03-0.04%, Y 0.01-0.02%, Nd 0.01-0.02%, Bi 0.1-0.4%, Sr 0.1-0.2%, Ca 0.08-0.1%, Zr 0.06-0.08%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%.

[0011] Furthermore, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 8-9%, Al 8-9%, La 0.1-0.3%, Ce 0.1-0.8%, Sm 0.02-0.03%, Y 0.03-0.04%, Nd 0.01-0.02%, Bi 0.2-0.3%, Sr 0.1-0.2%, Ca 0.1-0.15%, Zr 0.06-0.07%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%.

[0012] Furthermore, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 7-9%, Al 8-9%, La 0.5-0.8%, Ce 1.3-1.6%, Sm 0.02-0.04%, Y 0.01-0.02%, Nd 0.02-0.03%, Bi 0.03-0.5%, Sr 0.02-0.3%, Ca 0.01-0.2%, Zr 0.05-0.06%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%.

[0013] Furthermore, the high-strength and high-pressure die-cast magnesium alloy has a tensile strength of 281-308 MPa, a yield strength of 181-228 MPa, an elongation of 4.1-5.6%, an alloy solidification range of 236.67-258.35° C., and a thermal cracking coefficient of 4-12.

[0014] Technical principle: The present invention optimizes the alloy composition, increases the content of Al and Zn alloying elements, adds rare earth mixed elements (including one or more of La, Ce, Sm, Nd, and Y), and adds alloying elements such as Ca, Bi, and Sr to refine the grains, thereby obtaining a high-strength, high-pressure die-cast magnesium alloy with high strength and excellent forming properties.

[0015] The second technical solution of the present invention:

[0016] The present invention also provides a method for preparing the high-strength and high-pressure die-cast magnesium alloy described in the above technical solution, comprising the following steps: weighing raw materials according to the alloy component ratio, and sequentially smelting, refining, deslagging and casting to obtain a magnesium alloy ingot; die-casting the magnesium alloy ingot to obtain the high-strength and high-pressure die-cast magnesium alloy.

[0017] Furthermore, the raw materials include Mg ingots, Zn ingots, Al ingots, mixed rare earth, Mg-Ca master alloy, Al-Sr master alloy, Mg-Bi master alloy and Mg-Zr master alloy; and / or,

[0018] The temperature of the refining and deslagging is 730-760° C., the time is 20-30 minutes, and the amount of the refining agent used is 1-2% of the total mass of the raw materials.

[0019] Furthermore, the die-casting process parameters include: injection pressure of 40±5MPa, injection speed of 5±0.5m / s, magnesium alloy melt temperature of 690±10℃, mold temperature of 200±10℃, mass ratio of release agent and water of 1:80, and atmosphere of a mixed atmosphere of SF6 and N2.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] The present invention improves the strength of the alloy while ensuring the fluidity and forming performance of the alloy by adding elements such as Zn, Al, RE (including La, Ce, Sm, Nd and Y), Ca, Sr, Bi, and controlling the content of each alloy element. Among them, Al and Zn can significantly improve the comprehensive performance of the magnesium alloy through solid solution strengthening, precipitation phase formation and process performance optimization. Al provides solid solution strengthening and β phase precipitation strengthening, and Zn supplements aging strengthening to form a multi-scale strengthening mechanism. The addition of Al can reduce the melting point of the magnesium alloy, improve the melt fluidity, and reduce casting defects (such as shrinkage cavities); the addition of rare earth elements such as La, Ce, Sm, Nd, and Y can effectively refine the grains and optimize the comprehensive mechanical properties of the alloy. Rare earth elements can also reduce the solidification range of the magnesium alloy and reduce the generation of thermal cracks during the casting process. The three elements of Ca, Sr, and Bi play a synergistic role in further refining the grains, and the Bi element can also inhibit the growth of Mg in aluminum-containing magnesium alloys. 17 Al 12 Phase coarsening, optimizing comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0023] Figure 1 Schematic diagram of the influencing factors of hot cracking rods;

[0024] Figure 2 Graphs showing the influencing factors of hot cracking rods of magnesium alloys in Example 7 and Comparative Example 1, where (a) and (b) are from Example 7, and (c) and (d) are from Comparative Example 1. (a) and (c) are graphs showing individual hot cracking rods, while (b) and (d) are graphs showing the hot cracking rods placed in a mold.

[0025] Figure 3 2 are stress-strain curves of the magnesium alloys in Example 7 and Comparative Example 1. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] An embodiment of the present invention provides a high-strength, high-pressure die-cast magnesium alloy, comprising, by weight percentage, 6-10% Zn, 6-10% Al, 0.1-1% La, 0.1-2% Ce, 0.001-0.1% Sm, 0.001-0.1% Y, 0.001-0.1% Nd, 0.001-0.1% Bi, 0.01-0.5% Sr, 0.001-0.3% Ca, 0.001-0.2% Zr, and the balance being Mg and unavoidable impurity elements. The present invention optimizes the alloy composition, increases the content of Al and Zn alloying elements, simultaneously adds rare earth mixed elements (including La, Ce, Sm, Nd, and Y), and adds alloying elements such as Ca, Bi, and Sr to refine the grains, thereby obtaining a high-strength, high-pressure die-cast magnesium alloy with high strength and excellent formability.

[0029] In a preferred embodiment, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 6-8%, Al 6-8%, La 0.5-1%, Ce 1-2%, Sm 0.01-0.02%, Y0.01-0.03%, Nd0.005-0.01%, Bi 0.3-0.4%, Sr 0.2-0.3%, Ca 0.08-0.1%, Zr 0-0.08%, and the balance is Mg and unavoidable impurity elements, wherein the total weight of the impurity elements is ≤0.1%. For example, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components, calculated by weight percentage: Zn 6.32%, Al 6.03%, La 0.56%, Ce 1.28%, Sm 0.02%, Y 0.03%, Nd 0.01%, Bi 0.32%, Sr 0.21%, Ca 0.09%, Zr 0.08%, and the remainder is Mg and unavoidable impurity elements, wherein the total weight of the impurity elements is ≤0.1%.

[0030] In a preferred embodiment, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 8-10%, Al 6-8%, La 0.5-1%, Ce 1-2%, Sm 0.02-0.3%, Y0.02-0.03%, Nd0.01-0.02%, Bi 0.2-0.4%, Sr 0.1-0.3%, Ca 0.09-0.1%, Zr 0.07-0.09%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%. For example, a high-strength and high-pressure die-cast magnesium alloy is composed of the following components by weight: Zn 8.02%, Al 6.48%, La 0.62%, Ce 1.38%, Sm 0.03%, Y 0.03%, Nd 0.02%, Bi 0.29%, Sr 0.19%, Ca 0.1%, Zr 0.07%, with the remainder being Mg and unavoidable impurity elements, and the total content of impurity elements being ≤0.1%; another example is a high-strength and high-pressure die-cast magnesium alloy is composed of the following components by weight: Zn 9.56%, Al 6.37%, La 0.61%, Ce 1.34%, Sm 0.02%, Y 0.02%, Nd 0.01%, Bi 0.37%, Sr 0.22%, Ca 0.09%, Zr 0.09%, the balance is Mg and unavoidable impurity elements, the total content of impurity elements ≤ 0.1%.

[0031] In a preferred embodiment, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 8-10%, Al 8-10%, La 0.5-0.7%, Ce 1.2-1.5%, Sm 0.03-0.04%, Y 0.01-0.02%, Nd 0.01-0.02%, Bi 0.1-0.4%, Sr 0.1-0.2%, Ca 0.08-0.1%, Zr0.06-0.08%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%. For example, a high-strength and high-pressure die-cast magnesium alloy is composed of the following components by weight: Zn 8.11%, Al 8.01%, La 0.64%, Ce 1.42%, Sm 0.03%, Y 0.02%, Nd 0.02%, Bi 0.33%, Sr 0.18%, Ca 0.08%, and Zr 0.08%, with the remainder being Mg and unavoidable impurity elements, and the total content of impurity elements being ≤0.1%; for another example, a high-strength and high-pressure die-cast magnesium alloy is composed of the following components by weight: Zn 8.09%, Al 9.76%, La 0.58%, Ce 1.29%, Sm 0.04%, Y 0.02%, Nd 0.01%, Bi 0.31%, Sr 0.15%, Ca 0.1%, and Zr. 0.06%, the balance is Mg and unavoidable impurity elements, the total content of impurity elements ≤ 0.1%.

[0032] In a preferred embodiment, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 8-9%, Al 8-9%, La 0.1-0.3%, Ce 0.1-0.8%, Sm 0.02-0.03%, Y 0.03-0.04%, Nd 0.01-0.02%, Bi 0.2-0.3%, Sr 0.1-0.2%, Ca 0.1-0.15%, Zr0.06-0.07%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%. For example, a high-strength and high-pressure die-cast magnesium alloy is composed of the following components, calculated by weight: Zn 8.09%, Al 8.04%, La 0.24%, Ce 0.6%, Sm 0.03%, Y 0.04%, Nd 0.02%, Bi 0.28%, Sr 0.16%, Ca 0.14%, and Zr 0.07%, with the remainder being Mg and unavoidable impurity elements, and the total content of impurity elements being ≤0.1%.

[0033] In a preferred embodiment, the high-strength and high-pressure die-cast magnesium alloy is composed of the following components in weight percentage: Zn 7-9%, Al 8-9%, La 0.5-0.8%, Ce 1.3-1.6%, Sm 0.02-0.04%, Y 0.01-0.02%, Nd 0.02-0.03%, Bi 0.03-0.5%, Sr 0.02-0.3%, Ca 0.01-0.2%, Zr0.05-0.06%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%. For example, a high-strength and high-pressure die-cast magnesium alloy is composed of the following components, calculated by weight percentage: Zn 8.13%, Al 8.02%, La 0.65%, Ce 1.46%, Sm 0.02%, Y 0.02%, Nd 0.02%, Bi 0.48%, Sr 0.29%, Ca 0.18%, and Zr 0.06%, with the remainder being Mg and unavoidable impurity elements, and the total content of impurity elements being ≤0.1%; for another example, a high-strength and high-pressure die-cast magnesium alloy is composed of the following components, calculated by weight percentage: Zn 7.99%, Al 8.12%, La 0.72%, Ce 1.52%, Sm 0.04%, Y 0.01%, Nd 0.03%, Bi 0.03%, Sr 0.02%, Ca 0.01%, and Zr. 0.05%, the balance is Mg and unavoidable impurity elements, the total content of impurity elements ≤ 0.1%.

[0034] In a preferred embodiment, the high-strength and high-pressure die-cast magnesium alloy has a tensile strength of 281-308 MPa, a yield strength of 181-228 MPa, an elongation of 4.1-5.6%, an alloy solidification range of 236.67-258.35° C., and a thermal cracking coefficient of 4-12.

[0035] The present invention also provides a method for preparing the high-strength and high-pressure die-cast magnesium alloy described in the above technical solution, comprising the following steps: weighing raw materials according to the alloy component ratio, and sequentially smelting, refining, deslagging and casting to obtain a magnesium alloy ingot; die-casting the magnesium alloy ingot to obtain the high-strength and high-pressure die-cast magnesium alloy.

[0036] In a preferred embodiment, the raw materials include Mg ingots, Zn ingots, Al ingots, mixed rare earth, Mg-Ca master alloy, Al-Sr master alloy, Mg-Bi master alloy and Mg-Zr master alloy.

[0037] In a preferred embodiment, the melting temperature of the Mg ingot is 680-700°C; the melting temperature of the Al ingot and the Zn ingot is 710-720°C; the melting temperature of the mixed rare earth, Mg-Ca master alloy, Al-Sr master alloy, Mg-Bi master alloy and Mg-Zr master alloy is 730-750°C.

[0038] In a preferred embodiment, a mixed gas of SF6 and CO2 is introduced during the smelting process; the volume concentration of SF6 in the mixed gas is 0.1-1.0%, and the remainder is N2; before smelting the Mg ingot, a refining agent is also added to the bottom of the furnace to prevent the magnesium alloy from burning during the melting process; the refining agent is selected from RJ-2 flux.

[0039] In a preferred embodiment, the refining and slagging temperature is 730-760° C., the time is 20-30 min, and the amount of refining agent used is 1-2% of the total mass of the raw materials; the refining agent is selected from RJ-5 flux.

[0040] In a preferred embodiment, the die-casting process parameters include: injection pressure of 40±5MPa, injection speed of 5±0.5m / s, magnesium alloy melt temperature of 690±10℃, mold temperature of 200±10℃, mass ratio of release agent to water of 1:80, and atmosphere of a mixed atmosphere of SF6 and N2. The volume concentration of SF6 in the mixed atmosphere is extremely low (0.1-1.0%), and the rest is N2. The minimum amount of SF6 is used as much as possible to achieve the protective effect. The die-casting process parameters in the present invention are formulated based on a comprehensive consideration of the alloy's forming properties and its solidus-liquidus temperature. During the die-casting process, the fluidity of different magnesium alloys varies, and the die-casting process parameters have a significant impact on the forming effect of alloys with different fluidities. High-pressure, high-speed, and high-temperature die-casting will improve the flow formability of the alloy, but excessively high die-casting speed and pressure will cause the alloy to "leak" during the die-casting process. The selection of the die-casting temperature also needs to consider whether the solidus-liquidus temperature of the alloy is appropriate. The inventors determined the die-casting process parameters based on the differences in fluidity and die-casting temperature between the most commonly used magnesium alloys (such as AZ91D) and the alloy of the present invention.

[0041] In the present invention, the alloying efficiency of the Al ingot used is 100%, the alloying efficiency of the Zn ingot is 100%, and the alloying efficiency of the mixed rare earth is 80%.

[0042] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0043] Example 1

[0044] A high-strength, high-pressure die-cast magnesium alloy comprises the following components, measured by weight: 6.32% Zn, 6.03% Al, 0.56% La, 1.28% Ce, 0.02% Sm, 0.03% Y, 0.01% Nd, 0.32% Bi, 0.21% Sr, 0.09% Ca, and 0.08% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0045] A method for preparing a high-strength and high-pressure die-cast magnesium alloy, comprising the following steps:

[0046] S1. Weigh Mg ingots, Zn ingots, Al ingots, mixed rare earth, Mg-Ca master alloy, Al-Sr master alloy, Mg-Bi master alloy and Mg-Zr master alloy according to the alloy component ratio.

[0047] S2. Dry the above raw materials at 120±5°C for 3h.

[0048] S3. A mixed gas of SF6 and CO2 (the volume concentration of the mixed gas is 0.1% SF6, and the rest is N2) is introduced into the melting furnace for protection. At the same time, a layer of RJ-2 flux is laid on the bottom of the melting furnace to prevent oxidation and combustion of the subsequent magnesium ingot during melting. Then, the Mg ingot is placed in the melting furnace, and the temperature is raised to 687° C. to melt the Mg ingot. Subsequently, the temperature is adjusted to 718° C., and Al ingots and Zn ingots are added. After melting, the temperature is adjusted to 732° C., and mixed rare earth, Mg-Ca master alloy, Al-Sr master alloy, Mg-Bi master alloy, and Mg-Zr master alloy are added. After sufficient melting, an alloy liquid is obtained.

[0049] S4. Adjust the temperature of the alloy liquid to 738° C., add 2% RJ-5 flux by weight of the total raw materials, stir with argon, stir for 10 minutes, and then let it stand for 20 minutes to obtain a refined alloy liquid.

[0050] S5. Casting the refined alloy liquid to obtain a magnesium alloy ingot.

[0051] S6. The above-mentioned magnesium alloy ingot is put into the machine-side furnace for remelting, and then die-casting is carried out. The process parameters of die-casting are: injection pressure of 40±5MPa, injection speed of 5±0.5m / s, magnesium alloy melt temperature of 690±10℃, mold temperature of 200±10℃, mass ratio of release agent and water of 1:80, atmosphere of mixed gas atmosphere of SF6 and CO2 (the volume concentration of SF6 in the mixed atmosphere is 0.1%, and the rest is N2), to obtain high-strength and high-pressure die-cast magnesium alloy.

[0052] Example 2

[0053] A high-strength, high-pressure die-cast magnesium alloy comprises the following components, measured by weight: 8.02% Zn, 6.48% Al, 0.62% La, 1.38% Ce, 0.03% Sm, 0.03% Y, 0.02% Nd, 0.29% Bi, 0.19% Sr, 0.1% Ca, and 0.07% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0054] The preparation method of the high-strength and high-pressure die-cast magnesium alloy is the same as that in Example 1.

[0055] Example 3

[0056] A high-strength, high-pressure die-cast magnesium alloy comprises the following components, measured by weight: 9.56% Zn, 6.37% Al, 0.61% La, 1.34% Ce, 0.02% Sm, 0.02% Y, 0.01% Nd, 0.37% Bi, 0.22% Sr, 0.09% Ca, and 0.09% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0057] The preparation method of the high-strength and high-pressure die-cast magnesium alloy is the same as that in Example 1.

[0058] Example 4

[0059] A high-strength, high-pressure die-cast magnesium alloy comprises the following components, measured by weight: 8.11% Zn, 8.01% Al, 0.64% La, 1.42% Ce, 0.03% Sm, 0.02% Y, 0.02% Nd, 0.33% Bi, 0.18% Sr, 0.08% Ca, and 0.08% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0060] The preparation method of the high-strength and high-pressure die-cast magnesium alloy is the same as that in Example 1.

[0061] Example 5

[0062] A high-strength, high-pressure die-cast magnesium alloy comprises the following components, measured by weight: 8.09% Zn, 9.76% Al, 0.58% La, 1.29% Ce, 0.04% Sm, 0.02% Y, 0.01% Nd, 0.31% Bi, 0.15% Sr, 0.1% Ca, and 0.06% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0063] The preparation method of the high-strength and high-pressure die-cast magnesium alloy is the same as that in Example 1.

[0064] Example 6

[0065] A high-strength, high-pressure die-cast magnesium alloy comprises the following components, measured by weight: 8.09% Zn, 8.04% Al, 0.24% La, 0.6% Ce, 0.03% Sm, 0.04% Y, 0.02% Nd, 0.28% Bi, 0.16% Sr, 0.14% Ca, and 0.07% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0066] The preparation method of the high-strength and high-pressure die-cast magnesium alloy is the same as that in Example 1.

[0067] Example 7

[0068] A high-strength, high-pressure die-cast magnesium alloy comprises the following components, measured by weight: 8.13% Zn, 8.02% Al, 0.65% La, 1.46% Ce, 0.02% Sm, 0.02% Y, 0.02% Nd, 0.48% Bi, 0.29% Sr, 0.18% Ca, and 0.06% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0069] The preparation method of the high-strength and high-pressure die-cast magnesium alloy is the same as that in Example 1.

[0070] Example 8

[0071] A high-strength, high-pressure die-cast magnesium alloy comprises the following components, measured by weight: 7.99% Zn, 8.12% Al, 0.72% La, 1.52% Ce, 0.04% Sm, 0.01% Y, 0.03% Nd, 0.03% Bi, 0.02% Sr, 0.01% Ca, and 0.05% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0072] The preparation method of the high-strength and high-pressure die-cast magnesium alloy is the same as that in Example 1.

[0073] Comparative Example 1

[0074] A die-cast high-strength magnesium alloy comprises the following components, measured by weight: 5.21% Zn, 8.02% Al, 0.59% La, 1.32% Ce, 0.04% Sm, 0.03% Y, 0.01% Nd, 0.29% Bi, 0.19% Sr, 0.13% Ca, and 0.07% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0075] The preparation method of the die-cast high-strength magnesium alloy is the same as that in Example 1.

[0076] Comparative Example 2

[0077] A die-cast high-strength magnesium alloy comprises the following components, measured by weight: 11.21% Zn, 7.97% Al, 0.62% La, 1.36% Ce, 0.03% Sm, 0.02% Y, 0.02% Nd, 0.28% Bi, 0.21% Sr, 0.15% Ca, and 0.05% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0078] The preparation method of the die-cast high-strength magnesium alloy is the same as that in Example 1.

[0079] Comparative Example 3

[0080] A die-cast high-strength magnesium alloy comprises the following components, measured by weight: 8.05% Zn, 5.11% Al, 0.57% La, 1.28% Ce, 0.05% Sm, 0.03% Y, 0.02% Nd, 0.32% Bi, 0.18% Sr, 0.14% Ca, and 0.06% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0081] The preparation method of the die-cast high-strength magnesium alloy is the same as that in Example 1.

[0082] Comparative Example 4

[0083] A die-cast high-strength magnesium alloy consists of the following components, measured by weight: 8.07% Zn, 10.99% Al, 0.64% La, 1.38% Ce, 0.02% Sm, 0.04% Y, 0.03% Nd, 0.29% Bi, 0.17% Sr, 0.16% Ca, and 0.09% Zr, with the remainder being Mg and unavoidable impurity elements, with the total content of the impurity elements being ≤0.1%.

[0084] The preparation method of the die-cast high-strength magnesium alloy is the same as that in Example 1.

[0085] Comparative Example 5

[0086] A die-cast high-strength magnesium alloy consists of the following components, measured by weight: 8.02% Zn, 7.97% Al, 0.04% Sm, 0.03% Y, 0.02% Nd, 0.33% Bi, 0.2% Sr, 0.13% Ca, and 0.08% Zr, with the remainder being Mg and unavoidable impurity elements, with the total content of the impurity elements being ≤0.1%.

[0087] The preparation method of the die-cast high-strength magnesium alloy is the same as that in Example 1.

[0088] Comparative Example 6

[0089] A die-cast high-strength magnesium alloy consists of the following components, measured by weight: 7.98% Zn, 8.02% Al, 1.54% La, 2.98% Ce, 0.03% Sm, 0.05% Y, 0.01% Nd, 0.35% Bi, 0.19% Sr, 0.12% Ca, and 0.04% Zr, with the remainder being Mg and unavoidable impurity elements, with the total impurity element content being ≤0.1%.

[0090] The preparation method of the die-cast high-strength magnesium alloy is the same as that in Example 1.

[0091] Comparative Example 7

[0092] A die-cast high-strength magnesium alloy consists of the following components, measured by weight: 7.99% Zn, 8.01% Al, 0.7% La, 1.41% Ce, 0.01% Sm, 0.04% Y, 0.02% Nd, with the remainder being Mg and unavoidable impurity elements, with the total content of the impurity elements being ≤0.1%.

[0093] A method for preparing a die-cast high-strength magnesium alloy, comprising the following steps:

[0094] S1. Weigh Mg ingot, Zn ingot, Al ingot and mixed rare earth according to the alloy composition ratio;

[0095] Steps S2-S6 are the same as in Example 1.

[0096] Table 1 shows the alloying element contents of the magnesium alloys in Examples 1-8 and Comparative Examples 1-7.

[0097] Table 2 shows the mechanical properties and hot cracking properties of the magnesium alloys in Examples 1-8 and Comparative Examples 1-7.

[0098] Table 1 Alloying element content (wt.%) of magnesium alloys in Examples 1-8 and Comparative Examples 1-7

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[0101] Table 2 Mechanical properties and hot cracking properties of magnesium alloys in Examples 1-8 and Comparative Examples 1-7

[0102] Tensile strength / MPa Yield strength / MPa Elongation / % Alloy solidification range / ℃ Thermal cracking coefficient Example 1 282 182 5.6 258.35 12 Example 2 287 192 4.7 251.15 12 Example 3 294 209 4.3 238.78 8 Example 4 289 199 5.6 241.05 12 Example 5 295 197 4.6 243.87 12 Example 6 281 181 4.1 238.55 8 Example 7 308 228 4.8 236.67 4 Example 8 290 205 5.3 236.67 4 Comparative Example 1 251 174 5.8 275.63 28 Comparative Example 2 267 169 3.2 282.16 32 Comparative Example 3 248 159 4.1 279.19 32 Comparative Example 4 266 164 4.6 275 28 Comparative Example 5 232 148 4 268.7 20 Comparative Example 6 275 172 5.2 265.12 16 Comparative Example 7 244 157 4.5 267.19 16

[0103] It can be seen from the data in Table 2 that the strength of the die-cast magnesium alloys prepared in Examples 1-8 of the present invention is significantly improved compared with the currently commonly used AZ91D, AM50A, AM60B, etc.

[0104] Comparative Examples 1-4 show that when the Zn and Al content is below the range specified by the present invention, the strength of the alloy decreases. However, the strength of the alloy does not always increase with increasing element content. When the Zn and Al content exceeds the range specified by the present invention, the strength begins to decrease. The hot cracking coefficient shows that excessive Zn exacerbates interdendritic segregation, resulting in poor hot cracking resistance. Furthermore, the Al / Zn ratio significantly affects the mechanical properties of the alloy. When the Zn:Al ratio is close to 1:1, the alloy achieves optimal mechanical properties and the best hot cracking resistance. This is because at this ratio, the MgZn phase, which affects the hot cracking resistance of the alloy, transforms into the ternary AlMgZn phase, which is beneficial for the casting of the magnesium alloy.

[0105] It can be seen from Comparative Examples 5 and 6 that the addition of La / Ce rare earth elements can improve the mechanical properties of magnesium alloys, but too high a rare earth element content will also have a negative impact on the alloy properties. On the one hand, this may be due to the fact that the addition of too many rare earth elements makes the fluidity of the alloy worse, and then during the die-casting process, the slag removal effect does not reach the optimal result. On the other hand, excessive rare earths will cause the brittle phase (such as Mg3RE) to aggregate, which will cause the alloy to become brittle.

[0106] It can be seen from Comparative Example 7 that the mixed addition of Ca, Bi and Sr elements further improves the strength of the alloy.

[0107] Figure 1 Figure 1 shows the factors influencing hot cracking in rods. The difficulty factors for hot cracking are as follows: 4 for the longest rod, 8 for the second longest rod, 16 for the shortest rod, and 32 for the shortest rod. The factors influencing crack location are: cracks are most likely to occur at the root, with a parameter of 1, followed by the ball end, with a parameter of 2, and the middle is least likely to break, with a parameter of 3.

[0108] Figure 2 The figures are the physical images of the hot cracking rods of magnesium alloy in Example 7 and Comparative Example 1, where (a) and (b) are from Example 7, (c) and (d) are from Comparative Example 1, (a) and (c) are the physical images of the hot cracking rods alone, and (b) and (d) are the physical images of the hot cracking rods placed in the mold. Figure 2 It can be seen that compared with Comparative Example 1, Example 7 has fewer cracking locations, with only one cracking location at the bottom of the longest rod, indicating that the hot cracking resistance of Example 7 is significantly better than that of Comparative Example 1.

[0109] Figure 3is the stress-strain curve of the magnesium alloy in Example 7 and Comparative Example 1. Figure 3 It can be seen that the yield strength and tensile strength of Example 7 are significantly higher than those of Comparative Example 1, and its elongation is also comparable to that of Comparative Example 1.

[0110] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-strength and high-pressure die-cast magnesium alloy, characterized in that: Calculated by weight, it is composed of the following components: Zn 6-10%, Al 6-10%, La 0.1-1%, Ce 0.1-2%, Sm 0.001-0.1%, Y0.001-0.1%, Nd 0.001-0.1%, Bi 0.01-0.5%, Sr 0.001-0.3%, Ca 0.001-0.2%, Zr0-0.1%, and the balance is Mg and unavoidable impurity elements.

2. The high-strength and high-pressure die-cast magnesium alloy according to claim 1, characterized in that: Calculated by weight, it is composed of the following components: Zn 6-8%, Al 6-8%, La 0.5-1%, Ce 1-2%, Sm0.01-0.02%, Y 0.01-0.03%, Nd 0.005-0.01%, Bi 0.3-0.4%, Sr 0.2-0.3%, Ca0.08-0.1%, Zr 0-0.08%, and the balance is Mg and unavoidable impurity elements, wherein the total weight of the impurity elements is ≤0.1%.

3. The high-strength and high-pressure die-cast magnesium alloy according to claim 1, characterized in that: Calculated by weight, it is composed of the following components: Zn 8-10%, Al 6-8%, La 0.5-1%, Ce 1-2%, Sm 0.02-0.3%, Y 0.02-0.03%, Nd 0.01-0.02%, Bi 0.2-0.4%, Sr 0.1-0.3%, Ca0.09-0.1%, Zr 0.07-0.09%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%.

4. The high-strength and high-pressure die-cast magnesium alloy according to claim 1, characterized in that: Calculated by weight, it is composed of the following components: Zn 8-10%, Al 8-10%, La 0.5-0.7%, Ce 1.2-1.5%, Sm 0.03-0.04%, Y0.01-0.02%, Nd 0.01-0.02%, Bi 0.1-0.4%, Sr 0.1-0.2%, Ca 0.08-0.1%, Zr 0.06-0.08%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%.

5. The high-strength and high-pressure die-cast magnesium alloy according to claim 1, characterized in that: Calculated by weight, it is composed of the following components: Zn 8-9%, Al 8-9%, La 0.1-0.3%, Ce 0.1-0.8%, Sm 0.02-0.03%, Y0.03-0.04%, Nd 0.01-0.02%, Bi 0.2-0.3%, Sr 0.1-0.2%, Ca0.1-0.15%, Zr 0.06-0.07%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%.

6. The high-strength and high-pressure die-cast magnesium alloy according to claim 1, characterized in that: Calculated by weight, it is composed of the following components: Zn 7-9%, Al 8-9%, La 0.5-0.8%, Ce 1.3-1.6%, Sm 0.02-0.04%, Y0.01-0.02%, Nd 0.02-0.03%, Bi 0.03-0.5%, Sr 0.02-0.3%, Ca 0.01-0.2%, Zr 0.05-0.06%, and the balance is Mg and unavoidable impurity elements, wherein the total content of impurity elements is ≤0.1%.

7. The high-strength and high-pressure die-cast magnesium alloy according to claim 1, characterized in that: The high-strength and high-pressure die-cast magnesium alloy has a tensile strength of 281-308 MPa, a yield strength of 181-228 MPa, an elongation of 4.1-5.6%, an alloy solidification range of 236.67-258.35° C., and a thermal cracking coefficient of 4-12.

8. A method for preparing the high-strength and high-pressure die-cast magnesium alloy according to any one of claims 1 to 7, characterized in that: The following steps are involved: Weighing raw materials according to the alloy composition ratio, and sequentially performing smelting, refining, deslagging and casting to obtain magnesium alloy ingots; The magnesium alloy ingot is die-cast to obtain the high-strength and high-pressure die-cast magnesium alloy.

9. The preparation method according to claim 8, characterized in that The raw materials include Mg ingots, Zn ingots, Al ingots, mixed rare earth, Mg-Ca master alloy, Al-Sr master alloy, Mg-Bi master alloy and Mg-Zr master alloy; and / or, The temperature of the refining and deslagging is 730-760° C., the time is 20-30 minutes, and the amount of the refining agent used is 1-2% of the total mass of the raw materials.

10. The preparation method according to claim 8, characterized in that The die-casting process parameters include: injection pressure of 40±5MPa, injection speed of 5±0.5m / s, magnesium alloy melt temperature of 690±10℃, mold temperature of 200±10℃, mass ratio of release agent to water of 1:80, and atmosphere of a mixed atmosphere of SF6 and N2.

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