High-strength magnesium alloy casting and preparation method and application thereof

Abstract

The invention discloses a high-strength magnesium alloy casting and a preparation method and application thereof, and relates to the technical field of alloy materials, the high-strength magnesium alloy casting is prepared from a magnesium alloy matrix and a reinforcing body distributed in the magnesium alloy matrix, the magnesium alloy matrix comprises the following components in percentage by weight: 0.05-0.5% of Ta, 0.5-2% of Ga, 0.03-0.3% of Co, 0.2-0.8% of Mn, 2-4% of rare earth elements, 0.5-3% of Si, 0.1-0.3% of Sr, 0.8-1.5% of Zn, 0.05-0.2% of Nb, 0.03-0.1% of Mo, 0.06-0.11% of Hf and the balance of magnesium. And the balance of Mg and inevitable impurity elements. The high-strength magnesium alloy casting is good in mechanical property and excellent in corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, and in particular to a high-strength magnesium alloy casting, its preparation method, and its application. Background Technology

[0002] Magnesium alloys, as lightweight and high-strength metallic materials, have shown great application potential in aerospace, automotive manufacturing, and electronic information industries. With the increasing global demand for energy conservation and emission reduction and the continuous development of industry, the market demand for magnesium alloys has been rising year by year, and the performance requirements for magnesium alloy castings are becoming increasingly stringent, especially in terms of strength, requiring them to withstand greater loads and more complex working conditions.

[0003] Traditional magnesium alloy castings often lack the strength required for high-end applications, and are prone to deformation or fracture under heavy loads, limiting their further promotion and application. Current technologies typically improve the strength of magnesium alloys by adding alloying elements such as aluminum, zinc, and manganese. However, simply adding elements is sometimes ineffective, and improper control of element ratios can negatively impact other properties of the magnesium alloy, such as reducing its plasticity and toughness. Furthermore, commercially available magnesium alloy castings often suffer from insufficient corrosion resistance, complex manufacturing processes, low production efficiency, and high costs, hindering large-scale industrial production.

[0004] To address the aforementioned issues, patent document CN116043085B discloses a magnesium-based composite material comprising a magnesium alloy matrix and reinforcements distributed within the magnesium alloy matrix. The magnesium alloy matrix, by weight (100%), comprises the following components in the following weight percentages: Zn 4%-7%, Ca 0.05%-0.8%, Al 0-4%, Zr 0-1%, Ce 0-0.8%, La 0-0.8%, Y 0-0.8%, Nd 0-0.8%, Si 0-0.8%, Mn 0-1.5%, Sr 0-0.5%, Sn 0-1%, Sc 0-0.5%, Gd 0-0.8%, with the balance being Mg and unavoidable impurity elements. This magnesium-based composite material exhibits excellent comprehensive properties, including high thermal conductivity, high strength and toughness, and high modulus, and can be prepared at low cost. The application also provides a method for preparing the magnesium-based composite material and an electronic device using the magnesium-based composite material. However, its mechanical strength and corrosion resistance still need to be further improved. Summary of the Invention

[0005] The main objective of this invention is to overcome the above-mentioned shortcomings and provide a high-strength magnesium alloy casting with good mechanical properties and excellent corrosion resistance, as well as its preparation method and application.

[0006] To achieve the above objectives, the present invention provides a high-strength magnesium alloy casting, which is made of a magnesium alloy matrix and reinforcements distributed in the magnesium alloy matrix. The magnesium alloy matrix comprises the following components by weight percentage: Ta 0.05-0.5%, Ga 0.5-2%, Co 0.03-0.3%, Mn 0.2-0.8%, rare earth elements 2-4%, Si 0.5-3%, Sr 0.1-0.3%, Zn 0.8-1.5%, Nb 0.05-0.2%, Mo 0.03-0.1%, Hf 0.06-0.11%, with the balance being Mg and unavoidable impurity elements.

[0007] Preferably, the rare earth elements are Ce, Sc, Y, and Er mixed in a mass ratio of (3-5):1:1:(0.3-0.5).

[0008] Preferably, the reinforcing body is a mixture of boron nanofibers, vanadium nanocarbide, and niobium nanonitride in a mass ratio of (1-3):(0.8-1.2):(0.5-1).

[0009] Preferably, the average diameter of the boron nanofiber is 30-100 nm, and the aspect ratio is (15-20):1.

[0010] Preferably, the average particle size of the nano-vanadium carbide is 10-60 nm; and the particle size of the nano-niobium nitride is 50-100 nm.

[0011] Preferably, the volume percentage of the reinforcing body is 2%-5%.

[0012] Another object of the present invention is to provide a method for preparing the high-strength magnesium alloy casting, comprising the following steps: Step S1: Obtain magnesium alloy matrix melt by smelting, cool the magnesium alloy melt to 580-600℃ at a rate of 2-3℃ / s, add reinforcement; treat with ultrasonic vibration and spiral stirring for 18-22 minutes to form a semi-solid slurry; Step S2: Preheat the mold to 200-250℃, and inject the semi-solid slurry into the injection chamber at a speed of 0.5-1m / s through a nitrogen-protected screw conveyor system to perform semi-solid injection molding. After opening the mold, a casting blank is obtained. Step S3: The casting blank is subjected to homogenization treatment and aging strengthening treatment in sequence to obtain a high-strength magnesium alloy casting.

[0013] Preferably, the melting temperature in step S1 is 740-760°C.

[0014] Preferably, the frequency of the ultrasonic vibration in step S1 is 20kHz and the power is 250W.

[0015] Preferably, the rotation speed of the spiral stirring in step S1 is 140-160 r / min.

[0016] Preferably, the injection pressure of the semi-solid injection molding in step S2 is 80-120 MPa, the pressure increase rate is 10 MPa / s, the holding pressure is 60-80 MPa, and the holding time is 15-20 seconds.

[0017] Preferably, the homogenization treatment in step S3 is performed at a temperature of 410-430°C for 2 hours, followed by furnace cooling to room temperature.

[0018] Preferably, the aging strengthening treatment in step S3 is performed at a temperature of 158-162°C for 7-9 hours, followed by air cooling to room temperature.

[0019] Another object of the present invention is to provide an application of the high-strength magnesium alloy casting in the housing of a new energy vehicle motor or the landing gear of a drone.

[0020] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The method for preparing high-strength magnesium alloy castings disclosed in this invention is simple, easy to operate, easy to industrialize, has high preparation efficiency, low dependence on equipment, and has high application value.

[0021] (2) The high-strength magnesium alloy casting disclosed in this invention is made of a magnesium alloy matrix and reinforcements distributed in the magnesium alloy matrix. The magnesium alloy matrix comprises the following components by weight percentage: Ta 0.05-0.5%, Ga 0.5-2%, Co 0.03-0.3%, Mn 0.2-0.8%, rare earth elements 2-4%, Si 0.5-3%, Sr 0.1-0.3%, Zn 0.8-1.5%, Nb 0.05-0.2%, Mo 0.03-0.1%, Hf 0.06-0.11%, with the balance being Mg and unavoidable impurity elements. Through the synergistic effect of the components, the resulting casting has good mechanical properties and excellent corrosion resistance.

[0022] (3) The high-strength magnesium alloy castings disclosed in this invention, with their precise proportions and composite addition of rare earth elements (Ce, Sc, Y, Er), can effectively refine the grains and form stable intermetallic compounds (such as Mg). 12 Ce, Mg 24Compounds such as Y5 are dispersed within the grains and at grain boundaries, hindering dislocation movement and thus significantly improving the yield strength and tensile strength of the alloy. Sc, with its powerful solid solution strengthening and precipitation strengthening effects, has become one of the key factors in improving strength. The addition of elements such as Ta, Nb, Mo, and Hf can form extremely fine dispersed phases, further improving the matrix strength through dispersion strengthening mechanisms and pinning grain boundaries to inhibit grain growth. Ga can reduce the stacking fault energy of the magnesium matrix and promote the initiation of non-basal plane slip systems; Co and Mn form Co-Mn intermetallic compounds, inhibiting microcrack propagation at grain boundaries and resolving the industry contradiction of "high strength - low plasticity".

[0023] (4) The high-strength magnesium alloy casting disclosed in this invention uses Mn as a traditional purifying agent and grain refiner, which helps to remove harmful impurities and refine grains, thereby improving the toughness of the alloy to a certain extent. Si and Sr form a modified Mg2Si phase, and Sr can refine the morphology of Mg2Si from coarse needle-like to granular, which retains its strengthening effect and avoids the brittleness problem caused by traditional Si strengthening. The reinforcement formed by mixing nano-boron fiber, nano-vanadium carbide (VC), and nano-niobium nitride (NbN) in a specific mass ratio of (1-3):(0.8-1.2):(0.5-1) forms an efficient composite material system with the magnesium alloy matrix. The nano-boron fiber has extremely high strength and elastic modulus, which can effectively bear the external load and transfer the load to the matrix through the interface, playing a significant strengthening role. The nano-VC and NbN particles further hinder dislocation movement through the dispersion strengthening mechanism, and work synergistically with the strengthening in the matrix to greatly improve the hardness and strength of the overall material. The presence of nano-reinforcement can pin the crack tip, deflect the crack propagation path, and consume more fracture energy, thus contributing positively to improving the fracture toughness of composite materials while increasing strength.

[0024] (5) The high-strength magnesium alloy casting disclosed in this invention achieves simultaneous improvement in corrosion resistance and high strength through triple protection of “rare earth passivation film + high melting point element stable phase + reinforcement physical barrier”; the semi-solid injection molding method is adopted, and the temperature of the semi-solid range is lower than that of full melting casting, which makes the reinforcement more stable; the flow front of the “liquid-solid coexistence” characteristic of the semi-solid slurry is in a laminar flow state, which avoids the turbulent air entrapment of full melting casting, which significantly reduces the porosity and the specific gravity segregation of heavy elements such as Ta and Hf is significantly reduced. Detailed Implementation

[0025] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0026] Example 1: A high-strength magnesium alloy casting, made of a magnesium alloy matrix and reinforcements distributed in the magnesium alloy matrix, wherein the magnesium alloy matrix comprises the following components by weight percentage: Ta 0.05%, Ga 0.5%, Co 0.03%, Mn 0.2%, rare earth elements 2%, Si 0.5%, Sr 0.1%, Zn 0.8%, Nb 0.05%, Mo 0.03%, Hf 0.06%, with the balance being Mg and unavoidable impurity elements; the rare earth elements are Ce, Sc, Y, and Er mixed in a mass ratio of 3:1:1:0.3.

[0027] The reinforcing material is a mixture of boron nanofibers, vanadium nanocarbide, and niobium nanonitride in a mass ratio of 1:0.8:0.5; the average diameter of the boron nanofibers is 30 nm and the aspect ratio is 15:1; the average particle size of the vanadium nanocarbide is 10 nm; the particle size of the niobium nanonitride is 50 nm; and the volume percentage of the reinforcing material is 2%.

[0028] A method for preparing the high-strength magnesium alloy casting includes the following steps: Step S1: Obtain magnesium alloy matrix melt by melting, cool the magnesium alloy melt to 580°C at a rate of 2°C / s, add reinforcement; treat with ultrasonic vibration and spiral stirring for 18 minutes to form a semi-solid slurry; Step S2: Preheat the mold to 200°C, and inject the semi-solid slurry into the injection chamber at a speed of 0.5 m / s through a nitrogen-protected screw conveyor system to perform semi-solid injection molding. After opening the mold, a casting blank is obtained. Step S3: The casting blank is subjected to homogenization treatment and aging strengthening treatment in sequence to obtain a high-strength magnesium alloy casting.

[0029] The melting temperature in step S1 is 740℃; the ultrasonic vibration frequency in step S1 is 20kHz, and the power is 250W; the rotation speed of the spiral stirring in step S1 is 140r / min; the injection pressure of the semi-solid injection molding in step S2 is 80MPa, the pressure increase rate is 10MPa / s, the holding pressure is 60MPa, and the holding time is 15 seconds; the homogenization treatment in step S3 is at a temperature of 410℃, the holding time is 2 hours, and it is cooled to room temperature in the furnace; the aging strengthening treatment in step S3 is at a temperature of 158℃, the holding time is 7 hours, and it is air-cooled to room temperature.

[0030] The application of the high-strength magnesium alloy casting in the housing of a new energy vehicle motor or the landing gear of a drone.

[0031] Example 2: A high-strength magnesium alloy casting, made of a magnesium alloy matrix and reinforcements distributed in the magnesium alloy matrix, wherein the magnesium alloy matrix comprises the following components by weight percentage: Ta 0.15%, Ga 0.8%, Co 0.1%, Mn 0.4%, rare earth elements 2.5%, Si 1%, Sr 0.15%, Zn 1%, Nb 0.1%, Mo 0.05%, Hf 0.08%, with the balance being Mg and unavoidable impurity elements; the rare earth elements are Ce, Sc, Y, and Er mixed in a mass ratio of 3.5:1:1:0.35.

[0032] The reinforcing material is a mixture of boron nanofibers, vanadium nanocarbide, and niobium nanonitride in a mass ratio of 1.5:0.9:0.7; the average diameter of the boron nanofibers is 50 nm and the aspect ratio is 17:1; the average particle size of the vanadium nanocarbide is 30 nm; the particle size of the niobium nanonitride is 70 nm; and the volume percentage of the reinforcing material is 3%.

[0033] A method for preparing the high-strength magnesium alloy casting includes the following steps: Step S1: Obtain magnesium alloy matrix melt by smelting, cool the magnesium alloy melt to 585°C at a rate of 2.3°C / s, add reinforcement; treat with ultrasonic vibration and spiral stirring for 19 minutes to form a semi-solid slurry; Step S2: Preheat the mold to 220°C, and inject the semi-solid slurry into the injection chamber at a speed of 0.7 m / s through a nitrogen-protected screw conveyor system to perform semi-solid injection molding. After opening the mold, a casting blank is obtained. Step S3: The casting blank is subjected to homogenization treatment and aging strengthening treatment in sequence to obtain a high-strength magnesium alloy casting.

[0034] The melting temperature in step S1 is 745℃; the ultrasonic vibration frequency in step S1 is 20kHz, and the power is 250W; the rotation speed of the spiral stirrer in step S1 is 145r / min; the injection pressure of the semi-solid injection molding in step S2 is 90MPa, the pressure increase rate is 10MPa / s, the holding pressure is 65MPa, and the holding time is 17 seconds; the homogenization treatment temperature in step S3 is 415℃, the holding time is 2 hours, and the furnace is cooled to room temperature; the aging strengthening treatment temperature in step S3 is 159℃, the holding time is 7.5 hours, and the furnace is air-cooled to room temperature.

[0035] The application of the high-strength magnesium alloy casting in the housing of a new energy vehicle motor or the landing gear of a drone.

[0036] Example 3: A high-strength magnesium alloy casting, made of a magnesium alloy matrix and reinforcements distributed in the magnesium alloy matrix, wherein the magnesium alloy matrix comprises the following components by weight percentage: Ta 0.35%, Ga 1.3%, Co 0.15%, Mn 0.5%, rare earth elements 3%, Si 1.5%, Sr 0.2%, Zn 1.2%, Nb 0.12%, Mo 0.07%, Hf 0.09%, with the balance being Mg and unavoidable impurity elements; the rare earth elements are Ce, Sc, Y, and Er mixed in a mass ratio of 4:1:1:0.4.

[0037] The reinforcing material is a mixture of boron nanofibers, vanadium nanocarbide, and niobium nanonitride in a mass ratio of 2:1:0.8; the average diameter of the boron nanofibers is 70 nm and the aspect ratio is 18:1; the average particle size of the vanadium nanocarbide is 40 nm; the particle size of the niobium nanonitride is 80 nm; and the volume percentage of the reinforcing material is 3.5%.

[0038] A method for preparing the high-strength magnesium alloy casting includes the following steps: Step S1: Obtain magnesium alloy matrix melt by smelting, cool the magnesium alloy melt to 590°C at a rate of 2.5°C / s, add reinforcement; treat with ultrasonic vibration and spiral stirring for 20 minutes to form a semi-solid slurry; Step S2: Preheat the mold to 230°C, and inject the semi-solid slurry into the injection chamber at a speed of 0.8 m / s through a nitrogen-protected screw conveyor system to perform semi-solid injection molding. After opening the mold, a casting blank is obtained. Step S3: The casting blank is subjected to homogenization treatment and aging strengthening treatment in sequence to obtain a high-strength magnesium alloy casting.

[0039] The melting temperature in step S1 is 750℃; the ultrasonic vibration frequency in step S1 is 20kHz, and the power is 250W; the rotation speed of the spiral stirring in step S1 is 150r / min; the injection pressure of the semi-solid injection molding in step S2 is 100MPa, the pressure increase rate is 10MPa / s, the holding pressure is 70MPa, and the holding time is 18 seconds; the homogenization treatment in step S3 is at a temperature of 420℃, the holding time is 2 hours, and it is cooled to room temperature in the furnace; the aging strengthening treatment in step S3 is at a temperature of 160℃, the holding time is 8 hours, and it is air-cooled to room temperature.

[0040] The application of the high-strength magnesium alloy casting in the housing of a new energy vehicle motor or the landing gear of a drone.

[0041] Example 4: A high-strength magnesium alloy casting, made of a magnesium alloy matrix and reinforcements distributed in the magnesium alloy matrix, wherein the magnesium alloy matrix comprises the following components by weight percentage: Ta 0.45%, Ga 1.8%, Co 0.25%, Mn 0.7%, rare earth elements 3.5%, Si 2.5%, Sr 0.25%, Zn 1.3%, Nb 0.18%, Mo 0.09%, Hf 0.1%, with the balance being Mg and unavoidable impurity elements; the rare earth elements are Ce, Sc, Y, and Er mixed in a mass ratio of 4.5:1:1:0.45.

[0042] The reinforcement is a mixture of boron nanofibers, vanadium nanocarbide, and niobium nanonitride in a mass ratio of 2.5:1.1:0.9; the average diameter of the boron nanofibers is 90 nm and the aspect ratio is 19:1; the average particle size of the vanadium nanocarbide is 50 nm; the particle size of the niobium nanonitride is 90 nm; and the volume percentage of the reinforcement is 4.5%.

[0043] A method for preparing the high-strength magnesium alloy casting includes the following steps: Step S1: Obtain magnesium alloy matrix melt by smelting, cool the magnesium alloy melt to 595°C at a rate of 2.8°C / s, add reinforcement; treat with ultrasonic vibration and spiral stirring for 21 minutes to form a semi-solid slurry; Step S2: Preheat the mold to 240℃, and inject the semi-solid slurry into the injection chamber at a speed of 0.9m / s through a nitrogen-protected screw conveyor system to perform semi-solid injection molding. After opening the mold, a casting blank is obtained. Step S3: The casting blank is subjected to homogenization treatment and aging strengthening treatment in sequence to obtain a high-strength magnesium alloy casting.

[0044] The melting temperature in step S1 is 755℃; the ultrasonic vibration frequency in step S1 is 20kHz, and the power is 250W; the rotation speed of the spiral stirrer in step S1 is 155r / min; the injection pressure of the semi-solid injection molding in step S2 is 110MPa, the pressure increase rate is 10MPa / s, the holding pressure is 75MPa, and the holding time is 19 seconds; the homogenization treatment temperature in step S3 is 425℃, the holding time is 2 hours, and the furnace is cooled to room temperature; the aging strengthening treatment temperature in step S3 is 161℃, the holding time is 8.5 hours, and the furnace is air-cooled to room temperature.

[0045] The application of the high-strength magnesium alloy casting in the housing of a new energy vehicle motor or the landing gear of a drone.

[0046] Example 5: A high-strength magnesium alloy casting, made of a magnesium alloy matrix and reinforcements distributed in the magnesium alloy matrix, wherein the magnesium alloy matrix comprises the following components by weight percentage: Ta 0.5%, Ga 2%, Co 0.3%, Mn 0.8%, rare earth elements 4%, Si 3%, Sr 0.3%, Zn 1.5%, Nb 0.2%, Mo 0.1%, Hf 0.11%, with the balance being Mg and unavoidable impurity elements; the rare earth elements are Ce, Sc, Y, and Er mixed in a mass ratio of 5:1:1:0.5.

[0047] The reinforcing material is a mixture of boron nanofibers, vanadium nanocarbide, and niobium nanonitride in a mass ratio of 3:1.2:1; the average diameter of the boron nanofibers is 100 nm and the aspect ratio is 20:1; the average particle size of the vanadium nanocarbide is 60 nm; the particle size of the niobium nanonitride is 100 nm; and the volume percentage of the reinforcing material is 5%.

[0048] A method for preparing the high-strength magnesium alloy casting includes the following steps: Step S1: Obtain magnesium alloy matrix melt by smelting, cool the magnesium alloy melt to 600°C at a rate of 3°C / s, add reinforcement; treat with ultrasonic vibration and spiral stirring for 22 minutes to form a semi-solid slurry; Step S2: Preheat the mold to 250°C, and inject the semi-solid slurry into the injection chamber at a speed of 1 m / s through a nitrogen-protected screw conveyor system to perform semi-solid injection molding. After opening the mold, a casting blank is obtained. Step S3: The casting blank is subjected to homogenization treatment and aging strengthening treatment in sequence to obtain a high-strength magnesium alloy casting.

[0049] The melting temperature in step S1 is 760℃; the ultrasonic vibration frequency in step S1 is 20kHz, and the power is 250W; the rotation speed of the spiral stirring in step S1 is 160r / min; the injection pressure of the semi-solid injection molding in step S2 is 120MPa, the pressure increase rate is 10MPa / s, the holding pressure is 80MPa, and the holding time is 20 seconds; the homogenization treatment in step S3 is at a temperature of 430℃, the holding time is 2 hours, and it is cooled to room temperature in the furnace; the aging strengthening treatment in step S3 is at a temperature of 162℃, the holding time is 9 hours, and it is air-cooled to room temperature.

[0050] The application of the high-strength magnesium alloy casting in the housing of a new energy vehicle motor or the landing gear of a drone.

[0051] Comparative Example 1 A high-strength magnesium alloy casting, its preparation method and application are basically the same as those in Example 1, except that Ta, Ga and Co are not added.

[0052] Comparative Example 2 A high-strength magnesium alloy casting, its preparation method, and its application are basically the same as those in Example 1, except that Nb, Mo, and Sr are not added.

[0053] To further illustrate the beneficial technical effects of the high-strength magnesium alloy castings involved in the various embodiments of the present invention, relevant performance tests were conducted on the high-strength magnesium alloy castings involved in Example 1 and Comparative Examples 1-2. The test results are shown in Table 1, and the test methods are as follows: (1) Tensile properties: Tested according to GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test method at room temperature", with a specimen size of Φ10mm×50mm; (2) Corrosion resistance: An immersion corrosion test was conducted at room temperature (25℃) using a 15% NaCl solution as the corrosive medium. The corrosion sample was a circular magnesium alloy sample with dimensions of Φ15mm × 3mm; the corrosion test duration was 100 hours. The weight loss of the sample before and after corrosion was measured, and the daily corrosion rate (mg·cm⁻¹) of the magnesium alloy sample was calculated based on the sample's surface area. 2 ·d- 1 ).

[0054] Table 1 Performance test results of high-strength magnesium alloy castings project unit Example 1 Comparative Example 1 Comparative Example 2 tensile strength MPa 385 325 340 Yield strength MPa 305 255 270 elongation % 13 10 11 Corrosion rate <![CDATA[mg·cm -2 ·d -1 ]]> 0.028 0.065 0.037 As can be seen from Table 1, the high-strength magnesium alloy castings disclosed in the embodiments of the present invention have better mechanical properties and superior corrosion resistance than the comparative products; the combined use of Ta, Ga, Co, Nb, Mo and Sr is beneficial to improving the above properties.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A high-strength magnesium alloy casting, characterized in that, It is made of a magnesium alloy matrix and reinforcements distributed in the magnesium alloy matrix, wherein the magnesium alloy matrix comprises the following components in weight percentage: Ta 0.05-0.5%, Ga 0.5-2%, Co 0.03-0.3%, Mn 0.2-0.8%, rare earth elements 2-4%, Si 0.5-3%, Sr 0.1-0.3%, Zn 0.8-1.5%, Nb 0.05-0.2%, Mo 0.03-0.1%, Hf 0.06-0.11%, with the balance being Mg and unavoidable impurity elements.

2. The high-strength magnesium alloy casting according to claim 1, characterized in that, The rare earth elements are Ce, Sc, Y, and Er mixed in a mass ratio of (3-5):1:1:(0.3-0.5).

3. The high-strength magnesium alloy casting according to claim 1, characterized in that, The reinforcement is a mixture of boron nanofibers, vanadium nanocarbide, and niobium nanonitride in a mass ratio of (1-3):(0.8-1.2):(0.5-1).

4. The high-strength magnesium alloy casting according to claim 3, characterized in that, The average diameter of the boron nanofiber is 30-100 nm, and the aspect ratio is (15-20):1; the average particle size of the vanadium nanocarbide is 10-60 nm; and the particle size of the niobium nanonitride is 50-100 nm.

5. The high-strength magnesium alloy casting according to claim 1, characterized in that, The volume percentage of the reinforcing material is 2%-5%.

6. A method for preparing a high-strength magnesium alloy casting according to any one of claims 1-5, characterized in that, Includes the following steps: Step S1: Obtain magnesium alloy matrix melt by smelting, cool the magnesium alloy melt to 580-600℃ at a rate of 2-3℃ / s, add reinforcement; treat with ultrasonic vibration and spiral stirring for 18-22 minutes to form a semi-solid slurry; Step S2: Preheat the mold to 200-250℃, and inject the semi-solid slurry into the injection chamber at a speed of 0.5-1m / s through a nitrogen-protected screw conveyor system to perform semi-solid injection molding. After opening the mold, a casting blank is obtained. Step S3: The casting blank is subjected to homogenization treatment and aging strengthening treatment in sequence to obtain a high-strength magnesium alloy casting.

7. The method for preparing high-strength magnesium alloy castings according to claim 6, characterized in that, The melting temperature in step S1 is 740-760℃; the frequency of the ultrasonic vibration in step S1 is 20kHz and the power is 250W; the rotation speed of the spiral stirring in step S1 is 140-160r / min.

8. The method for preparing high-strength magnesium alloy castings according to claim 6, characterized in that, The semi-solid injection molding process in step S2 has an injection pressure of 80-120 MPa, a pressure increase rate of 10 MPa / s, a holding pressure of 60-80 MPa, and a holding time of 15-20 seconds.

9. The method for preparing high-strength magnesium alloy castings according to claim 6, characterized in that, The homogenization treatment in step S3 is carried out at a temperature of 410-430℃ for 2 hours, followed by furnace cooling to room temperature; the aging strengthening treatment in step S3 is carried out at a temperature of 158-162℃ for 7-9 hours, followed by air cooling to room temperature.

10. The application of a high-strength magnesium alloy casting according to any one of claims 1-5 in the housing of a new energy vehicle motor or the landing gear of a drone.