Aluminum alloy for preparing center pin of external bogie of train and preparation method of aluminum alloy

Abstract

The invention discloses an aluminum alloy for preparing a center pin of an external bogie of a train and a preparation method of the aluminum alloy, and belongs to the technical field of aluminum alloy materials. The aluminum alloy for preparing the center pin of the external bogie of the train, provided by the invention, comprises the following components in percentage by weight: 5.8 to 8.0 percent of Zn, 1.5 to 2.7 percent of Mg, 1.5 to 3.0 percent of Cu, 0.07 to 0.35 percent of Zr, 0.04 to 0.2 percent of Ti, 0.04 to 0.2 percent of Mn, 0.05 to 0.5 percent of Nd, 0.1 to 0.3 percent of Sr, 0.1 to 0.3 percent of Sc and the balance of Al and inevitable impurities. Compared with steel, the aluminum alloy for preparing the center pin of the external bogie of the train has the advantages that the weight can be reduced by 40% or above, the excellent mechanical property and fatigue resistance are achieved, and the high-bearing requirement and the light weight of the bogie can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy materials, and particularly relates to an aluminum alloy used for preparing a center pin of an external train bogie and a preparation method thereof. Background Art

[0002] With the gradual increase in the speed of high-speed trains and the important demand for energy conservation and environmental protection, the performance requirements for the support seats of key components of high-speed trains are also increasing. Meeting the high-standard mechanical performance requirements of the support seats while achieving weight reduction is a major reform and structural adjustment faced by the development of high-speed trains. The implementation of speed-up and safe development technologies requires in-depth structural optimization and component lightweighting of support seat products. The center pins of the external bogies of the currently operating high-speed trains are mainly steel structures, resulting in a high overall quality of the external bogie center pin body, which has seriously affected the high-speed requirements of the trains. Aluminum alloy, as a lightweight structural material, has the advantages of low density, high strength, good electrical and thermal conductivity, good corrosion resistance, easy forming and processing, and has been widely used in the manufacturing field of high-speed trains. However, the mechanical properties of existing aluminum alloys are poor, and its performance is difficult to meet the requirements of the center pins of the external bogies of high-speed trains. Summary of the invention

[0003] In view of the deficiencies in the prior art, the object of the present invention is to provide an aluminum alloy for preparing a center pin of an external train bogie and a preparation method thereof, so as to solve the problem in the prior art that the center pin of an external high-speed train bogie is difficult to achieve both lightweight and high load-bearing requirements.

[0004] The technical solution of the present invention to solve the above technical problems is as follows: an aluminum alloy for preparing a center pin of an external train bogie is provided, comprising the following components in weight percentage: 5.8-8.0% Zn, 1.5-2.7% Mg, 1.5-3.0% Cu, 0.07-0.35% Zr, 0.04-0.2% Ti, 0.04-0.2% Mn, 0.05-0.5% Nd, 0.1-0.3% Sr, 0.1-0.3% Sc, and the rest is Al and unavoidable impurities.

[0005] The beneficial effects of the present invention are as follows: Zn forms strengthening phases such as MgZn2 in the aluminum matrix to hinder dislocation movement and enhance the strength and hardness of the alloy; Mg forms a solid solution in the aluminum matrix to increase the strength of the material, and at the same time Mg reacts with Zn to form a MgZn2 precipitation phase, further improving the strength and fatigue resistance of the alloy; Cu precipitates strengthening phases such as Al2Cu in the alloy to hinder dislocation movement, thereby significantly improving the mechanical properties of the alloy, and Cu also forms an Al2CuMg strengthening phase with Mg to enhance the precipitation strengthening effect; Ti can form phases such as Al3Ti in the aluminum matrix to promote heterogeneous nucleation, and these fine phases can effectively refine the grains, increase the grain boundary area, and hinder dislocation movement, thereby improving the strength and fatigue resistance of the alloy, and at the same time the solid solution strengthening effect of Ti also helps to improve the overall performance of the alloy; Mn forms a stable phase with impurity elements in the aluminum matrix, such as Al6Mn, to prevent impurities from precipitating at the grain boundaries, reduce brittleness, and improve the ductility of the alloy.

[0006] The addition of trace amounts of Nd forms the Al8Cu4Nd phase, which is refined during the superplastic forging process, refining the grains, increasing the grain boundary area, hindering dislocation movement, and further enhancing the mechanical properties and fatigue resistance of the alloy. At the same time, the Nd element will also form Al3Nd particles, which pin dislocations and accelerate the aging process of the alloy.

[0007] Sr and Zr will form Al3Zr particles, which will have the effect of grain refinement in the matrix and enhance the fatigue resistance and ductility of the material. Sr can change the impurity phase distribution in the material and reduce the stress concentration effect by refining the grains, thereby improving the crack resistance and enhancing the mechanical properties and overall stability of the alloy.

[0008] The main precipitation phases formed by Sc and Zr in aluminum alloys are Al3Sc and Al3Zr, which improve the yield strength of the alloy by hindering dislocation movement. At the same time, Sc and Zr will also combine to form a composite phase Al3 (Sc, Zr), which is evenly distributed in the aluminum matrix, improving the thermal stability and mechanical properties of the alloy, so that the aluminum alloy has better strength and toughness in high-performance applications.

[0009] On the basis of the above technical solution, the present invention can also be improved as follows:

[0010] Further, the following components are included in weight percentage: 6.3% Zn, 1.8% Mg, 2.5% Cu, 0.2% Zr, 0.15% Ti, 0.1% Mn, 0.2% Nd, 0.2% Sr, 0.2% Sc, and the remainder is Al and inevitable impurities.

[0011] The present invention also provides a method for preparing the aluminum alloy for preparing the center pin of an external train bogie, comprising the following steps:

[0012] S1. Molten casting: The raw materials are configured according to the mass percentage of each element in the aluminum alloy, and the raw materials are melted and cast to obtain an alloy ingot;

[0013] S2. Multi-stage homogenization treatment: heat the alloy ingot to 380-450°C for 8-14 hours, then heat to 450-490°C for 20-26 hours, and cool with water at room temperature;

[0014] S3. Hot extrusion: The homogenized ingot is heated to 380-450°C for 2-6 hours, and hot extrusion is performed, with an extrusion ratio of ≥10 and a preheating temperature of the extrusion barrel of 380-450°C to obtain an extruded billet;

[0015] S4. Surface treatment and preheating: The extruded billet is ball-milled and polished, and then heated to 380-450° C. for 2-6 hours to obtain a preheated alloy billet;

[0016] S5. Superplastic die forging: The preheated alloy billet is placed in a die for superplastic die forging. The die preheating temperature is 380-450°C, the die forging temperature is 380-450°C, and the die forging rate is 10×10 -5 Up to 10×10 -2 mm / s, and obtain the pre-forged billet;

[0017] S6. Superplastic die forging final forging: Place the pre-forged billet in the die for superplastic die forging final forging. The die preheating temperature is 380-450℃, the die forging temperature is 380-450℃, and the die forging rate is 10×10 -5 Up to 10×10 -2 mm / s, and the final forging billet is obtained;

[0018] S7. Staged heat treatment: heat the final forging billet to 450-500℃ and keep it for 2-6h, then cool it with water at room temperature, then heat it to 110-140℃ and keep it for 18-26h, and then cool it in air;

[0019] S8. Laser surface strengthening: The final forging billet after the segmented heat treatment is subjected to laser surface strengthening treatment, with a laser power of 300 to 700 W, a scanning speed of 1.5 to 3 m / min, a spot diameter of 2 to 6 mm, and an overlap rate of 40%.

[0020] The beneficial effects of adopting the above technical scheme are as follows: multi-stage homogenization treatment and a higher extrusion ratio ensure the grain refinement of the alloy, improve the overall mechanical properties of the material, and make it have stronger crack resistance under multi-directional stress; surface ball milling and polishing treatment strengthens the surface of the aluminum alloy material, uses compressive stress to reduce surface defects, and improves surface fatigue strength and wear resistance; multi-stage heat treatment controls the grain structure through a combination of high-temperature annealing and low-temperature aging heat treatment, avoids stress concentration, and achieves a balance between material strength and toughness; the present invention also adopts two-step superplastic die forging to ensure that the die forging temperature is above the dynamic recrystallization temperature, so that dynamic recrystallization occurs during the die forging process, resulting in grain refinement and equiaxed, which is beneficial to further forming and improving the final mechanical properties; laser surface strengthening significantly improves fatigue resistance and increases the service life of the material by introducing high-pressure residual stress.

[0021] On the basis of the above technical solution, the present invention can also be improved as follows:

[0022] Further, the raw materials include aluminum ingots, Al-Zr master alloys, Al-Mn master alloys, Al-Ti master alloys, Al-Nd master alloys, Al-Sr master alloys, Al-Sc master alloys, zinc ingots and magnesium ingots.

[0023] Further, the specific steps of step S1 molten casting are: heating the aluminum ingot until it is melted, raising the temperature of the melt to 680-700°C, and adding Al-Cu master alloy; continuing to raise the melt temperature to 720-740°C, adding Al-Zr master alloy, Al-Ti master alloy, Al-Mn master alloy, Al-Nd master alloy, Al-Sr master alloy and Al-Sc master alloy; then reducing the melt temperature to 690-710°C, adding zinc ingot and magnesium ingot; then heating the melt to 720-730°C, stirring, standing, and when the melt temperature drops to 710-720°C, pouring to obtain alloy ingot.

[0024] Furthermore, the alloy ingot is descaled before the S2 multi-stage homogenization step.

[0025] Furthermore, the parameters of the ball milling and polishing process in the surface treatment and preheating in step S4 are as follows: the diameter of the grinding balls is 5 to 15 mm, the ball milling pressure is 10 to 30 MPa, the rotation speed is 300 to 800 rpm, and the ball milling time is 10 to 30 min.

[0026] Furthermore, in the superplastic die forging pre-forging in step S5 and the superplastic die forging final forging in step S6, the die preheating temperature is 400°C and the die forging temperature is 400°C.

[0027] Furthermore, in step S7, in the staged heat treatment, the final forging billet is heated to 480° C. and kept at this temperature for 4 hours, then water-cooled at room temperature, and then heated to 130° C. and kept at this temperature for 24 hours, and then air-cooled.

[0028] Furthermore, in step S8, the wavelength of the laser beam in the laser surface strengthening is 1064 nm.

[0029] The present invention has the following beneficial effects:

[0030] 1. The aluminum alloy center pin of the external bogie of a high-speed train provided by the present invention can significantly reduce the mass of the external bogie center pin, and the weight reduction can reach more than 40%.

[0031] 2. The aluminum alloy center pin of the external bogie of a high-speed train provided by the present invention achieves a dual improvement in fatigue resistance and lightweight through the comprehensive coordination of multiple elements and the use of multiple mechanisms such as solid solution strengthening, precipitation strengthening, grain refinement and composite strengthening. The fatigue limit can reach more than 230MPa, and through synergistic effects, the microstructure and mechanical properties are further optimized, which can meet the high load-bearing requirements and lightweight of the bogie. DETAILED DESCRIPTION

[0032] The principles and features of the present invention are described below in conjunction with the examples, which are only used to explain the present invention and are not intended to limit the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0033] Embodiment 1:

[0034] An aluminum alloy for preparing a center pin of an outboard train bogie comprises the following components in weight percentage: 6.3% Zn, 1.8% Mg, 2.5% Cu, 0.2% Zr, 0.15% Ti, 0.1% Mn, 0.2% Nd, 0.2% Sr, 0.2% Sc, and the remainder is Al and unavoidable impurities.

[0035] The method for preparing the aluminum alloy for preparing the center pin of the external bogie of a train comprises the following steps:

[0036] S1. Melt casting: put an aluminum ingot into a crucible and heat it until it melts, then continue to heat it to 680°C, and add Al-Cu master alloy; raise the melt temperature to 725°C, and add Al-Zr master alloy, Al-Ti master alloy, Al-Mn master alloy, Al-Nd master alloy, Al-Sr master alloy, and Al-Sc master alloy in sequence; then lower the melt temperature to 700°C, add zinc ingot and magnesium ingot; then raise the melt temperature to 720°C, stir for 4 minutes, and then stand for 8 minutes. When the temperature drops to 715°C, cast it to obtain an alloy ingot;

[0037] S2. Multi-stage homogenization treatment: remove the outer skin of the alloy ingot, heat to 410℃ and keep it for 8h, then heat to 460℃ and keep it for 24h, and cool it with water at room temperature;

[0038] S3. Hot extrusion: The homogenized ingot was heated to 420°C for 4h and hot extruded with an extrusion ratio of 15 and a preheating temperature of the extrusion barrel of 410°C to obtain an extruded billet;

[0039] S4. Surface treatment and preheating: The extruded billet was ball-milled and polished, with a grinding ball diameter of 10 mm, a ball milling pressure of 30 MPa, a rotation speed of 500 rpm, and a ball milling time of 20 min, and then heated to 430 ° C for 4 h to obtain a preheated alloy billet;

[0040] S5. Superplastic die forging: The preheated alloy billet is placed in a die for superplastic die forging. The die preheating temperature is 400°C, the die forging temperature is 400°C, and the die forging rate is 10×10 -3 mm / s, and obtain the pre-forged billet;

[0041] S6. Superplastic die forging final forging: The pre-forged billet is placed in the die for superplastic die forging final forging. The die preheating temperature is 400℃, the die forging temperature is 400℃, and the die forging rate is 10×10 -3 mm / s, and the final forging billet is obtained;

[0042] S7. Staged heat treatment: heat the final forging billet to 460°C for 4 hours, then cool it with water at room temperature, then heat it to 130°C for 20 hours, and then cool it in air;

[0043] S8. Laser surface strengthening: The final forging billet after the segmented heat treatment is subjected to laser surface strengthening treatment, using a laser beam with a wavelength of 1064nm, a laser power of 500W, a scanning speed of 2m / min, a spot diameter of 3mm, and an overlap rate of 40%.

[0044] Embodiment 2:

[0045] An aluminum alloy for preparing a center pin of an outboard train bogie comprises the following components in weight percentage: 6.8% Zn, 2% Mg, 2.3% Cu, 0.15% Zr, 0.16% Ti, 0.12% Mn, 0.15% Nd, 0.18% Sr, 0.15% Sc, and the remainder is Al and unavoidable impurities.

[0046] The method for preparing the aluminum alloy for preparing the center pin of the external bogie of a train comprises the following steps:

[0047] S1. Melt casting: put an aluminum ingot into a crucible and heat it until it melts, then continue to heat it to 700°C, and add Al-Cu master alloy; raise the melt temperature to 725°C, and add Al-Zr master alloy, Al-Ti master alloy, Al-Mn master alloy, Al-Nd master alloy, Al-Sr master alloy, and Al-Sc master alloy in sequence; then lower the melt temperature to 690°C, add zinc ingot and magnesium ingot; then raise the melt temperature to 720°C, stir for 4 minutes, and then stand for 8 minutes. When the temperature drops to 715°C, cast it to obtain an alloy ingot;

[0048] S2. Multi-stage homogenization treatment: remove the outer skin of the alloy ingot, heat to 450°C for 10 hours, then heat to 450°C for 23 hours, and cool with water at room temperature;

[0049] S3. Hot extrusion: The homogenized ingot was heated to 420°C for 5h and hot extruded with an extrusion ratio of 12 and a preheating temperature of the extrusion barrel of 430°C to obtain an extruded billet;

[0050] S4. Surface treatment and preheating: The extruded billet was ball-milled and polished, with a ball diameter of 10 mm, a ball milling pressure of 30 MPa, a rotation speed of 500 rpm, and a ball milling time of 15 min, and then heated to 430 ° C for 4 h to obtain a preheated alloy billet;

[0051] S5. Superplastic die forging: The preheated alloy billet is placed in a die for superplastic die forging. The die preheating temperature is 450°C, the die forging temperature is 450°C, and the die forging rate is 10×10 -5 mm / s, and obtain the pre-forged billet;

[0052] S6. Superplastic die forging final forging: The pre-forged billet is placed in the die for superplastic die forging final forging. The die preheating temperature is 450℃, the die forging temperature is 450℃, and the die forging rate is 10×10 -5 mm / s, and the final forging billet is obtained;

[0053] S7. Staged heat treatment: heat the final forging billet to 480°C for 4 hours, then cool it with water at room temperature, then heat it to 130°C for 24 hours, and then cool it in air;

[0054] S10. Laser surface strengthening: The final forging billet after the segmented heat treatment is subjected to laser surface strengthening treatment, using a laser beam with a wavelength of 1064nm, a laser power of 500W, a scanning speed of 2m / min, a spot diameter of 3mm, and an overlap rate of 40%.

[0055] Embodiment 3:

[0056] An aluminum alloy for preparing a center pin of an outboard train bogie comprises the following components in weight percentage: 7.1% Zn, 2.3% Mg, 1.8% Cu, 0.15% Zr, 0.16% Ti, 0.12% Mn, 0.15% Nd, 0.18% Sr, 0.17% Sc, and the remainder is Al and unavoidable impurities.

[0057] The method for preparing the aluminum alloy for preparing the center pin of the external bogie of a train comprises the following steps:

[0058] S1. Melt casting: put an aluminum ingot into a crucible and heat it until it melts, then continue to heat it to 700°C, and add Al-Cu master alloy; raise the melt temperature to 725°C, and add Al-Zr master alloy, Al-Ti master alloy, Al-Mn master alloy, Al-Nd master alloy, Al-Sr master alloy, and Al-Sc master alloy in sequence; then lower the melt temperature to 690°C, add zinc ingot and magnesium ingot; then raise the melt temperature to 720°C, stir for 4 minutes, and then stand for 8 minutes. When the temperature drops to 715°C, cast it to obtain an alloy ingot;

[0059] S2. Multi-stage homogenization treatment: remove the outer skin of the alloy ingot, heat to 450°C for 10 hours, then heat to 450°C for 23 hours, and cool with water at room temperature;

[0060] S3. Hot extrusion: The homogenized ingot is heated to 420°C for 5 hours, and hot extrusion is performed at a high extrusion ratio (≥10). The preheating temperature of the extrusion barrel is 430°C to obtain an extruded billet;

[0061] S4. Surface treatment and preheating: The extruded billet was ball-milled and polished, with a grinding ball diameter of 10 mm, a ball milling pressure of 30 MPa, a rotation speed of 500 rpm, and a ball milling time of 20 min, and then heated to 430 ° C for 4 h to obtain a preheated alloy billet;

[0062] S5. Superplastic die forging: The preheated alloy billet is placed in a die for superplastic die forging. The die preheating temperature is 450°C, the die forging temperature is 450°C, and the die forging rate is 10×10 -4 mm / s, and obtain the pre-forged billet;

[0063] S6. Superplastic die forging final forging: The pre-forged billet is placed in the die for superplastic die forging final forging. The die preheating temperature is 450℃, the die forging temperature is 450℃, and the die forging rate is 10×10 -4 mm / s, and the final forging billet is obtained;

[0064] S7. Staged heat treatment: heat the final forging billet to 480°C for 4 hours, then cool it with water at room temperature, then heat it to 130°C for 24 hours, and then cool it in air;

[0065] S8. Laser surface strengthening: The final forging billet after the segmented heat treatment is subjected to laser surface strengthening treatment, using a laser beam with a wavelength of 1064nm, a laser power of 500W, a scanning speed of 2m / min, a spot diameter of 3mm, and an overlap rate of 40%.

[0066] Comparative Example 1:

[0067] An aluminum alloy for preparing a center pin of an outboard train bogie comprises the following components in weight percentage: 6.3% Zn, 1.8% Mg, 2.5% Cu, 0.2% Zr, 0.15% Ti, 0.1% Mn, 0.2% Nd, and the remainder being Al and unavoidable impurities.

[0068] The preparation method of the above-mentioned aluminum alloy used for preparing the center pin of the train external bogie is the same as that in Example 1.

[0069] Comparative Example 2:

[0070] An aluminum alloy for preparing a center pin of an outboard train bogie comprises the following components in weight percentage: 6.3% Zn, 1.8% Mg, 2.5% Cu, 0.2% Zr, 0.15% Ti, 0.1% Mn, 0.2% Nd, 0.2% Sr, 0.2% Sc, and the remainder is Al and unavoidable impurities.

[0071] The difference between the above-mentioned method for preparing the aluminum alloy for preparing the center pin of the external train bogie and the method of Example 1 is that the die forging temperature of the step S5 superplastic die forging pre-forging and the step S6 superplastic die forging final forging is 480°C.

[0072] Comparative Example 3:

[0073] An aluminum alloy for preparing a center pin of an outboard train bogie comprises the following components in weight percentage: 6.3% Zn, 1.8% Mg, 2.5% Cu, 0.2% Zr, 0.15% Ti, 0.1% Mn, 0.2% Nd, 0.2% Sr, 0.2% Sc, and the remainder is Al and unavoidable impurities.

[0074] The difference between the above-mentioned method for preparing the aluminum alloy for preparing the center pin of the external train bogie and the method for preparing the embodiment 1 is that step S4 only performs preheating and omits the process of surface ball milling and polishing.

[0075] Comparative Example 4:

[0076] An aluminum alloy for preparing a center pin of an outboard train bogie comprises the following components in weight percentage: 6.3% Zn, 1.8% Mg, 2.5% Cu, 0.2% Zr, 0.15% Ti, 0.1% Mn, 0.2% Nd, 0.2% Sr, 0.2% Sc, and the remainder is Al and unavoidable impurities.

[0077] The difference between the above-mentioned method for preparing the aluminum alloy for preparing the center pin of the outboard train bogie and the method for preparing the embodiment 1 is that step S8 laser surface strengthening is omitted.

[0078] Experimental example:

[0079] The aluminum alloys prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to rough machining and fine machining according to the center pin rough machining drawings and center pin fine machining drawings to prepare aluminum alloy center pins, and then subjected to mechanical property testing and fatigue testing. The fatigue test parameters were as follows: stress ratio of 0.1, vibration frequency of 60-70 Hz, and number of cycles of 1×10 7 ; At the same time, the weight of the currently used steel center pin is used as a comparison to calculate the weight reduction index. The specific test results are shown in Table 1:

[0080] Table 1 Performance indexes of center pins obtained in each experimental group

[0081]

[0082] It can be seen from the data in Table 1 that compared with comparative examples 1-4, the aluminum-based alloy center pin prepared in Examples 1-3 has significantly improved mechanical properties and fatigue strength, and the degree of lightweight remains basically unchanged, which can meet the performance requirements of the center pin of the high-speed train bogie.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An aluminum alloy for preparing a center pin of an external bogie of a train, characterized in that: The invention comprises the following components in weight percentage: 5.8-8.0% Zn, 1.5-2.7% Mg, 1.5-3.0% Cu, 0.07-0.35% Zr, 0.04-0.2% Ti, 0.04-0.2% Mn, 0.05-0.5% Nd, 0.1-0.3% Sr, 0.1-0.3% Sc, and the rest are Al and inevitable impurities.

2. The aluminum alloy for preparing the center pin of an external train bogie according to claim 1, characterized in that: The alloy comprises the following components in weight percentage: 6.3% Zn, 1.8% Mg, 2.5% Cu, 0.2% Zr, 0.15% Ti, 0.1% Mn, 0.2% Nd, 0.2% Sr, 0.2% Sc, and the rest are Al and inevitable impurities.

3. The method for preparing the aluminum alloy for preparing the center pin of the external train bogie according to claim 1 or 2, characterized in that: The following steps are involved: S1. Melting and pouring: configuring raw materials according to the mass percentage of each element in the aluminum alloy, and melting and pouring the raw materials to obtain an alloy ingot; S2. Multi-stage homogenization treatment: heat the alloy ingot to 380-450°C for 8-14 hours, then heat to 450-490°C for 20-26 hours, and cool with water at room temperature; S3. Hot extrusion: The homogenized ingot is heated to 380-450°C for 2-6 hours, and hot extrusion is performed, with an extrusion ratio of ≥10 and a preheating temperature of the extrusion barrel of 380-450°C to obtain an extruded billet; S4. Surface treatment and preheating: The extruded billet is ball-milled and polished, and then heated to 380-450° C. for 2-6 hours to obtain a preheated alloy billet; S5. Superplastic die forging: The preheated alloy billet is placed in a die for superplastic die forging. The die preheating temperature is 380-450°C, the die forging temperature is 380-450°C, and the die forging rate is 10×10 -5 Up to 10×10 -2 mm / s, and obtain the pre-forged billet; S6. Superplastic die forging final forging: Place the pre-forged billet in the die for superplastic die forging final forging. The die preheating temperature is 380-450℃, the die forging temperature is 380-450℃, and the die forging rate is 10×10 -5 Up to 10×10 -2 mm / s, and the final forging billet is obtained; S7. Staged heat treatment: heat the final forging billet to 450-500℃ and keep it for 2-6h, then cool it with water at room temperature, then heat it to 110-140℃ and keep it for 18-26h, and then cool it in air; S8. Laser surface strengthening: The final forging billet after the segmented heat treatment is subjected to laser surface strengthening treatment, with a laser power of 300 to 700 W, a scanning speed of 1.5 to 3 m / min, a spot diameter of 2 to 6 mm, and an overlap rate of 40%.

4. The preparation method according to claim 3, characterized in that: The raw materials include aluminum ingots, Al-Zr master alloys, Al-Ti master alloys, Al-Mn master alloys, Al-Nd master alloys, Al-Sr master alloys, Al-Sc master alloys, zinc ingots and magnesium ingots.

5. The preparation method according to claim 4, characterized in that: The specific steps of step S1 molten casting are: heating the aluminum ingot to melt, raising the temperature of the melt to 680-700°C, and adding Al-Cu master alloy; continuing to raise the melt temperature to 720-740°C, adding Al-Zr master alloy, Al-Ti master alloy, Al-Mn master alloy, Al-Nd master alloy, Al-Sr master alloy and Al-Sc master alloy; then reducing the melt temperature to 690-710°C, adding zinc ingot and magnesium ingot; and then heating the melt to 720-730°C, stirring, standing, and when the melt temperature drops to 710-720°C, pouring to obtain alloy ingot.

6. The preparation method according to claim 3, characterized in that: The alloy ingot is descaled before the S2 multi-stage homogenization step.

7. The preparation method according to claim 3, characterized in that: The parameters of the ball milling and polishing process in the surface treatment and preheating in step S4 are as follows: the diameter of the grinding balls is 5 to 15 mm, the ball milling pressure is 10 to 30 MPa, the rotation speed is 300 to 800 rpm, and the ball milling time is 10 to 30 min.

8. The preparation method according to claim 3, characterized in that: In the superplastic die forging pre-forging in step S5 and the superplastic die forging final forging in step S6, the die preheating temperature is 400°C and the die forging temperature is 400°C.

9. The preparation method according to claim 3, characterized in that: In step S7, in the staged heat treatment, the final forging billet is heated to 480°C and kept at this temperature for 4 hours, then water-cooled at room temperature, and then heated to 130°C and kept at this temperature for 24 hours, and then air-cooled.

10. The preparation method according to claim 3, characterized in that: The wavelength of the laser beam in the laser surface strengthening step S8 is 1064 nm.

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