Aluminum alloy for preparing traction rod of external bogie of train and preparation method of aluminum alloy

Abstract

The invention discloses an aluminum alloy for preparing a traction rod of an external bogie of a train and a preparation method of the aluminum alloy, and belongs to the field of alloy manufacturing. The aluminum alloy comprises chemical elements in percentage by mass as follows: 5.8%-8.0% of Zn, 1.1%-3.2% of Mg, 1.3%-3.0% of Cu, 0.07%-0.35% of Zr, 0.08%-0.2% of Ti, 0.04%-0.2% of Mn, 0.05%-0.3% of Y, 2.2%-3.6% of Ni, 4.5%-5.5% of Si, 0.02%-0.1% of Nb and the balance of Al. According to the preparation method, an aluminum alloy casting blank is poured according to the mass percent of aluminum alloy elements, then the aluminum alloy casting blank is subjected to homogenization treatment, hot extrusion treatment, superplastic die forging treatment and heat treatment, the aluminum alloy for preparing the traction rod of the train external bogie is obtained, and the fatigue strength of the aluminum alloy can reach 200-230 MPa.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy manufacturing, and in particular relates to an aluminum alloy for preparing a traction rod of an external bogie of a train and a preparation method thereof. Background Art

[0002] With the gradual increase in the operating speed of high-speed trains and the important demand for energy conservation and environmental protection, the further lightweighting of high-speed trains has become a basic element in the design and manufacture of high-speed trains, and is also an inevitable trend.

[0003] The aluminum alloy traction rods of the external bogies of the currently operating high-speed trains are mainly made of ductile iron, resulting in a relatively high overall mass of the bogies. As a lightweight structural material, aluminum alloy has the advantages of low density, high strength, good electrical and thermal conductivity, good corrosion resistance, and easy forming and processing, and has been widely used in the manufacturing field of high-speed trains. The existing high-speed train traction rods use aluminum alloys to reduce the mass of the traction rods to achieve satisfactory lightweight, but their performance is difficult to meet the high requirements of high-speed train traction rods. Summary of the invention

[0004] In view of the above-mentioned prior art, the present invention provides an aluminum alloy for preparing a traction rod of an outboard train bogie and a preparation method thereof, thereby obtaining an aluminum alloy with a fatigue strength of up to 200 to 230 MPa.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: to provide an aluminum alloy for preparing a traction rod of an external bogie of a train, the mass percentage of chemical elements in the aluminum alloy is: 5.8-8.0% Zn, 1.1-3.2% Mg, 1.3-3.0% Cu, 0.07-0.35% Zr, 0.08-0.2% Ti, 0.04-0.2% Mn, 0.05-0.3% Y, 2.2-3.6% Ni, 4.5-5.5% Si and 0.02-0.1% Nb, and the rest is Al.

[0006] The beneficial effects of the present invention are as follows: the chemical composition of the aluminum alloy is Al, Zn, Mg, Cu, Zr, Ti, Mn, Y, Ni, Si and Nb elements, and the various types of second phases existing in the microstructure of the aluminum alloy of the present invention include: MgZn2, Al3Zr, Al 20Ti2Y, Al8Cu4Y, Al3(Zr, Ti) and other phases. Among them, the Al8Cu4Y phase formed by the addition of trace Y is refined during the superplastic die forging process. Part of it is dispersed in the matrix in a granular morphology, and the other part is distributed in a large number of subgrain boundaries in the fine matrix grains of the alloy in a network morphology, which is beneficial to the improvement of the strength performance of the alloy. In addition, the Y element will also form Al3Y particles, which will accelerate the aging process of the alloy while pinning dislocations; the addition of Ti and Mg elements can change the crystal structure of the aluminum alloy and effectively improve the fatigue resistance; and Nb elements and Ti elements can form a γ' precipitation phase together, which can enhance the high temperature strength and fatigue resistance of the alloy, and Nb elements can form a Some fine granular substances can fill the lattice gaps in aluminum alloys and increase the density and hardness of the material; Ni elements can work synergistically with elements such as Al and Nb to form intermetallic compounds such as NiAl3 in aluminum alloys. These compounds can effectively enhance the hardness of the alloy, giving the alloy excellent high-temperature strength, good welding performance and fatigue resistance; Si elements can form a metastable Al-Si phase with Al, which can effectively improve the yield strength and tensile strength of the alloy. Si can also form a silicate phase with Al, which can hinder the corrosion of corrosive media on aluminum alloys, thereby improving the corrosion resistance of the alloy. In addition, aluminum alloys are prone to problems such as grain growth and phase change at high temperatures, resulting in reduced strength and hardness of the material. The addition of Si can inhibit the growth of grains and the occurrence of phase change, stabilize the organizational structure and performance of aluminum alloys, and thus improve the material's bearing capacity and service life.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Further, the mass percentages of chemical elements in the aluminum alloy are: 6.9% Zn, 2.1% Mg, 2.3% Cu, 0.22% Zr, 0.13% Ti, 0.14% Mn, 0.18% Y, 2.9% Ni, 5.0% Si and 0.06% Nb, and the rest is Al.

[0009] The beneficial effect of adopting the further technical solution is that the optimal element mass ratio makes the obtained aluminum alloy have excellent properties.

[0010] The present invention also discloses a method for preparing an aluminum alloy for preparing a traction rod of an external bogie of a train, comprising the following steps:

[0011] S1: pouring aluminum alloy ingots according to the mass percentage of the elements of the aluminum alloy;

[0012] S2: homogenizing the aluminum alloy ingot;

[0013] S3: hot extruding the aluminum alloy ingot after homogenization to obtain an extruded ingot;

[0014] S4: preheating the extruded billet and then sequentially performing superplastic die forging pre-forging and superplastic die forging final forging to obtain a crude product;

[0015] S5: The crude product is heated to 440-500° C. and kept at this temperature for 2-10 hours, and then water-cooled at room temperature; then heated to 110-150° C. and kept at this temperature for 9-26 hours, and air-cooled to obtain an aluminum alloy for preparing a traction rod of an external bogie of a train.

[0016] The beneficial effects of the present invention are as follows: the preparation method provided by the present invention casts an aluminum alloy ingot according to the mass percentage of aluminum alloy elements, and then performs homogenization treatment, hot extrusion treatment, superplastic die forging treatment and heat treatment on the aluminum alloy ingot to obtain an aluminum alloy for preparing a train external bogie traction rod. The method 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.

[0017] Furthermore, the specific method for casting the aluminum alloy ingot is as follows: pure Al is melted into an Al melt, the temperature of the Al melt is raised to 670-710°C, and an Al-Cu master alloy is added; after the Al-Cu master alloy is melted, the temperature of the Al melt is raised to 1290-1350°C, and Al-Nb, Al-Si and Al-Ni master alloys are added; after the Al-Nb, Al-Si and Al-Ni master alloys are melted, the temperature of the Al melt is lowered to 730-750°C, and Al-Zr, Al-Ti, Al-Mn and Al-Y master alloys are added; after the master alloy is melted; the temperature of the Al melt is lowered to 670-710°C, pure Zn and pure Mg are added, and then the temperature of the Al melt is raised to 720-740°C, stirred for 2-10 minutes, and then allowed to stand for 5-30 minutes, and when the temperature is lowered to 710-730°C, casting is performed.

[0018] Furthermore, the specific method of homogenization treatment is: remove the outer skin of the aluminum alloy ingot, heat it to 380-455°C and keep it for 8-72h, then continue to heat it to 455-500°C and keep it for 20-72h, and water cool it at 10-35°C.

[0019] Furthermore, the specific method of hot extrusion treatment is: heating the aluminum alloy ingot after homogenization treatment to 370-450°C and keeping it warm for 2-10 hours, and then hot extruding, the extrusion temperature is 380-460°C, and the extrusion ratio is 9-30:1.

[0020] Furthermore, the specific method of superplastic die forging is: heating the extruded billet to 380-470°C for 2-12 hours, and then placing the extruded billet in a pre-forging die for forging to obtain a pre-forging billet, the forging temperature is 380-470°C, the die forging rate is 10 -5 ~10 -1 mm / s.

[0021] Furthermore, the specific method of superplastic die forging final forging is: placing the pre-forged blank in the final forging die for forging to obtain a rough product, the forging temperature is 380-470°C, the die forging rate is 10 -5 ~10 -1 mm / s.

[0022] The beneficial effects of the present invention are as follows: the aluminum alloy manufactured by the superplastic die forging method has low rheological resistance, good alloy fluidity, uniform plastic deformation, and small and uniform grain size, which is helpful to improve and enhance the mechanical properties of the aluminum alloy, especially has good fatigue performance. The design of two-step superplastic die forging avoids the formation of defects of the aluminum alloy during the die forging process, reduces the stress concentration of the train external bogie traction rod made of the aluminum alloy, and effectively ensures the safety and reliability of the train external bogie traction rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the geometric structure diagram of the traction rod of the train's external bogie;

[0024] Figure 2 This is a sample picture of the train's external bogie traction rod. DETAILED DESCRIPTION

[0025] The specific implementation modes of the present invention are described in detail below with reference to the embodiments.

[0026] Example 1

[0027] An aluminum alloy for preparing a traction rod of an external bogie of a train, wherein the mass percentages of chemical elements are: 7.0% Zn, 2.4% Mg, 2.8% Cu, 0.28% Zr, 0.19% Ti, 0.18% Mn, 0.18% Y, 2.9% Ni, 5.0% Si and 0.06% Nb, and the rest is Al.

[0028] The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie comprises the following steps:

[0029] S1: According to the mass percentage of the elements of the aluminum alloy, pure Al is placed in a crucible, heated to 660°C to melt the pure Al into an Al melt, the temperature of the Al melt is raised to 700°C, and an Al-Cu master alloy is added; after the Al-Cu master alloy is melted, the temperature of the Al melt is raised to 1300°C, and Al-Nb, Al-Si and Al-Ni master alloys are added; after the Al-Nb, Al-Si and Al-Ni master alloys are melted, the temperature of the Al melt is lowered to 740°C, and Al-Zr, Al-Ti, Al-Mn and Al-Y master alloys are added; after the master alloy is melted; the temperature of the Al melt is lowered to 690°C, pure Zn and pure Mg are added, and then the Al melt is heated to 730°C, stirred for 8 minutes, and then allowed to stand for 20 minutes. When the temperature drops to 720°C, casting is performed to obtain an aluminum alloy ingot;

[0030] S2: removing the outer skin of the aluminum alloy ingot, heating it to 420°C and keeping it for 36 hours, then continuing to heat it to 480°C and keeping it for 48 hours, and then cooling it with water at 25°C to obtain the aluminum alloy ingot after homogenization treatment;

[0031] S3: heating the aluminum alloy ingot after homogenization treatment to 400° C. and keeping the temperature for 6 hours, and then extruding at 420° C. and an extrusion ratio of 15:1 to obtain an extruded ingot;

[0032] S4: Heat the extruded billet to 430℃ and keep it for 6h, then place the extruded billet in a pre-forging die and heat it at 430℃ for 10 -3 Forging is carried out under the condition of die forging rate of mm / s to obtain pre-forged blank;

[0033] S5: Place the pre-forged billet in the final forging die and heat at 430℃ for 10 -3 Forging is carried out under the condition of die forging rate of mm / s to obtain a crude product;

[0034] S6: The crude product is heated to 470° C. and kept at this temperature for 6 hours, water-cooled at room temperature, and then heated to 130° C. and kept at this temperature for 15 hours. After air-cooling, an aluminum alloy for preparing a traction rod of an external bogie of a train is obtained.

[0035] Example 2

[0036] An aluminum alloy for preparing a traction rod of an external bogie of a train, wherein the mass percentages of chemical elements are: 5.8% Zn, 3.2% Mg, 1.3% Cu, 0.35% Zr, 0.08% Ti, 0.2% Mn, 0.05% Y, 2.2% Ni, 4.5% Si and 0.02% Nb, and the rest is Al.

[0037] The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie comprises the following steps:

[0038] S1: According to the mass percentage of the elements of the aluminum alloy, pure Al is placed in a crucible, heated to 660°C to melt the pure Al into an Al melt, the temperature of the Al melt is raised to 670°C, and an Al-Cu master alloy is added; after the Al-Cu master alloy is melted, the temperature of the Al melt is raised to 1290°C, and Al-Nb, Al-Si and Al-Ni master alloys are added; after the Al-Nb, Al-Si and Al-Ni master alloys are melted, the temperature of the Al melt is lowered to 730°C, and Al-Zr, Al-Ti, Al-Mn and Al-Y master alloys are added; after the master alloy is melted; the temperature of the Al melt is lowered to 670°C, pure Zn and pure Mg are added, and then the Al melt is heated to 720°C, stirred for 10 minutes, and then allowed to stand for 30 minutes. When the temperature drops to 710°C, casting is performed to obtain an aluminum alloy ingot;

[0039] S2: removing the outer skin of the aluminum alloy ingot, heating it to 370°C and keeping it for 72 hours, then heating it to 455°C and keeping it for 72 hours, and then cooling it with water at 10°C to obtain the aluminum alloy ingot after homogenization treatment;

[0040] S3: heating the aluminum alloy ingot after homogenization treatment to 370° C. and keeping the temperature for 10 hours, and then extruding the ingot at 380° C. and an extrusion ratio of 9:1 to obtain an extruded ingot;

[0041] S4: Heat the extruded billet to 380℃ and keep it for 12h, then place the extruded billet in a pre-forging die and heat it at 380℃ for 10 -5 Forging is carried out under the condition of die forging rate of mm / s to obtain pre-forged blank;

[0042] S5: Place the pre-forged billet in the final forging die and heat at 380℃ for 10 -5 Forging is carried out under the condition of die forging rate of mm / s to obtain a crude product;

[0043] S6: The crude product is heated to 440° C. and kept at this temperature for 10 hours, water-cooled at room temperature, and then heated to 110° C. and kept at this temperature for 26 hours. After air-cooling, an aluminum alloy for preparing a traction rod of an external bogie of a train is obtained.

[0044] Example 3

[0045] An aluminum alloy for preparing a traction rod of an external bogie of a train, wherein the mass percentages of chemical elements are: 8.0% Zn, 1.1% Mg, 3.0% Cu, 0.07% Zr, 0.2% Ti, 0.04% Mn, 0.3% Y, 3.6% Ni, 5.5% Si and 0.1% Nb, and the rest is Al.

[0046] The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie comprises the following steps:

[0047] S1: According to the mass percentage of the elements of the aluminum alloy, pure Al is placed in a crucible, heated to 660°C to melt the pure Al into an Al melt, the temperature of the Al melt is raised to 710°C, and an Al-Cu master alloy is added; after the Al-Cu master alloy is melted, the temperature of the Al melt is raised to 1350°C, and Al-Nb, Al-Si and Al-Ni master alloys are added; after the Al-Nb, Al-Si and Al-Ni master alloys are melted, the temperature of the Al melt is lowered to 750°C, and Al-Zr, Al-Ti, Al-Mn and Al-Y master alloys are added; after the master alloy is melted; the temperature of the Al melt is lowered to 710°C, pure Zn and pure Mg are added, and then the Al melt is heated to 740°C, stirred for 2 minutes, and then allowed to stand for 5 minutes. When the temperature drops to 730°C, casting is performed to obtain an aluminum alloy ingot;

[0048] S2: removing the outer skin of the aluminum alloy ingot, heating it to 450°C and keeping it for 8 hours, then continuing to heat it to 500°C and keeping it for 20 hours, and then water cooling it at 35°C to obtain the aluminum alloy ingot after homogenization treatment;

[0049] S3: heating the aluminum alloy ingot after homogenization treatment to 450° C. and keeping the temperature for 2 h, and then extruding the ingot at 460° C. and an extrusion ratio of 30:1 to obtain an extruded ingot;

[0050] S4: Heat the extruded billet to 470℃ and keep it for 2h, then place the extruded billet in a pre-forging die and heat it at 470℃ for 10 -1 Forging is carried out under the condition of die forging rate of mm / s to obtain pre-forged blank;

[0051] S5: Place the pre-forged billet in the final forging die and heat at 470℃ for 10 -1 Forging is carried out under the condition of die forging rate of mm / s to obtain a crude product;

[0052] S6: The crude product is heated to 500° C. and kept at this temperature for 2 hours, water-cooled at room temperature, and then heated to 150° C. and kept at this temperature for 5 hours. After air-cooling, an aluminum alloy for preparing a traction rod of an external bogie of a train is obtained.

[0053] Comparative Example 1

[0054] An aluminum alloy for preparing a traction rod of an external bogie of a train, wherein the mass percentages of chemical elements are: 7.0% Zn, 2.4% Mg, 2.8% Cu, 0.28% Zr, 0.19% Ti and 0.18% Mn, and the rest is Al.

[0055] The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie comprises the following steps:

[0056] S1: According to the mass percentage of the elements of the aluminum alloy, pure Al is placed in a crucible, heated to 660°C to melt the pure Al into an Al melt, the temperature of the Al melt is raised to 670°C, and an Al-Cu master alloy is added; after the Al-Cu master alloy is melted, the temperature of the Al melt is raised to 730°C, and Al-Zr, Al-Ti and Al-Mn are added; after the master alloy is melted, the temperature of the Al melt is lowered to 710°C, pure Zn and pure Mg are added, and then the Al melt is heated to 730°C, stirred for 8 minutes, and then allowed to stand for 20 minutes. When the temperature drops to 720°C, casting is performed to obtain an aluminum alloy ingot;

[0057] S2: removing the outer skin of the aluminum alloy ingot, heating it to 420°C and keeping it for 36 hours, then continuing to heat it to 480°C and keeping it for 48 hours, and then cooling it with water at 25°C to obtain the aluminum alloy ingot after homogenization treatment;

[0058] S3: heating the aluminum alloy ingot after homogenization treatment to 400° C. and keeping the temperature for 6 hours, and then extruding at 420° C. and an extrusion ratio of 15:1 to obtain an extruded ingot;

[0059] S4: Heat the extruded billet to 430℃ and keep it for 6h, then place the extruded billet in a pre-forging die and heat it at 430℃ for 10 -3 Forging is carried out under the condition of die forging rate of mm / s to obtain pre-forged blank;

[0060] S5: Place the pre-forged billet in the final forging die and heat at 430℃ for 10 -3 Forging is carried out under the condition of die forging rate of mm / s to obtain a crude product;

[0061] S6: The crude product is heated to 470° C. and kept at this temperature for 6 hours, water-cooled at room temperature, and then heated to 130° C. and kept at this temperature for 15 hours. After air-cooling, an aluminum alloy for preparing a traction rod of an external bogie of a train is obtained.

[0062] Comparative Example 2

[0063] An aluminum alloy for preparing a traction rod of an external bogie of a train, wherein the mass percentages of chemical elements are: 7.0% Zn, 2.4% Mg, 2.8% Cu, 0.28% Zr, 0.19% Ti, 0.18% Mn, 0.18% Y, 2.9% Ni, 5.0% Si and 0.06% Nb, and the rest is Al.

[0064] The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie comprises the following steps:

[0065] S1: According to the mass percentage of the elements of the aluminum alloy, pure Al is placed in a crucible, heated to 660°C to melt the pure Al into an Al melt, the temperature of the Al melt is raised to 700°C, and an Al-Cu master alloy is added; after the Al-Cu master alloy is melted, the temperature of the Al melt is raised to 1300°C, and Al-Nb, Al-Si and Al-Ni master alloys are added; after the Al-Nb, Al-Si and Al-Ni master alloys are melted, the temperature of the Al melt is lowered to 740°C, and Al-Zr, Al-Ti, Al-Mn and Al-Y master alloys are added; after the master alloy is melted; the temperature of the Al melt is lowered to 690°C, pure Zn and pure Mg are added, and then the Al melt is heated to 730°C, stirred for 8 minutes, and then allowed to stand for 20 minutes. When the temperature drops to 720°C, casting is performed to obtain an aluminum alloy ingot;

[0066] S2: removing the outer skin of the aluminum alloy ingot, heating it to 420°C and keeping it for 36 hours, then continuing to heat it to 480°C and keeping it for 48 hours, and then cooling it with water at 25°C to obtain the aluminum alloy ingot after homogenization treatment;

[0067] S3: heating the aluminum alloy ingot after homogenization treatment to 400° C. and keeping the temperature for 6 hours, and then extruding at 420° C. and an extrusion ratio of 15:1 to obtain an extruded ingot;

[0068] S4: Heat the extruded billet to 430℃ and keep it for 6h, then place the extruded billet in a pre-forging die and heat it at 430℃ for 10 -6 Forging is carried out under the condition of die forging rate of mm / s to obtain pre-forged blank;

[0069] S5: Place the pre-forged billet in the final forging die and heat at 430℃ for 10 -5 Forging is carried out under the condition of die forging rate of mm / s to obtain a crude product;

[0070] S6: The crude product is heated to 470° C. and kept at this temperature for 6 hours, water-cooled at room temperature, and then heated to 130° C. and kept at this temperature for 15 hours. After air-cooling, an aluminum alloy for preparing a traction rod of an external bogie of a train is obtained.

[0071] Experimental example

[0072] Performance test: The aluminum alloys for preparing the traction rods of the external bogies of trains prepared in Examples 1 to 3, Comparative Example 1 and Comparative Example 2 were Figure 1 The geometry shown is machined to obtain Figure 2 The train external bogie traction rod is then subjected to performance tests, including tensile strength, yield strength, fatigue resistance, etc. The fatigue test parameters are: stress ratio 0.1, vibration frequency 60-70 Hz, and cycle number 1×10 7 The test results are shown in Table 1.

[0073] Table 1 Test results

[0074]

[0075]

[0076] In summary, the strength test results of Examples 1 to 3 are better than those of Comparative Examples 1 to 2, indicating that the aluminum alloy formula and preparation process of the present invention enable the final finished aluminum alloy to have excellent strength properties.

[0077] Although the specific implementation of the present invention is described in detail in conjunction with the embodiments, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. An aluminum alloy for preparing a traction rod of an external bogie of a train, characterized in that: The mass percentages of chemical elements in the aluminum alloy are: 5.8-8.0% Zn, 1.1-3.2% Mg, 1.3-3.0% Cu, 0.07-0.35% Zr, 0.08-0.2% Ti, 0.04-0.2% Mn, 0.05-0.3% Y, 2.2-3.6% Ni, 4.5-5.5% Si and 0.02-0.1% Nb, and the rest is Al.

2. The aluminum alloy for preparing a traction rod for an external bogie of a train according to claim 1, characterized in that: The mass percentages of chemical elements in the aluminum alloy are: 7.0% Zn, 2.4% Mg, 2.8% Cu, 0.28% Zr, 0.19% Ti, 0.18% Mn, 0.18% Y, 2.9% Ni, 5.0% Si and 0.06% Nb, and the rest is Al.

3. The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie according to claim 1 or 2, characterized in that: The following steps are involved: S1: pouring aluminum alloy ingots according to the mass percentage of the elements of the aluminum alloy; S2: homogenizing the aluminum alloy ingot; S3: hot extruding the aluminum alloy ingot after homogenization to obtain an extruded ingot; S4: preheating the extruded billet and then sequentially performing superplastic die forging pre-forging and superplastic die forging final forging to obtain a crude product; S5: The crude product is heated to 440-500° C. and kept at this temperature for 2-10 hours, and then water-cooled at room temperature; then heated to 110-150° C. and kept at this temperature for 9-26 hours, and air-cooled to obtain an aluminum alloy for preparing a traction rod of an external bogie of a train.

4. The method for preparing an aluminum alloy for preparing a traction rod of an external bogie of a train according to claim 3, characterized in that: The specific method for casting the aluminum alloy ingot is as follows: pure Al is melted into Al melt, the temperature of the Al melt is raised to 670-710°C, and an Al-Cu master alloy is added; after the Al-Cu master alloy is melted, the temperature of the Al melt is raised to 1290-1350°C, and Al-Nb, Al-Si and Al-Ni master alloys are added; after the Al-Nb, Al-Si and Al-Ni master alloys are melted, the temperature of the Al melt is lowered to 730-750°C, and Al-Zr, Al-Ti, Al-Mn and Al-Y master alloys are added; after the master alloy is melted, the temperature of the Al melt is lowered to 670-710°C, pure Zn and pure Mg are added, and then the temperature of the Al melt is raised to 720-740°C, stirred for 2-10 minutes, and then allowed to stand for 5-30 minutes, and when the temperature is lowered to 710-730°C, casting is performed.

5. The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie according to claim 3, characterized in that: The specific method of the homogenization treatment is: remove the outer skin of the aluminum alloy ingot, heat it to 380-455°C and keep it for 8-72h, then continue to heat it to 455-500°C and keep it for 20-72h, and water cool it at 10-35°C.

6. The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie according to claim 3, characterized in that: The specific method of the hot extrusion treatment is: heating the aluminum alloy ingot after homogenization treatment to 370-450° C. and keeping it warm for 2-10 hours, and then performing hot extrusion, the extrusion temperature is 380-460° C., and the extrusion ratio is 9-30:

1.

7. The method for preparing an aluminum alloy for preparing a traction rod of an external bogie of a train according to claim 3, characterized in that: The specific method of the superplastic die forging pre-forging is: heating the extruded billet to 380-470°C and keeping the temperature for 2-12 hours, then placing the extruded billet in a pre-forging die for forging to obtain the pre-forging billet, the forging temperature is 380-470°C, the die forging rate is 10 -5 ~10 -1 mm / s.

8. The method for preparing the aluminum alloy for preparing the traction rod of the train external bogie according to claim 7, characterized in that: The specific method of the superplastic die forging final forging is: placing the pre-forged blank in the final forging die for forging to obtain a rough product, the forging temperature is 380-470°C, the die forging rate is 10 -5 ~10 -1 mm / s.

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