Aluminum alloy for new energy vehicle integral die-cast part, preparation method therefor and application thereof

Abstract

Disclosed is an aluminum alloy for a new energy vehicle integral die-cast part, a preparation method therefor and an application thereof. The alloy includes 7-9 wt % of Si, 0.05-0.25 wt % of Mg, Cu<0.5 wt %, Zn<0.5 wt %, 0.001-0.20 wt % of B, 0.05-0.2 wt % of Ti, 0.1-0.9 wt % of Mn, 0.05-0.3 wt % of Fe, 0.005-0.5 wt % of Sr, Ce<0.5 wt %, 0.01-0.1 wt % of Zr, 0.001-0.3 wt % of Mo, a sum of weight percentages of remaining impurities being controlled to be 1.0 wt % or less, and the balance being Al. Compared with the prior art, the alloy significantly improves an elongation of a material and effectively improves a strength of the material, such that the material has a tensile strength of 260-300 MPa, a yield strength of 110-130 MPa and an elongation of 10-14%.

Claims

1. A method for preparing an aluminum alloy for a new energy vehicle integral die-cast part, wherein the alloy comprises 7-9 wt % of Si, 0.05-0.25 wt % of Mg, Cu<0.5 wt %, Zn<0.5 wt %, 0.001-0.20 wt % of B, 0.05-0.2 wt % of Ti, 0.1-0.9 wt % of Mn, 0.05-0.3 wt % of Fe, 0.005-0.5 wt % of Sr, Ce<0.5 wt %, 0.01-0.1 wt % of Zr, 0.001-0.3 wt % of Mo, a sum of weight percentages of remaining impurities being controlled to be 1.0 wt % or less, and the balance being Al; wherein the method comprises following steps: putting aluminum element into a heating furnace, heating the aluminum element to a temperature of 680° C., and maintaining the temperature for 15 min after melting completely; raising the temperature to 760° C., and adding Si, Zn and Cu elements; lowering the temperature to 730° C., and adding Al—Zr, Al—Mn, Al—Mo and Al—Ti—B—Ce amorphous intermediate alloys; wherein the amorphous intermediate alloys are obtained by a way of following method: placing Al—Zr, Al—Mn, Al—Mo and Al—Ti—B—Ce intermediate alloys as target materials in a closed chamber, evacuating the chamber to a vacuum and introducing argon gas of 100-150 kPa, irradiating four target materials respectively with a pulsed laser beam, and finally collecting mixed amorphous powders of Al—Zr, Al—Mn, Al—Mo and Al—Ti—B—Ce with set compositional ratio; wherein a vacuum degree of the chamber is 10.sup.−5 Pa, and a laser energy density of the pulsed laser beam is more than 100 kW/cm.sup.2; lowering the temperature to 710° C., and adding pure Mg metal material; and performing casting to obtain an aluminum alloy ingot after all raw materials are melted.

2. The method according to claim 1, wherein the alloy comprises 0.11-0.35 wt % of Ce.

3. The method according to claim 1, wherein the alloy comprises 7.51 wt % of Si, 0.15 wt % of Mg, 0.23 wt % of Cu, 0.15 wt % of Zn, 0.051 wt % of Ti, 0.53 wt % of Mn, 0.05 wt % of Fe, 0.015 wt % of Sr, 0.11 wt % of Ce, 0.051 wt % of Zr, 0.02 wt % of Mo, 0.06 wt % of B.

4. The method according to claim 1, wherein the alloy comprises 7.53 wt % of Si, 0.15 wt % of Mg, 0.25 wt % of Cu, 0.17 wt % of Zn, 0.049 wt % of Ti, 0.51 wt % of Mn, 0.15 wt % of Fe, 0.018 wt % of Sr, 0.17 wt % of Ce, 0.049 wt % of Zr, 0.27 wt % of Mo, 0.07 wt % of B.

5. The method according to claim 1, wherein the alloy comprises 8.24 wt % of Si, 0.21 wt % of Mg, 0.32 wt % of Cu, 0.21 wt % of Zn, 0.082 wt % of Ti, 0.62 wt % of Mn, 0.21 wt % of Fe, 0.021 wt % of Sr, 0.21 wt % of Ce, 0.057 wt % of Zr, 0.13 wt % of Mo, 0.11 wt % of B.

6. The method according to claim 1, wherein the alloy comprises 8.31 wt % of Si, 0.20 wt % of Mg, 0.35 wt % of Cu, 0.23 wt % of Zn, 0.091 wt % of Ti, 0.71 wt % of Mn, 0.25 wt % of Fe, 0.023 wt % of Sr, 0.23 wt % of Ce, 0.063 wt % of Zr, 0.26 wt % of Mo, 0.13 wt % of B.

7. The method according to claim 1, wherein the alloy comprises 8.56 wt % of Si, 0.23 wt % of Mg, 0.41 wt % of Cu, 0.31 wt % of Zn, 0.134 wt % of Ti, 0.67 wt % of Mn, 0.27 wt % of Fe, 0.025 wt % of Sr, 0.31 wt % of Ce, 0.072 wt % of Zr, 0.11 wt % of Mo, 0.15 wt % of B.

8. The method according to claim 1, wherein the alloy comprises 8.71 wt % of Si, 0.25 wt % of Mg, 0.42 wt % of Cu, 0.33 wt % of Zn, 0.147 wt % of Ti, 0.73 wt % of Mn, 0.30 wt % of Fe, 0.031 wt % of Sr, 0.35 wt % of Ce, 0.085 wt % of Zr, 0.29 wt % of Mo, 0.14 wt % of B.

9. The method according to claim 1, wherein the alloy has a tensile strength of 260-300 MPa, a yield strength of 110-130 MPa and an elongation of 10-14%.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

(1) The following is a detailed description of the examples of the present invention. The examples are implemented on the premise of the technical solution of the present invention, and the detailed implementation method and specific operation process are given. However, the scope of protection of the present invention is not limited to the following examples.

Examples 1-6

(2) An aluminum alloy for a new energy vehicle integral die-cast part comprised the following components in percentage as shown in Table 1, with the balance being aluminum and inevitable impurities.

(3) The alloy material comprised 7-9 wt % of Si, 0.05-0.25 wt % of Mg, Cu<0.5 wt %, Zn<0.5 wt %, 0.001-0.20 wt % of B, 0.05-0.2 wt % of Ti, 0.1-0.9 wt % of Mn, 0.05-0.3 wt % of Fe, 0.005-0.5 wt % of Sr, Ce<0.5 wt %, 0.01-0.1 wt % of Zr, 0.001-0.3 wt % of Mo, a sum of weight percentages of remaining impurities being controlled to be 1.0 wt % or less, and the balance being Al.

(4) Table 1 Table of the contents of the elements in the aluminum alloys of Examples 1-6 and the compositions of the materials prepared therefrom

(5) TABLE-US-00001 TABLE 1 Table of the contents of the elements in the aluminum alloys of Examples 1-6 and the compositions of the materials prepared therefrom Example Si Mg Cu Zn Ti Mn Fe Sr Ce Zr Mo B 1 7.51 0.15 0.23 0.15 0.051 0.53 0.05 0.015 0.11 0.051 0.02 0.06 2 7.53 0.15 0.25 0.17 0.049 0.51 0.15 0.018 0.17 0.049 0.27 0.07 3 8.24 0.21 0.32 0.21 0.082 0.62 0.21 0.021 0.21 0.057 0.13 0.11 4 8.31 0.20 0.35 0.23 0.091 0.71 0.25 0.023 0.23 0.063 0.26 0.13 5 8.56 0.23 0.41 0.31 0.134 0.67 0.27 0.025 0.31 0.072 0.11 0.15 6 8.71 0.25 0.42 0.33 0.147 0.73 0.30 0.031 0.35 0.085 0.29 0.14 1) Materials were prepared according to Table 1 above, wherein Al—Zr, Al—Mn, Al—Mo and Al—Ti—B—Ce intermediate alloys as target materials were placed in a closed chamber, the chamber was evacuated to such a vacuum that the pressure was reduced to 10.sup.−5 Pa, argon gas at 120 kPa was introduced, the four target materials were respectively irradiated with a pulsed laser beam at a density of more than 100 kW/cm.sup.2, and finally, the materials were collected to obtain mixed amorphous powders of Al—Zr, Al—Mn, Al—Mo and Al—Ti—B—Ce at a specific compositional ratio. In this intermediate alloy amorphous powder, the elements Zr, Mn, Mo, Ti and Ce were uniformly dispersed, and the average particle size was 20-50 nm. During smelting, Zr, Mn, Mo, Ti and Ce could be uniformly dispersed in the molten aluminum at a lower capacity temperature; 2) high-purity aluminum element was put into a heating furnace and heated to a temperature of 680° C., and after melting completely, the temperature was maintained for 15 min; 3) the temperature was raised to 760° C., and elemental Si, Zn, and Cu elements were added; 4) the temperature was reduced to 730° C., and mixed amorphous powders of Al—Zr, Al—Mn, Al—Mo and Al—Ti—B—Ce were added; 5) the temperature was reduced to 710° C., and a pure Mg metal material was added; and 6) after all the raw materials were melted, casting was performed to obtain an aluminum alloy ingot.

(6) The aluminum alloy ingot obtained in step 6) was re-melted at a temperature of 750° C., the temperature was maintained, a protective gas was introduced for isolation from the air during the maintaining of the temperature, the molten aluminum alloy was then injected into the die casting mold, and after die pressing, a 3 mm thick tensile sheet specimen was obtained.

(7) The die casting mold was a mold temperature controller, and the temperature thereof was maintained at 250-350° C. in advance. In addition, the die casting machine was equipped with a heat-insulating barrel. During die casting, the barrel temperature was maintained at 200-250° C., an injection speed of 4 m/s was used, and the molten aluminum alloy ingot was rapidly cooled and molded under a pressure of 20-40 MPa. The tensile sheet specimen had a tensile strength of 260-300 MPa, a yield strength of 110-130 MPa and an elongation of 10-14%.

(8) Table 2 Table of the mechanical properties of tensile sheets corresponding to Examples 1-6

(9) TABLE-US-00002 TABLE 2 Table of the mechanical properties of tensile sheets corresponding to Examples 1-6 Mechanical properties Tensile strength Yield strength Elongation Example (MPa) (MPa) (%) 1 271 118 14.00 2 276 120 13.78 3 282 123 12.81 4 287 125 12.67 5 291 127 11.57 6 294 129 11.42

(10) The aluminum alloy ingot obtained by the above method was made into a product of new energy vehicle lower body. Taking the aluminum alloy ingot made in each example as an example, integral die casting molding was performed to make a new energy vehicle lower body. The method therefor comprised the following steps: 21) re-melting the aluminum alloy ingot at a temperature of 750° C., maintaining the temperature, and introducing a protective gas for isolation from the air during the maintaining of the temperature; 22) using 6600T die casting machine, wherein before die casting, a plurality of evacuation valves were arranged at a distal end of the die casting mold, and by adjusting the gas flow rates of different valves for evacuation, the pressure at each valve port was less than 30 mBar, thereby realizing a directional gas flow from proximal end to distal end of the sprue to form a stable pressure differential; 23) pre-filling a barrel with molten alloy obtained in step 21) by means of a punch of the die casting machine, and then injecting the molten alloy into the mold, wherein the punch was a beryllium bronze vacuum sealing punch, an outer diameter of the punch was in transition fit with an inner hole of the barrel to ensure the sealing of the barrel, and the punch was externally provided with an atomized spray lubricant and had a built-in annular groove lubricating device, ensuring that the punch was fully lubricated; 24) using a mold temperature control system, which was an oil-type mold temperature controller, wherein a temperature of the mold was set to 400° C., the diameter of the punch was increased to 300 mm, the low speed of the injection was controlled to be 0.2 m/s, the speed of the pre-filling of the barrel was controlled to be 0.45 m/s, and the speed was increased to 8 m/s at high-speed filling stage, such that the filling of the cavity of the die casting mold could be completed within 200 ms per 90 kg of the molten alloy, whereby a filling distance of 2 m or more was met; a mold retention time of the die-cast part was 45 s; in addition, a high-pressure targeted cooling device was used at a rear wall part to shorten solidification time of a product; and in this example, the mold was a forward engine room mold; 25) spraying a condensed primary product by means of a profiling sprayer to obtain an integral forward engine room die-cast part, wherein the profiling sprayer was used for spraying, the profiling sprayer had a spray nozzle imitating a structure of the product and performed targeted spraying according to a position of the product, which could realize variable spraying methods at different spraying positions and improve spraying efficiency; and 26) after demolding the integral forward engine room die-cast part, taking out the cast part by means of a mechanical arm, placing the cast part in a 20° C. constant temperature water bath for cooling for 30 s, taking out the cast part, and leaving the cast part to stand for 72 h to obtain a new energy vehicle forward engine room product.

(11) The performance of the obtained forward engine room product was tested, and the testing process and results were as follows: taking Examples 3 and 6 as examples, the mechanical properties of the new energy vehicle forward engine room products made according to the above method from the prepared aluminum alloy ingots at different positions proximal end and distal end of the sprue were as shown in Tables 3 and 4 below, wherein the numbers 1 #, 2 #, 3 #, 4 #, 5 # and 6 # were respectively numbers by which the mechanical properties of the new energy vehicle forward engine room products were tested at different positions from the inlet sprue as test points.

(12) Table 3 Mechanical properties of the new energy vehicle forward engine room product made according to the above method from the aluminum alloy ingot made in Example 3 in different positions

(13) TABLE-US-00003 TABLE 3 Mechanical properties of the new energy vehicle forward engine room product made according to the above method from the aluminum alloy ingot made in Example 3 in differnt positions Distance to inlet sprue Tensile strength Yield strength Elongation No. (mm) (MPa) (MPa) (%) 1# 150 287 122 12.81% 2# 470 276 120 12.37% 3# 690 273 119 11.98% 4# 940 267 117 11.32% 5# 1500 265 115 11.21% 6# 2300 263 113 10.54%

(14) Table 4 Mechanical properties of the new energy vehicle forward engine room product made according to the above method from the aluminum alloy ingot made in Example 6 in different positions

(15) TABLE-US-00004 TABLE 4 Mechanical properties of the new energy vehicle forward engine room product made according to the above method from the aluminum alloy ingot made in Example 6 in different positions Distance to inlet sprue Tensile strength Yield strength Elongation No. (mm) (MPa) (MPa) (%) 1# 150 297 128 11.37% 2# 470 286 126 11.14% 3# 690 283 123 10.98% 4# 940 277 121 10.62% 5# 1500 275 118 10.21% 6# 2300 263 116 10.14%

(16) It could be seen from the above tables 3 and 4 that although the content of iron in the alloy of the present invention was relatively high, up to 0.3 wt % (the content of Fe in general automobile die casting alloy needed to be controlled within 0.15 wt %), the mechanical properties of the obtained alloy could still reach a tensile strength of 260-300 MPa, a yield strength of 110-130 MPa, an elongation of 10-14%, and the tolerance to the element Fe was improved. The new energy vehicle forward engine room products made of this alloy had, at different positions, a tensile strength of 260-300 MPa, a yield strength of 110-130 MPa and an elongation of 10-14%; moreover, the strengthening and toughening of the aluminum alloy as effective as in a heat treatment could be achieved, even without a specialized solid solution aging treatment; in addition, at the farthest distance distal to the inlet sprue, i.e. 2300 mm, the tensile strength was 260-300 MPa, the yield strength was 110-130 MPa, and the elongation was 10-14%. The material had excellent casting performance to ensure excellent mold filling capacity.

(17) In the present invention, the tensile strength, yield strength and elongation were detected according to the national standard GB/T 228.1-2010.