Aluminum alloys are widely used in industry due to their excellent formability, machinability, weldability, and excellent corrosion resistance. In the coming years, the aluminum consumption of electric vehicles will continue to increase, reflected in the body components and battery containers. The battery casing is made of die cast aluminum alloy parts, such as AlSi10MnMg alloy parts. Different researchers have found that aluminum alloy high-pressure die-casting is particularly suitable for the overall forming of integrated parts. Fe is inevitably introduced during the smelting and casting processes, especially when using waste and recycled materials. Fe is a favorable element for improving mechanical properties in Al Mg and Al Mg Mn alloys. Fe significantly increases the yield strength of the alloy, but significantly reduces the elongation. Some studies have also found that an increase in Si content improves the strength of cast alloys, but reduces hardness and plasticity of aluminum alloys. Research has shown that low pressure and low temperature increase porosity, promote the formation of iron rich intermetallic compounds, and alter α- The morphology of Al phase deteriorates the mechanical properties of the alloy. The interaction between die casting process parameters and alloy elements has a significant impact on the tensile properties of alloys.
At present, research on the influence of alloy elements and die-casting process conditions on mechanical properties mainly focuses on short-term production processes. There are few reports on the impact of long-term thermal environment on the mechanical properties of aluminum alloys, considering the unique usage environment of the parts. Therefore, this study compares the mechanical properties of AlSi12 (Fe) (a) alloy and AlSi10MnMg alloy specimens after heat treatment at 500h × 120 ℃, and studies the mechanical stability of thin-walled aluminum alloy high-pressure die castings under long-term thermal environment. This can provide reference for the design and optimization of thin-walled die castings for such new energy vehicles. Select the specimens that have undergone 500h x 120 ℃ pretreatment and ordinary specimens for mechanical performance testing. Although the mechanical properties of AlSi12 (Fe) (a) alloy specimens have changed after pretreatment, they have not decayed below the material standard value. After pre-treatment, the tensile strength and yield strength of AlSi10MnMg alloy specimens were improved, but the elongation decreased and was lower than the standard value of the material.
Graphic and textual results
In the preparation stage, uniform trial production conditions are adopted, and the die-casting process parameters are adjusted according to the actual production conditions. Aluminum alloy liquid melted in the same batch as the die-casting parts is used for die-casting. The non clamped part should have no defects such as scratches, pitting, cold shuts, cracks, inclusions, and surface pores. Both ends should be polished flat, and the feeding port and slag pocket should be removed. The dimension diagram is shown in Figure 1. According to the requirements of the delivery status of the parts, heat treatment is not used. The die casting machine model is UB350iC, the aluminum liquid pouring temperature is (680 ± 10) ℃, the mold temperature machine temperature is (200 ± 10) ℃, the vacuum degree is (40 ± 10) kPa, and the casting pressure is (95 ± 10) MPa. Use FED-720 oven for pretreatment, with pretreatment parameters of 500 h x 120 ℃, and conduct mechanical performance testing. The environmental conditions of the laboratory were set at (23 ± 5) ℃ and (50% ± 25%) (Rh as temperature), and 6 AlSi12 (Fe) (a) alloy specimens and 6 AlSi10MnMg alloy specimens were tested, respectively. Among them, AlSi12 (Fe) (a) alloy specimens 1-3 and AlSi10MnMg alloy specimens 1-3 were not pretreated; The 4th to 6th test bars of two alloys have been pre treated. Use K2012967 digital vernier caliper to measure the diameter of the circular section in the middle of the test bar, and use E45.305 electronic universal testing machine to test the mechanical properties of the test bar.
conclusion
According to the test results in Tables 2 and 3, it can be concluded that the mechanical properties of the material before pretreatment comply with the DIN EN 1706 standard. After pretreatment, although the mechanical properties of AlSi12 (Fe) (a) alloy decreased, it still met the requirements, but the elongation of AlSi10MnMg alloy was lower than the DIN EN 1706 standard.
AlSi12 (Fe) (a) alloy is a eutectic Al Si alloy with high thermal conductivity and good fluidity. It has excellent casting formability and can form complex thin-walled parts, which can meet the production requirements of new energy vehicle battery modules. The heat treatment process of AlSi10MnMg alloy can lead to casting deformation and surface foaming problems, especially as the volume of die castings increases, it is difficult for the parts to undergo secondary shaping. Therefore, on the one hand, the non heat treated die cast aluminum alloy process can be directly used in the as cast state to avoid the above problems. On the other hand, reducing the heat treatment process of parts can also reduce the manufacturing cost of parts.
Batteries generate more heat during high-power operation, therefore, the application of new materials and structural optimization design have become the key to improving the heat dissipation capacity of battery modules in new energy vehicles. Due to its excellent thermal conductivity, processability, low cost, environmental friendliness, and low density, aluminum alloy can achieve miniaturization and lightweighting of new energy vehicle battery modules, while maintaining the high heat dissipation capacity of new energy vehicle battery modules. It is widely used in radiators, load-bearing plates, brackets, junction boxes, front covers, and other new energy vehicle components.
Author of this article:
Zhang Zuowei, Fang Jianru, Zhang Shi'en
Dalian Yaming Automotive Parts Co., Ltd
Zhang Zuowei
Dalian Jiaotong University Continuous Squeezing Engineering Technology Research Center of the Ministry of Education
Source of this article: Journal of Special Casting and Nonferrous Alloys
