Microstructure Heredity and High Yield Strength Design of Fine Grained Al-Si-Mg Alloys
LI Daoxiu1, HAN Mengxia1, ZHANG Jiang2, PENG Yinjiang2, SUN Qianqian1,3, LIU Guiliang1,3, LIU Xiangfa1,*
1 Key Laboratory for Liquid-Solid Structural Evolution & Processing of Materials of Ministry of Education, Shandong University, Jinan 250061, China 2 Ningbo Branch of Chinese Academy of Ordnance Science, Ningbo 315103, China 3 Shandong Al & Mg Melt Tech. Co., Ltd., Jinan 250061, China
Abstract: The grain size of conventional Al-Si-Mg alloy ingot (such as A356 cast ingot) is abnormally coarse, which leads to the casting defects of microstructure shrinkage and porosity, uneven structure composition and poor performance after remelting. Therefore, it is very important to control its grain size effectively. In this work, a fine grained A356 alloy was remelted and its microstructure heredity was studied. The Al-Si-Mg alloy with high strength was designed by using the fine grain A356 aluminum alloy. To reveal the correlative heredity mechanism, the nucleation particle of the fine grained A356 aluminum alloy was characterized by electron microprobe (EPMA), and the solidification process was analyzed by differential scanning calorimetry (DSC). The results showed that the average grain size of the fine grained A356 aluminum alloy was 74.9 μm after remelting. It is found that the α-Al grains of the fine grained A356 aluminum alloy contains ternary compound TiCB particles (TCB). The particles are stable in the remelted A356 aluminum alloy, which are able to reduce the supercooling degree of the alloy. Therefore, even if remelted for a long time, it is qualified for α-Al nucleating and retain the high-efficiency refining effect. In addition, the tensile strength of the fine grain A356 aluminum alloy after remelting is 312.5 MPa, and the elongation reaches 12.5%. On this basis, a small amount of Mg was added to improve the strength. The designed Al-Si-Mg alloy has excellent mechanical property. The tensile strength and yield strength of Al-7Si-0.8Mg alloy are 386.4 MPa and 352.9 MPa, respectively, while the elongation remains at 3.9%.
李道秀, 韩梦霞, 张将, 彭银江, 孙谦谦, 刘桂亮, 刘相法. 细晶Al-Si-Mg合金的组织遗传性与高屈服强度设计[J]. 材料导报, 2021, 35(9): 9003-9008.
LI Daoxiu, HAN Mengxia, ZHANG Jiang, PENG Yinjiang, SUN Qianqian, LIU Guiliang, LIU Xiangfa. Microstructure Heredity and High Yield Strength Design of Fine Grained Al-Si-Mg Alloys. Materials Reports, 2021, 35(9): 9003-9008.
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