Effects Of Alloy Elements And Heat Treatment Process On The Microstructure And Mechanical Properties Of Al-Mg-Si-Cu Alloy

Al-Mg-Si-Cu alloy has high specific strength, perfect corrosion resistance, good plasticity, easy processing and other advantages, thus becoming the main materials of lightweight automobile body and high speed trains aluminum alloy body instead of some iron and steel materials gradually. Along with the rapid development of aerospace and transportation industries, improvement in mechanical properties of aluminum alloy has become more and more essential. While the strength and plasticity of traditional Al-Mg-Si-Cu alloy are yet to be improved. Al-Mg-Si-Cu alloy is widely used in the field of forging, but the forging temperature is very narrow, so it is very easy to produce overheating and coarse grain phenomena, thus resulting in poor forging performance. Aiming at the above problems, the Al-Mg-Si-Cu alloy was taken as the research object in this paper, the heat treatment process and micro-alloying effect of alloy elements were investigated. The research contents can be concluded as follows:(1) The composition of alloy was designed by consulting 6061 aluminum alloy, the content of Cu was increased, and the Al-Mg-Si-Cu alloy was produced by ingot-metallurgy method. The homogenization processing, rolling deformation, solid solution and aging treatment of alloy ingot were conducted.(2) The forging temperature of Al-Mg-Si-Cu alloy is very narrow, so the method of combining scandium microalloying and solid solution and aging reinforcement was explored to improve the comprehensive performance of Al-Mg-Si-Cu alloy.(3) Aiming at the high price of scandium, scanduim is replaced by erbium, the effect of minor content of erbium and solid solution and aging reinforcement on the microstructure and mechanical properties of Al-Mg-Si-Cu alloy was investigated.The results show that the mechanical properties of Al-Mg-Si-Cu alloy are improved by adding 0.3wt% scandium and solid solution and aging reinforcement, the tensile strength, yield strength and elongation rate reach 389MPa,351MPa and 25.2%, respectively. What’s more, the forging temperature interval of the alloy is increased by 50 ℃. Whereas the tensile strength, yield strength and elongation rate of Al-Mg-Si-Cu alloy reach 388MPa,350MPa and 22.7%, respectively, by adding 0.3wt% erbium and solid solution and aging reinforcement, and the forging temperature interval of the alloy is increased by 40 ℃. In a word, the micro-alloying effect of erbium is less obvious than scandium. Taking both the production cost and the little bad influence on mechanical properties into consideration, it is preferable to select Al-Mg-Si-Cu-0.3Er alloy as a new material of high performance aluminum alloy.