Effect of heat treatment on mechanical properties of
thixoformed 7A09 aluminum alloy
(School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
Abstract: The effects of solution-ageing treatment on the mechanical properties of semi-solid metal (SSM) products were studied by the method of orthogonal experiment. The microstructure and tensile properties at different treatment conditions were analyzed. The results show that the effects of solution-ageing treatment were obviously influenced by the original microstructure of the SSM billet. Higher temperature is favorable for the sufficient solution of alloy elements, but the grains will grow up when treated at a higher temperature or soaked for a longer time. There is a contradiction between the maximum tensile strength and elongation percentage. Under the condition of solution treatment at 475 ℃ for 12 h and at 133 ℃ for 20−22 h ageing, better properties including about 540 MPa of tensile strength and more than 6.3% of elongation can be obtained in general. The surplus phases not melted in the substrate and the solution precipitated supersaturated elements are the main factors influencing the properties of the alloys.
Key words: 7A09 aluminum alloy; heat treatment; mechanical property; semi-solid metal (SSM)