Effect of Heat Treatment Process on the Microstructure and Properties of A356 Alloy after Modification

Author of the article:YUAN Changwen 1 , LI Jing 1 , WANG Qihang 1 , SU Xiaojie 2 , HUANG Zhongyue 1

Author's Workplace：1. School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China; 2. Hefei Qiming New Material Technology Development Co., Ltd., Hefei 230031, China

Key Words：A356 alloy; microstructure; mechanical properties; solution treatment; aging treatment

Abstract：The mechanical properties of modified A356 alloys often fail to meet the requirements of industrial use, and need to be further strengthened by heat treatment. In this paper, the effect of solution and aging treatment on the microstructure and mechanical properties of A356 alloy modified by Al-Sr-Y alloy was studied by applying OM, SEM and tensile testing machine, so as to explore a heat treatment process applicable to the modified A356 alloy. The results show that the eutectic silicon after the heat treatment of 540 ℃×4 h+175 ℃×6 h is more rounded and uniform, and the strengthened element Mg in the alloy can be fully dissolved into the matrix, which is conducive to the precipitation of the strengthened phase during aging treatment. The tensile strength, yield strength, and elongation of the alloy after heat treatment are 303.5, 223.1 MPa and 9.5%, respectively, which are 57.7%, 99.7% and 20.3% higher than those of the as-cast modification alloy. The size of dimples in fracture increases, and the plasticity increases since it changes from brittle to ductile fracture.