Study on Microstructure and Property of Al-Si-Cu-Mg Casting Alloy during Solution and Aging Treatment

Abstract

The effect of the alloying elements Cu and Mg, the solution and artificial aging process on the microstructure and property were investigated. Solution treatment was carried out at 535 ± 5°C in different time for the Al-Si-Cu-Mg casting alloy, and the artificial aging was carried out at 160 ± 5°C and 175 ± 5°C and190 ± 5°C in different time. The microstructure has been investigated by Optical Microscopy, Scanning Electron Microscopy (SEM). We found that most of Cu and Mg element in the alloy gathered and formed multivariate composite phase at grain boundaries. With the increasing of solid solution time, the intermetallic phases will be dissolution into the matrix, and if the solid solution time is long enough, they will be distributed uniformly in alloy. With the increase of the aging temperature, the time for aging peak will be shorter, but the peak will be lower. Finally, we determine the optimum heat treatment process is 535°C × 12h + 175°C × 8h。