Microstructure and tensile properties of squeeze cast AZ91D magnesium alloy

Abstract

Microstructure and tensile properties of squeeze cast AZ91D alloy in different heat treatment conditions are studied. The effect of wall thickness of specimens on tensile properties is also discussed. The results show that the microstructure of squeeze cast AZ91D alloy consists of primary α-Mg matrix and β-Mg17Al12 phase which is mainly present in the matrix and grain boundaries. Single phase α-Mg solid solution is obtained after T4 treatment, and some granular precipitates are present in α-Mg matrix. After T6 treatment, finer β-Mg17Al12 phase precipitates within the α-Mg matrix and along the grain boundaries again. The yield strength (YS) and ultimate tensile strength (UTS) of squeeze cast AZ91D alloy decrease, but the elongation increases with the increase of wall thickness. The SEM analysis of fracture surfaces shows that the squeeze cast AZ91D alloy displays different fracture modes in different heat treatment conditions.