Mechanical Properties and Microstructural Evolution of Rheo-diecast AZ91D Magnesium Alloy During Heat Treatment

摘要

Mechanical properties and micro structural evolution of rheodiecast (RDC) AZ91D alloy during heat treatment (HT) have been studied. The semi-solid processed alloy exhibits a unique solidification micro structure featuring the uniformly distributed primary α-Mg globules, the fine secondary α-Mg grains and the β-Mg17Al12 network. Compared with high-pressure die-cast AZ91D alloy, the RDC alloy displays a faster solution response and accelerated precipitation during HT. A new HT schedule Tx, has been developed, which was carried out at a temperature close to the solvus to break up the β-phase network. HT offers improvement to mechanical properties and the Tx treatment gives a superior combination of strength and ductility. The accelerated HT kinetics for the RDC alloy and the lower temperature and shorter time of the Tx indicate a considerable reduction in HT cost.