China Foundry (Nov 2008)
Microstructural evolution of equal channel angular pressed AZ91D magnesium alloy during semi-solid isothermal heat treatment
Abstract
The microstructural evolution of AZ91D magnesium alloy processed by equal channel angular pressing during isothermal heat treatment at 570℃ was investigated. The results indicated that the equal channel angular pressing followed by semi-solid isothermal heat treatment was an effective method to prepare semisolid nondendritic slurry of AZ91D magnesium alloy. During this process, its microstructure change underwent four stages, the initial coarsening stage, the structure separation stage, the spheroidization stage and the final coarsening stage. The microstructural spheroidization effect was the best after being heated for 15 min for the alloy pressed for four passes, and the grain size was the smallest. With the further increase of heating time, the grain size and shape factor increased. When the heating time was kept constant, the grain size and shape factor decreased with the increase of pressing passes.
