Microstructure of AZ91D in Different Treatment Conditions

The microstructures of magnesium alloy AZ91D in as-cast, solid solution and aging conditions were studied by optical, scanning electron and transmission electronic microscopes. The relationship between microstructure and the microhardness was analyzed. It has been found that the microhardness in the matrix varied slightly with the increasing solution time, but increased quickly with the aging time. The difference of the microhardness between the matrix and the second phase in as-cast condition is larger than that in T6 aging condition, because the aluminum-zinc-magnesium (poor) phase existed in the as-cast condition.