Recrystallization of preformed AZ91D magnesium alloys in the semisolid state

The microstructural evolutions preformed AZ91D magnesium alloys were examined by the isothermal soaking and rapid quenching in semisolid state. Quenching specimens reveal that the microstructures of preformed AZ91D alloys changed from deformed textures to near-equiaxed grains and then to polygonal particulates, and finally to spherical grains. Recovery and recrystallization of preformed alloys in semisolid state resulted in the microstructure evolution. Local melting, which was caused by the higher free energy composed of residual stress, fault energy and thermal activation energy, improved the recrystallization. Rising the soaking temperature, recrystallization is accelerated. The relationship between grain size and soaking time can be expressed as R=Ctη. Five types of interface in the recrystallization are discussed in this paper.