Effect of initial microstructure on the dynamic recrystallization behavior of Mg-Gd-Y-Zr alloy

The microstructural evolutions during hot deformation of Mg-8Gd-3Y-0.4Zr (wt%, GW83K) alloy with various initial microstructures are investigated by means of isothermal hot compression tests at 400 degrees C with strain rates of 0.005, 0.05 and 0.5 s(-1). The critical strain for initiation of dynamic recrystallization (DRX) for the extruded material is considerably lower than for the as-cast material. The volume fraction of DRX grains increases with strain in a sigmoidal form and the rate with which the percentage DRX increases for the as-cast material is considerably lower than for the extruded material. In addition, the average DRX grain size of hot deformed GW83K alloy is reduced by increasing the strain rate and is independent of the initial microstructure and strain. Continuous DRX is the dominant mechanism as deformation proceeds. The grain boundary bulging is suppressed via solute segregation at grain boundaries, and continuous DRX is promoted by nonbasal slip, which is responsible for the texture weakening phenomenon in GW83K alloy. (c) 2012 Elsevier B.V. All rights reserved.