Nack Kim

Abstract:

Mg alloys have the lowest density among commercially available structural alloys which can provide significant weight savings in automobiles. For the widespread application of Mg alloys, however, Mg alloys should overcome a critical shortcoming: poor formability at room temperature mainly originating from strong basal texture developed during thermomechanical processing. Although several Mg alloys show random/weak texture and accordingly good room temperature formability, most of such alloys rely on the usage of expensive rare earth elements. It has been recently reported that the addition of Ca to Mg-Zn alloys weakens and randomizes the texture, similar to the effect of RE addition on modification of the texture. The texture of these Ca-containing Mg-Zn alloys can be described as the broadened angular distribution of basal poles along the transverse direction (TD) and split of basal poles along the rolling direction (RD) in as-rolled condition. A significant change in texture, however, occurs after the annealing process, splitting of basal poles toward the TD from the original RD in particular. Despite the weak texture intensity, their texture is less than ideal since one directional orthotropic texture developed during annealing would result in non-uniform deformation during stretch forming. The detailed mechanism of such texture evolution, however, has not been clearly revealed yet. In the present work, an attempt has been made for having a better understanding of the texture evolution during the annealing process of Ca containing Mg-Zn alloys. The details of their texture evolution have been analyzed by quasi-in-situ EBSD after various stages of annealing with particular emphasis on recrystallization and growth behavior.