Enhanced Precipitation and Recrystallization in a Mg-Zn Alloy During Low-Temperature Extrusion

Abstract

Lightweight magnesium (Mg) alloys have great potential to be used in a variety of structural applications. However, Mg’s hexagonal crystal lattice and the limited number of deformation slip systems create fundamental challenges during forming. Furthermore, the selection and amounts of alloying additions can lead to complex phases and transformations or location-sensitive precipitate reactions (i.e., in grain or grain boundary regions). Mg-Zn alloys are promising candidates for applications requiring high strength due to their high hardening response. In this study, we processed solution treated Mg-3Zn (wt.%) using equal channel angular extrusion (ECAE) along the Bc route at 150 oC. The microstructure of the extruded material showed two distinct regions. The grain interior showed a dense distribution of nano precipitates. The grain boundary region contains recrystallized ultrafine grains with some reprecipitation occurring inside them. We employed the Lukác-Balík strain hardening model to estimate the dislocation density evolution during the processing, and we linked these dislocations to the high density of precipitates seen in the grain interiors.