Effect of Mg on dynamic recrystallization of Zn–Mg alloys during room-temperature compression

Abstract

This work reveals the role of Mg additions on deformation behaviours of Zn–Mg alloys during room temperature compression at moderately high strain rate of ∼0.5 s-1. Experimental results from scanning electron microscopy, transmission electron microscopy and electron backscatter diffraction provide insight into the deformation behaviours and dynamic recrystallization mechanisms operative in Zn-0.08%Mg and Zn-0.8%Mg alloys. The primary dynamic recrystallization mechanisms in the Zn-0.08%Mg alloy were continuous dynamic recrystallization in conjunction with twin-induced dynamic recrystallization. After straining to a true strain of 161%, the Zn-0.08%Mg alloy displayed a uniform and heavily refined microstructure with an excellent combination of strength and plasticity. For the Zn-0.8%Mg alloy, particle-induced dynamic recrystallization activated by eutectic structures played a critical role in addition to continuous and twin-induced dynamic recrystallization mechanisms. Fine and soft-oriented grains which formed in proximity to the eutectic accommodated large amounts of localized plastic strain. This resulted in inhomogeneous strain partitioning which restricted dynamic recrystallization kinetics in hard-oriented grain interior regions due to insufficient slip activity to support continuous dynamic recrystallization. Therefore, a partially recrystallized microstructure was maintained in the Zn-0.8%Mg alloy up to true strain of 161%.