Enhancing plastic deformability of Mg and its alloys—A review of traditional and nascent developments

Mg and its alloys have continued to attract interest for several structural and super-sensitive applications because of their light weight and good combination of engineering properties. However for some of these applications, high plastic deformability is required to achieve desired component shapes and configurations; unfortunately, Mg and its alloys have low formability. Scientifically, the plastic behaviour of Mg and its alloys ranks among the most complex and difficult to reconcile in metallic material systems. But basically, the HCP crystal structure coupled with low stacking fault energies (SFE) are largely linked to the poor ductility exhibited by Mg alloys. These innate material characteristics have regrettably limited wide spread applicability of Mg and its alloys. Several research efforts aimed at exploring processing strategies to make these alloys more amenable for high formability – mediated engineering use have been reported and still ongoing. This paper reviews the structural metallurgy of Mg alloys and its influence on mechanical behaviour, specifically, plasticity characteristics. It also concisely presents various processing routes (Alloying, Traditional Forming and Severe Plastic Deformation (SPD)) which have been explored to enhance plastic deformability in Mg and its alloys. Grain refinement and homogenising of phases, reducing CRSS between slip modes, twinning suppression to activate non-basal slip, and weakening and randomisation of the basal texture were observed as the formability enhancing strategies explored in the reviewed processes. While identifying the limitations of these strategies, further areas to be explored for enhancing plasticity of Mg alloys are highlighted. Keywords: Mg alloys, HCP crystal structure, Basal texture, Severe plastic deformation, Formability