Magnesium alloys are the lightest of all engineering structural alloys and as such have the potential to reduce the weight of structures, particularly in automobiles. The lack of formability of these alloys limits their application particularly for automotive parts formed by drawing and forging. Superplastic deformation offers a change in the mechanism of deformation and has the potential to increase the formability of magnesium alloys. This book details the development of a thermo-mechanical treatment that yielded an elongation to failure of over 2000 percent for bulk ZK60 – the largest ever recorded. This was achieved by changing the mechanism of deformation from dislocation slip to grain boundary sliding. This book would interest people working in the field of magnesium alloy formability, equal channel angular extrusion and superplasticity research.