Resistance to strain-induced damage of an ultrafine-grained magnesium alloy deformed in superplastic conditions

An AZ91 alloy was processed by equal channel angular extrusion, leading to an important refinement of the microstructure. After optimised processing, the alloy was deformed in superplastic conditions and a mechanism of deformation was identified. Particular attention was given to the study of damage induced by superplastic strain. It is shown that despite a significant fraction of intermetallic compounds, the resistance to cavitation is particularly high. This resistance to damage is discussed in relation to the role played by grain boundary diffusion in ultrafine-grained magnesium alloys.