Fracture surface characterisation of friction stir processed magnesium alloy after mechanical tests

A high pressure die cast Mg-9%Al-1%Zn alloy was friction stir processed at two high rotation rates and advancing speeds. Tensile tests were performed at higher temperature to study the mechanical properties of the microstructure induced by the friction stir process. Fracture surfaces resulting from tensile tests were observed by scanning electron microscopy and investigated by microanalysis. The fracture occurred in the tmaz and inside the stirring zone, depending on deformation conditions (temperature and strain rate). The morphology of the fracture surface varied from ductile to brittle in the same sample depending on phase type. Microhardness was measured on cross sections perpendicular to the advancing direction of the stirring pin, at various depth levels, before performing tensile tests to estimate the attitude of a single region to be deformed.