Nanoindentation and microstructure of Friction Stir Processed Die Cast Mg-Al-Zn alloy

Abstract

A high pressure die cast (HPDC) magnesium alloy was friction stir processed (FSP) at high rotation rates with
different advancing speeds. The friction stir process induced the disappearance of porosity, typical of the
HPDC process, and formation of very fine grain boundary phases. Nanoindentation was used to mechanically
characterize the different welded zones of interest, the thermomechanical heat affected zone (TMAZ), the stirred
zone (SZ), in the advancing and the retreating side, at different sheet section depths. Aging at high temperature
showed precipitates uniformly distributed inside the magnesium grains, due to the increased level of Al taken into
solid solution.