Surface nano-crystallization of AZ91D magnesium alloy induced by laser shock processing

Highlights: • The β-phase is decreased after laser shock processing, which is attributed to the grain refinement, micro-distortions and micro-strain development of crystalline. • Laser shock processing could induce surface nano-crystallization of AZ91D magnesium alloy. • The micro-hardness was improved after laser shock processing due to grain refinement and dislocation strengthening. - Abstract: The surface nano-crystallization of AZ91D magnesium alloy by laser shock processing (LSP) was studied in this paper. The microstructure in the surface region was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of LSP on the micro-hardness, surface topography and roughness were characterized by micro-hardness measurements and true color materials confocal microscopy (Axio CSM70). The micro-hardness of the surface nano-crystallization could be increased significantly by 86.2% after LSP. Surface nano-crystallization of AZ91D magnesium alloy induced by LSP was attributed to dislocation glide and mechanical twining.