Microstructure Evolution and Strengthening Mechanisms of Mg-Steel Components Subjected to Multiple Micro Shot Peening Treatment

A surface modification through multiple micro shot peening have been performed on Mg-steel components. Application of shot peening was found favorable to the elimination of surface micro defects owing to severe surface plastic deformation induced by shot peening. Besides, multiple shot peening treatment transformed the residual tensile stress on the component surface into residual compressive stress, which was beneficial to inhibit the initiation and propagation of surface micro defects. Strain strengthening and grain refining were introduced into the shot peened joint, resulted in the notable increase in surface hardness. Compared with untreated component, the tensile strength of optimized Mg-steel specimen was significantly enhanced and raised about 28% to 244MPa, and fracture ultimately occurred in Mg alloy base material