Effect of High Energy Shot Peening on the Microstructure and Mechanical Property of AZ31B Mg Alloy/HSLA350 Steel Lap Joints

Abstract

When using high energy shot peening (HESP) technology, the surface layer of the welded joints produced grain breakage and residual compressive stress. When the shot peening strength is the optimal parameter 0.10 MPa, the residual compressive stress reaches a maximum value of 74.02 MPa, dislocation density in welded joints increased significantly and the tensile shear strength of the joint was increased by 18.6% compared to the joint without HESP treatment (205 MPa), and the fracture position of the welded joint was located in the Al alloy base material, these were brought by fine grain strengthening and strain strengthening. When the shot peening strength was 0.05 MPa, the strength of the joint was also improved, but the fracture position of the joint was the same as that without HESP treatment, and they were all in the fusion zone. However, when the shot peening strength was further increased to 0.15 MPa, severe cracks appeared inside the joint, which deteriorates the strength of the Mg/steel joint.