Effect of Laser Shock Peening on micro-structure and mechanical properties of Friction Stir Welded CuCrZr sheets

Friction stir welding (FSW) of CuCrZr sheets was performed and Laser Shock Peening (LSP) was carried out as a post-weld surface treatment. Effect of LSP on hardness, tensile and fatigue strength was investigated. Depth of compressive residual stress in base material increased from 550 mu m to 700 mu m when the number of LSP shots was increased from one to five. However, noticeable change in surface residual stress could not be observed which is attributed to the saturation of dislocation density or plastic deformation at the surface. An increase in yield strength up to similar to 35% as well as an improvement in the fatigue life up to similar to 70% after LSP could be achieved for base and FSW specimens. Increase in low angle grain boundaries after LSP indicates the increase in substructure induced by plastic deformation. A quantitative analysis using grain boundary misorientation and kernel average misorientation was used to understand microstructural changes due to the LSP and correlate it with the mechanical properties.