Abstract: Effect of different laser power density and shock times on residual stress and properties of the 7050-T7451 aluminium alloy, the specimens were treated by laser shock processing (LSP). The results show that, laser shock processing can increase the hardness of the specimen, and the hardness increases with the increase of shock times. The maximum surface micro-hardness can reach 172 HV0.05, which is increased by 17% compared with untreated specimen, and the depth of hardened influenced layer is 750 μm. When the laser power density is 7.28 GW/cm² and shocked for once, the surface roughness is 0.279 μm which is decreased by 22.5% compared with the original ground surface, and the roughness increases with the increase of shock times, but all are less than the original surface roughness. The laser shock processing can increase the residual stress of the specimen. When the laser power density is 7.28 GW/cm² and shock for three times, the maximum surface residual stress is －227.0 MPa. When the laser power density is 4.37 GW/cm² and shock for three times, the fatigue life of the specimen can up to 10⁶ cycles, which is increased by 2.3 times compared to that of the untreated specimen. The higher hardness and residual compressive stress by LSP can effectively prohibit cracking initiation and propagation and then enhance the fatigue property resistance of the 7050-T7451 aluminium alloy.

Key words: laser shock processing, 7050-T7451 aluminium alloy, microhardness, surface roughness, residual stress, fatigue property resistance