Effect of laser shock peening on microstructure and fatigue behavior of laser welded 7075 aluminum alloy

7075 aluminum alloy has high strength but poor weldability, even though applying laser welding, welded 7075 aluminum alloy still shows poor fatigue properties. In this study, laser shock peening (LSP) is used in the welded zone and the heat affected zone to improve the fatigue properties of the welded joints. The surface roughness, hardness, fatigue crack propagation and tensile with digital image correlation tests are carried out, and the microstructure is observed by scanning electron microscope and electron back scatter diffraction. Results show that the hardness values, proportion of high angle grain boundaries and grain dislocation density are increased, so that the higher energy LSP can significantly improve ultimate tensile stress and fatigue crack propagation behavior of welded joints. Meanwhile, the higher energy LSP significantly decreases surface roughness in the welded zone of welded joints.