Effect of layer-wise femtosecond laser shock peening on cracking growth in laser powder bed fused AA 7075

Though laser powder bed fused (LPBF) technology has been widely applied in various industries, it still suffers from the issues of residual stress deformation and cracking, etc. This paper introduced the layer-wise femtosecond laser (fs-laser) shock peening (FLSP) firstly, as far as the authors know, to the LPBF process with the aim of tailoring the residual stress and suppressing cracking. A verification experiment on AA 7075 demonstrated that the surface crack density was reduced by 39 % with a layer-wise FLSP. The crack suppression can be explained from two aspects. On one side, the residual tensile stress was tailored to near zero, decreasing the cracking growth motivation. On the other side, the grain size was decreased while the dislocation density was increased with the FLSP, increasing the cracking growth resistance. This study provides novel ideas for solving the problems of deformation and cracking in LPBF technology.