Surface strengthening mechanisms of laser shock peening additive manufacturing CuSn alloys: Experimental and numerical simulation investigations

Laser shock peening (LSP) is a widely used in the post-additive manufacturing industry for inducing compressive residual stress (CRS) and healing defects. Compared to traditional surface strengthening techniques, LSP provides the advantages of high machining precision and flexibility, achieving surface strengthening with minimal surface damage. This study conducted a series of LSP experiments on the additively manufactured Cu-Sn alloy with varying single pulse energy, which achieving defects healing and introducing CRS into surface. The experimental results confirm that the surface microstructure forms a finely-distributed layer within a uniform distribution after LSP. The surface hardness increased from 134(+ 2.5) HV to 222(+ 3.3) HV at maximum, and the CRS of -316 (+ 85) MPa was introduced into the surface of sample. Moreover, after LSP treatment, the porosity was reduced from 5.4(+ 1.5) % to 1.3(+ 0.4) %, the surface corrosion resistance improved approximately 6.6-fold. Importantly, we propose a more accurate finite element model (FEM) for the spatial-temporal distribution of shock pressure and analyze the residual stress distribution caused by different laser energies. The experimental and FEM results have better agreement, which confirms the reasonability of the method. The method provides a theoretical approach for the fields related to laser processing such as laser forming and laser-induced surface structure.