In-situ laser shock peening for improved surface quality and mechanical properties of laser-directed energy-deposited AlSi10Mg alloy

In the recent decades, the laser-directed energy deposition (L-DED) of aluminium alloy has encountered sig-nificant challenges owing to the defects and tensile residual stress. In this study, the in-situ laser shock peening method is employed for the first time to improve the surface quality and mechanical properties of L-DED-fabricated AlSi10Mg alloy. The physical mechanism of the compressive pressure on the pore defects is accounted for using the finite element method. The numerical results indicate that severe plastic deformation driven by the shock wave contributes to defect healing, and the maximum pressure plays a crucial role. The effects of surface laser shock peening (SLSP) and layer-by-layer laser shock peening (LLSP) on the densification, surface quality, including the roughness and residual stress, microstructure, and mechanical properties of the samples are experimentally studied. After the LLSP treatment, the surface quality and mechanical properties of the samples exceed those of common aluminium alloys fabricated by laser powder bed fusion (L-PBF). After the SLSP treatment, a compressive residual stress with a maximum value of 30 +/- 14 MPa is formed on the upper surface, and the LLSP treatment overcome the depth limitation of the affected zone. Furthermore, the LLSP treatment addresses the strength-ductility trade-off, and realizes an excellent combination of strength and ductility through grain refinement, dislocation strengthening, and compressive residual stress. Therefore, this work establishes the viability of in-situ laser shock peening for the rapid additive manufacturing of large-size aluminium alloys. Data Availability: The data used to support the findings of this study are available from the corresponding author upon request.

Automated summary

In this study, the in-situ laser shock peening method is used for the first time to improve the surface quality and mechanical properties of L-DED-fabricated AlSi10Mg alloy. The results show that severe plastic deformation driven by the shock wave contributes to defect healing, and the maximum pressure plays a crucial role. Surface laser shock peening (SLSP) and layer-by-layer laser shock peening (LLSP) have positive effects on the densification, surface quality, microstructure, and mechanical properties of the samples. The LLSP treatment addresses the strength-ductility trade-off and achieves an excellent combination of strength and ductility through grain refinement, dislocation strengthening, and compressive residual stress.