The effects of microstructural and chemical surface gradients on fatigue performance of laser powder bed fusion AlSi10Mg

Internal and surface imperfections are known to reduce the fatigue strength of parts fabricated by laser powder bed fusion (LPBF). Post-treatment can play a key role to ameliorate the adverse effects of these defects. In this study, severe vibratory peening, as a novel surface treatment based on severe plastic deformation, was applied for the first time on LPBF material. The effects of this mechanical surface treatment were investigated individually and in combination with heat treatment on microstructural and mechanical properties of V-notched LPBF AlSi10Mg samples. The results revealed the simultaneous formation of microstructural and chemical gradients on the surface layer of the mechanically treated samples, resulting in remarkable mechanical properties’ improvement. In addition, the hybrid thermal and mechanical post-treatment significantly improved the fatigue life compared to the as-built condition, through affecting multiple physical phenomena regarding surface and subsurface characteristics.