Miniaturized fatigue testing of gradient severe shot-peened LB-PBF AlSi10Mg: Influence of treatment sequence

Additively manufactured AlSi10Mg components are highly sensitive to surface quality, near-surface porosity, and residual stresses, which affect their fatigue performance. Shot peening (SP) is widely used as a post-treatment to improve surface integrity by inducing strain hardening and compressive residual stresses. Increasing peening severity can enhance the depth of the affected layer but also increases surface roughness and limits fatigue improvement. In this study, gradient severe shot peening (GSSP) was used to increase peening intensity while controlling the side effects. Two GSSP strategies were investigated to clarify the effect of peening sequence on the surface integrity and fatigue behavior of LB-PBF AlSi10Mg. The GSSP treatments were compared with the as-built (AB) condition and low-energy conventional shot peening (CSP). Surface morphology, apparent porosity, microstructural refinement, microhardness, residual stress and fatigue behavior were evaluated using miniaturized bending-fatigue specimens, while standard specimens were tested to assess the transferability of the selected GSSP condition. Fatigue strength increased from 57 ± 4 MPa, in the AB condition, to 83 ± 4 MPa, 110 ± 9 MPa, and 108 ± 4 MPa, after CSP, GSSP-1 and GSSP-2, respectively. Although the two GSSP treatments showed comparable mean fatigue strengths, GSSP-2 exhibited lower scatter, attributed to its more homogeneous surface morphology. Tests on standard specimens confirmed the beneficial effect of GSSP-2, with fatigue strength increasing from 65 ± 23 MPa to 150 ± 9 MPa. These results show that GSSP improves the fatigue response of LB-PBF AlSi10Mg, while treatment sequence controls surface homogenization and fatigue scatter.