Influence of micro-shot peening and traditional shot peening on fatigue performance and fracture behaviors of Ti-6Al-4V alloy

Ti-6Al-4V alloy is subjected to complex environmental conditions, often requiring enhanced fatigue performance in engineering applications. This study provides a comparative analysis of the effects of micro-shot peening (MSP) and traditional shot peening (TSP) on the fatigue performance of Ti-6Al-4V alloy. The results indicate that TSP specimens develop a work-hardened layer with high hardness and elevated compressive residual stress (CRS) on the surface, whereas MSP specimens exhibit lower surface roughness and a grain refinement layer with a higher degree of refinement and more uniform grain distribution. Fatigue testing revealed that, compared to unpeened (UP) specimens, the fatigue strength of MSP and TSP specimens increased by 42 % and 17 %, respectively, after 2 × 10⁷ loading cycles. Shot peening modified the fracture mechanisms of the titanium alloy, introducing a critical stress below which crack initiation shifts from the surface to the subsurface. MSP specimens demonstrated a higher critical stress, resulting in significantly longer fatigue life compared to TSP specimens.