Effect of ultrasonic shot peening on microstructure and surface corrosion resistance of WEDM-machined Ti6Al4V alloy

Wire electrical discharge machining (WEDM) of Ti6Al4V generates a recast layer of variable thickness on the material surface and introduces machining defects that degrade surface properties. This study investigates the effect of ultrasonic shot peening (USP) on the microstructural evolution of WEDM-processed surfaces and their corrosion resistance through numerical simulations and experimental analyses. Experimental results show that USP effectively reduces the number of microcracks and micropores on WEDM surfaces, decreases surface roughness (Ra) by 84.6%, and induces the formation of a ∼15 μm thick nanocrystalline layer, leading to an approximately 51.5% increase in near-surface microhardness and a corresponding 82.3% reduction in corrosion rate. The results indicate that USP improves the corrosion resistance of WEDM surfaces while preserving the recast layer, comparatively further enhancing the corrosion resistance of Ti6Al4V. This improvement is primarily attributed to surface quality optimization and the formation of gradient nanostructures through USP.