Enhancement of grinding titanium alloy fatigue performance via synergistic effect of low surface roughness and gradient microstructure

To enhance the machining efficiency and fatigue performance of titanium alloy components, this study proposes a large-depth-of-cut creep-feed belt grinding-polishing hybrid process. By optimizing surface/subsurface integrity, this process achieves nearly a fivefold improvement in the fatigue life of Ti-6Al-4V alloy. The key innovation lies in revealing the synergistic anti-fatigue mechanism of low surface roughness and gradient microstructure: ultralow surface roughness (Ra 0.26 μm) effectively eliminates stress concentration sources; gradient-distributed compressive residual stresses significantly counteract external tensile stresses; subsurface grain refinement (average grain size refined to 3.8 μm) effectively suppresses crack initiation and propagation. This hybrid process enables both efficient material removal and high-integrity surface preparation on a single platform, providing new theoretical foundations and technical pathways for fatigue-resistant manufacturing of titanium alloys.