In-situ warm shot peening on Ti-6Al-4V alloy: Effects of temperature on fatigue life, residual stress, microstructure and mechanical properties

Shot peening (SP) is a matured surface enhancement technique to improve fatigue strength and fatigue lives of cyclically loaded metallic components at room temperature. In order to achieve enhanced beneficial effects beyond SP’s conventional performance, SP has been attempted at elevated temperatures or under tensile stress loading on spring steel with some success. In this work, SP on α/β Ti-6Al-4V alloys has been carried out when they were heated at elevated temperatures up to 400 °C. The effects of such in-situ warm SP on fatigue life of Ti-6Al-4V at different temperatures have been evaluated and correlated with respective development in compressive residual stress distribution, microstructure and hardness. The optimum in-situ warm SP condition was achieved at 100 °C after a trade-off between compressive residual stress relaxation and enhanced grain refinement, both of which are affected by thermal softening but to different degrees.