Improvement in Rotary Bending Fatigue and Ultrasonic Fatigue Behavior of Ti-6Al-4V STA alloy by Ultrasonic Nanocrystal Surface Modification Technique

This study investigates the effectiveness of ultrasonic nanocrystal surface modification (UNSM) technique on the mechanical properties and rotary bending fatigue (RFT) and ultrasonic fatigue tests (UFT) of solution-treated and annealed (STA) Ti-6Al-4V alloy. Fatigue data and fracture modes are investigated and compared for the untreated and UNSM-treated Ti-6Al-4V STA alloy specimens. Both RFT and UFT results exhibited an improvement in the fatigue life of Ti-6Al-4V STA alloy which may be attributed mainly to the UNSM-induced compressive residual stress, micro-hardness, and nanograin in the subsurface of the material. The possible mechanisms of fatigue life and fracture types are discussed in this study.