The effects of ultrasonic nanocrystal surface modification on the fatigue performance of 3D-printed Ti64

3D-printed metals have great potential for application in the biomedical and the aerospace industries. Unfortunately, they suffer from poor surface finish, high porosity, and high tensile residual stresses, leading to inferior mechanical properties as compared with traditional cast or wrought metals. In this study, we introduce an innovative method, ultrasonic nanocrystal surface modification (UNSM), for the processing of a 3D-printed Ti-6Al-4V alloy. The surface finish, microstructure, residual stresses and mechanical properties of the samples before and after UNSM treatment were characterized and compared. It was found that the UNSM treatment resulted in much better surface finish, lower subsurface porosity, and a high magnitude of compressive residual stresses, leading to significant improvement in rotation bending fatigue performance.