The effect of electric pulse aided ultrasonic rolling processing on the microstructure evolution, surface properties, and fatigue properties of a titanium alloy Ti5Al4Mo6V2Nb1Fe

Ultrasonic rolling processing (URP) can strengthen the material surface layer and enhance the material properties. However, the surface layer of work hardening induced by URP behaves like a hard shell that can restrict further strengthening of deeper material. The URP of Ti alloy Ti5Al4Mo6V2Nb1Fe strengthened its surface layer properties, but the material performance did not improve to a greater extent. In this study, electric pulse aided ultrasonic rolling processing (EPAURP) was utilized for the nanocrystallization of the surface layer and further improvement of the Ti5Al4Mo6V2Nb1Fe properties such as wear resistance, mechanical properties, and fatigue properties. The experimental results revealed the nanocrystallization of the surface layer through the introduction of electric pulse. The nanocrystallized surface layer was approximately 300 nm thick, and the size of the nanocrystalline was about 30 nm. In addition, the EPAURP induced the formation of a serious plastic deformation (SPD) surface layer, with thickness greater than that induced by the URP. The EPAURP reduced the defects and cracks in the surface and improved the fretting wear resistance, attributing to work-hardening and nanocrystallization. The tensile properties and fatigue properties improved after EPAURP owing to the smooth surface, higher compressive residual stress, and the nanocrystallization.