Enhancing high-temperature fatigue resistance of TC11 titanium alloy through combined plasma zirconizing and ultrasonic surface rolling

To boost the fatigue resistance characteristics of TC11 titanium alloy under thermo-mechanical coupling, the effects of plasma zirconizing (Zr), ultrasonic surface rolling process (USRP), and the plasma zirconizing followed by USRP treatment (Zr + USRP) on the high-temperature fatigue behavior of TC11 titanium alloy were investigated. The findings indicate that the plasma zirconizing induced microstructural weakening and stress concentration in surface regions, reducing the fatigue resistance at 500 ℃. The USRP treatment increased the fatigue limit of TC11 alloy samples by 5.5 % at 500 °C. And this enhancement was attributed to the surface layer microstructural refinement, surface roughness reduction, the introduction of compressive residual stress (CRS) field characterized by a deep distribution and high magnitude, which suppressed the initiation and propagation of fatigue cracks at high temperature. The high-temperature fatigue limit of the TC11 alloy was further increased by 7.3 % with the combined Zr + USRP treatment. Plasma zirconisation produced a solid solution strengthening effect pinning the dislocations formed treated by the USRP, improving the CRS field stability and microstructural stability of the TC11 alloy treated using USRP in the thermo-mechanical coupling environment. As a result, the initiation and propagation of fatigue cracks in TC11 alloy had been effectively prevented under high-temperature conditions.