Effect of ultrasonic surface rolling process on hydrogen embrittlement behavior of TC4 laser welded joints

Some key structural parts made of welding titanium alloys usually serve in hydrogen environment in aerospace, ship building and chemical industries. To investigate the hydrogen embrittlement (HE) behaviors of the welded titanium alloy joints and the impact factors, the TC4 titanium alloy joints welded by laser welding method were first treated by ultrasonic surface rolling process (USRP). Then, slow-rate tensile tests were conducted under electrochemical hydrogen charging condition to compare the mechanical properties of the TC4 laser welded joints before and after USRP. On this basis, the HE behaviors and mechanisms of the USRP-treated TC4 laser welded joint and the USRP-untreated one were discussed in detail. The results show that USRP could significantly improve the anti-hydrogen embrittlement behaviors of the TC4 laser welded joint, which could be attributed to the grain refinement and residual compressive stress in the deformation layer induced by USRP. The results of this paper provide a theoretical basis for the design of anti-hydrogen embrittlement metal materials.