Structure and mobility of <a>-type screw dislocation in presence of H in α-Ti from first-principles

Hydrogen has both negative and positive effects on the mechanical properties of titanium and titanium alloys. It has been reported that the plastic deformation of titanium is controlled by the -type screw dislocation and the principal slip plane is the prismatic plane. Herein, we employ first-principles calculations to investigate the modification of the -type screw dislocation core structures caused by addition of H and the interactions between them. It reveals that H is attracted to the pyramidal dislocation partial and tends to segregate to the dislocation region. Then, the slip paths of the screw dislocations along different slip planes in the H inserted Ti system are studied. Furthermore, the mechanism on how H affects the strength and plasticity of Ti under different H concentrations through the change of dislocation mobility is discussed.