Molecular dynamics study of interactions between prismatic < a > slip and oxygen-segregated twin boundaries in a-Ti

Oxygen affects mechanical properties of alpha-Ti through significantly changing slip and twinning behavior of alpha-Ti. The strengthening mechanisms of oxygen do not simply depend on its contents, but also depend on its segregation states. For the achievement of optimal balance between strength and ductility of Ti-O alloy, to understand the fundamental effect of oxygen on slip and twinning behavior of alpha-Ti is important. In the present study, we performed molecular dynamics simulations to investigate the effect of solid solution oxygen on the interactions between prismatic screw (a ) slip and the {1012} and the {1011} twin boundaries of alpha-Tiunder various oxygen contents and segregation states. For the interactions with the {1012} twin boundaries, slip transmission or cross-slip occurred depending on oxygen contents. The difference of dislocation reactions can be explained by the boundary strength and the critical resolved shear stress of basal and pyramidal (a ) slips within matrix region. For the interactions with the non-segregated {1011} twin boundary, twinning dislocations were generated. The external stresses required for the generation of twinning dislocations and the dislocation reactions were quite different depending on the oxygen segregation sites. The atomic arrangement of octahedral sites adjacent to the twin boundary is distorted and became non-octahedral sites after the twinning dislocations were generated. Thus, for the {1011} twin boundaries, the effect of oxygen strongly depends on whether segregation sites of oxygen will change into non-octahedral sites or not.