New dislocation dissociation accompanied by anti-phase shuffling in the α″ martensite phase of a Ti alloy

Martensite phase plays a crucial role in the shape memory effect and superelasticity. In this study, a new dislocation dissociation was found in the α″ martensite phase of a Ti-based biomedical shape memory alloy by systematic transmission electron microscopy analysis and first-principles calculations. The slip direction of dislocation was along 〈101〉, which was recently found in a single-crystalline martensite fabricated using stress-induced martensitic transformation. The 〈101〉 dislocation dissociated into two partial dislocations, and the Burgers vector for both partial dislocations was equal to 1/2<101>. A planar fault with an anti-phase shuffling of basal plane was observed between the dissociated partial dislocations. The dissociation reaction of the 〈101〉 dislocation was summarized as 〈101〉 → 1/2<101> + anti-phase shuffling boundary + 1/2<101>. Most of the observed dislocations were in the form of screw dislocations, and the dissociated partial dislocations were twisted around the dislocation line.