Crystallography and morphology of antiphase boundary-like structure induced by martensitic transformation in Ti-Pd shape memory alloy

An antiphase boundary (APB)-like structure in the B19 martensite of Ti-Pd alloy has been investigated by transmission electron microscopy. High-resolution and high-angle annular dark-field scanning transmission electron microscopy images demonstrate the presence of an APB-like contrast along the (001) basal plane of the B19 martensite. The contrast is not inherited from the APB with a displacement vector of the type R = (1/2)(111) in the B2 parent phase. These facts suggest that the boundary is induced by the local heterogeneity of atomic movements during the martensitic transformation. Therefore, we have newly proposed that the APB-like structure in the B19 martensite is defined as the displacive transformation-induced APB.