Coupled shear and shuffle modes during twin growth in B2-NiTi

Deformation twinning of B2 austenitic phase in NiTi has not been understood despite its significance. A number of experimental observations have been made, but these alone cannot explain the complex shears and shuffles that produce the twin. We propose that twinning can occur via (211) [111] shear and the proposed shuffle differs from previous work and is parallel to the twinning shear. We established a twin energy barrier which is lower compared the previously proposed twinning modes, and has a magnitude of 79 mJ/m². Hydrostatic pressure is found to alter this energy barrier and the coupling of shear and shuffle mechanism.