A novel lattice correspondence of B19 → B19′ transformation in Ti–Ni–Cu shape memory alloy thin film

In this study, we found a novel lattice correspondence of the B19–B19′ transformation in a Ti–Ni–Cu thin film: (1 1 1)B19′//(0 0 1)B19, [0, 1, 1]B19′//[1 0 0]B19. Near the coarse precipitate and the grain boundaries, the B19′ martensite forms with the novel lattice correspondence to product the (1 1 1) type I twinning instead of the usual (0 0 1) compound twinning. Crystallographic analyses show that the novel lattice correspondence results from the local stress concentration.