Transmission electron microscopy study of the microstructure of B19 martensite in sputter-deposited Ti50.2Ni30Cu19.8 thin films

The martensite structures in Ti50.2Ni30Cu19.8 thin films were studied by transmission electron microscopy. The single-pair martensite morphologies with (0 1 1) or (1 1 1) twins are usually observed. (1 1 1) type I twins are dominant in the film annealed at 773 K, whereas (0 1 1) compound twins are dominant in that annealed at 973 K. The (0 1 1) twin width decreases dramatically when the annealing temperature changes from 773 to 973 K. The grain boundary precipitates in the films annealed at 973 K are responsible for these changes.