The martensite morphology in sputter-deposited thin films of Ti-48.5at%Ni was studied. During annealing (873K, 1h), fine Ti2Ni precipitates formed in the matrix of a TiNi phase. Electron diffraction techniques showed that (001) compound twins predominated, as internal defects, and lay in 3 orientations. There were 3 kinds of boundary among martensite (001) twinning domains: {113}-type, (001)||{111}-type and {111}-type. The wave-like {113}-type boundary was also of (001)||{111}-type from the atomic viewpoint. These matching planes beside the boundaries originated from the same close-packed planes in a body-centered cubic structure, and produced low-energy boundaries. The formation of (001) twinning was attributed to the impingement of growing martensite variants with Ti2Ni precipitates during martensitic transformation. In some local regions, (111) type-I or <011> type-II twinning could be found due to the relatively inhomogeneous distribution of precipitates.

Structure of Martensite in Sputter-Deposited Ti-Ni Thin Films Containing Homogeneously Distributed Ti2Ni Precipitates. J.X.Zhang, M.Sato, A.Ishida: Philosophical Magazine A, 2002, 82[7], 1433-49

       Table 4

    Diffusivity of Fe in Zr41Be22.5Ti14Cu12.5Ni10