Study of R-phase transformation in a Ti–50.7at%Ni alloy by in-situ transmission electron microscopy observations

The R-phase transformation in a Ti–50.7at%Ni alloy was investigated by in-situ transmission electron microscopy (TEM) observations using double-tilt cooling stages, and the incommensurability of 1/3 diffuse scattering in the process of the transformation was examined by using imaging plates. It is shown that the incommensurate diffuse scattering exists in the parent phase within a wide temperature range above the Rs temperature and that the incommensurability decreases with decreasing temperature. The R-phase transformation starts at the Rs temperature where the electrical resistance starts to increase and the R-phase is commensurate even in the state just after formation.