Structure of the alloy Ti50Ni48.7Co1.3

The structure of the R phase of the alloy Ti50Ni48.7Co1.3 was determined by the crystallogeometric analysis of martensitic transformations in titanium nickelide. This analysis is based on the concept of cooperative thermal vibrations of the (110)-like planes in the b.c.c. and B2 structures and their freezing (transformation to static displacements) at the point of the phase transition. The space group of the R phase is trigonal P31m with a hexagonal Bravais lattice. The validity of the R-phase structure determination is confirmed by an X-ray diffraction pattern that was obtained at room temperature using Cu K alpha radiation. The Rietveld procedure was used to compare the calculated and experimental X-ray diffraction patterns. The proposed structural model of the R phase agrees satisfactorily with the experimental data.