Martensitic transformation in NiTi investigated by synchrotron X-ray diffraction

Thermoelastic martensitic transformation of equiatomic NiTi has been investigated by synchrotron X-ray diffraction. The SR-source VEPP-3 was used to obtain X-ray patterns in a wide range of diffraction angles simultaneously, while heating or cooling. Diffraction angle resolution of the parallel single-coordinate detector was 0.008°, and the wavelength was 0.14879 nm. At the same time the parameters of the B2, R, B19′ phases have been determined and compared with literature data. We observed both reversible changes of the parameters b and c of the unit cell of B19′-martensite, evolution of the doublet reflex (202) and (202) of the R-phase, and volume effects under transformation. It has been demonstrated, that martensite preferably appeared in the more loose lattice rather than in an equilibrium state.