Phase Transitions and Shape Memory in NiTi

摘要: The “premartensitic” transformation of the B2 phase in NiTi was studied using electrical resistance measurement, X-ray diffraction, and shape-change effects. degree rhombohedral distortion that change show similar temperature dependence. In particular, whenTR » Ms, this encompasses a narrow region rapid increase just belowTR, followed by an extended range levelling off. onset martensitic is not necessarily preceeded distortion, latter proceeds continuously belowTR persists throughout martensite range. Thus three kinds can occur: ai R, M, R M; precursory phenomenon. Observations on two-way memory (TWM) its correlation to changes leads conclusion >Ms, TWM comprised two stages. On cooling, → responsible for initial stage, which thermally reversible without hysteresis. second stage TWM, due formation, shape change, but with thermal It also suggested heating, contribute primary effect NiTi.