The X-ray diffraction intensity vs. temparature curves have been measured directily by method of constant angle scanning for parent phase

martensite and R-phase in NiTi alloy respectively. On heating and cooling

two stages have been found in variation of X-ray diffraction intensity of parent phase. On cooling

the first stage of diffraction intensity reduction corresponds to lattice unstability

but the second one corresponds to normal martensitic transition and R- transition. The two stage curve of diffraction intensity becomes to one stage curve under action of load. This phenomenon can be explained by transition temperaturc shifting when alloy undergoes a thermal cycling under load.