The methods of XRD, TEM and energy dispersive X-ray (EDX) are used to investigate the precipitiation process in Ni47Ti44Nb9 specimens annealed at 850 degC. It has been shown that a diffusional transformation takes place when the alloy is subjected to a long time heat treatment, around here most of the beta-Nb particles disappeared and a new precipitate (Ni,Nb)_3Ti with a h.c.p. structure (a=0.5133 nm, c=0.8376 nm. and c/a-1.63) was found, which is similar to Ni_3Ti in structure. The upper critical precipitation temperature of the alloy lies above 950 degC. It means that the presence of niobium inhibits the occurance of the precipitation. In addition, a coherent orientation relationship between the remaining beta-Nb precipitate and matrix was observed: (111)_beta-Nb//(111)_NiTi (110)_beta-Nb//(110)_NiTi
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