The methods of XRD, TEM and energy dispersive X-ray (EDX) were used to inve
stigate the precipitation process in Ni47Ti44Nb9 specimens annealed at 850
degrees C. A diffusional transformation took place when the alloy was subje
cted to a long time heat treatment, most of beta-Nb particles disappeared a
nd a new precipitate (Ni, Nb)(3)Ti with an h. c. p. structure (a=0.512 2 nm
, c=0.837 6 nm, and c/a= 1.63) was found, which was similar to Ni3Ti in str
ucture. The upper critical precipitation temperature of the alloy was above
950 degrees C, it meant that the presence of niobium inhibited the occuran
ce of the precipitation. In addition, the orientation relationship between
the remaining beta-Nb precipitate and matrix was observed: [111](beta-Nb)//
[111](M), (110)(beta-Nb)//(110)(M).