T. Itsukaichi et al., MECHANICALLY ALLOYED NI50TI50 AND ITS TRANSFORMATION BY THERMAL TREATMENTS, Journal of Materials Science, 29(6), 1994, pp. 1481-1486
Amorphous powders have been obtained by mechanical alloying (MA) equia
tomic powder mixtures of nickel and titanium. The amorphous phase thus
formed decomposes upon heating first into the cubic B2 NiTi intermeta
llic compound; however, further heating promotes the precipitation of
the intermetallics Ni3Ti and NiTi2. These transformations are shown to
occur also in mechanically ground (MG) NiTi wire, but not in this sam
e material exempted from ball-milling processing. It is suggested that
this unique behaviour is brought about by the particular structural f
eatures of the MA or MG powders, which promote the otherwise sluggish
decomposition of B2 NiTi.