PHASE TRANSFORMATIONS IN Ti//2Ni//3 PRECIPITATES FORMED IN AGED Ti-52 At. Pct Ni.

The TiNi alloys of near equiatomic composition are one of the most technologically important shape memory alloys. The morphology and crystallography of transformation products of Ti//2Ni//3 in an aged Ti-52. 0 at. pct Ni alloy have been studied by optical and electron microscopy and electron diffraction. The crystal structure at room temperature is confirmed to be monoclinic. The sequence of transformation events was deduced to be as follows: parent phase (tetragonal) yields intermediate phase characterized by antiphase-like domain morphology (orthorhombic) yields low temperature phase characterized by needle-like domain morphology (monoclinic).