Abstract
TiNi intermetallic compound, which is the most important shape memory material, is industrially manufactured with the combustion synthesis process by using the heat of formation of Ti and Ni starting elemental powders. One kind of specimen with Ni-rich composition from stoichiometric value (Ti:Ni=1:1), 51.6 atomic%Ni, which shows the superelasticity at room temperature, is produced because the superelastic material is much in demand. In the present paper, the influence of the heat treatment conditions on the transformation temperatures of the specimen is mainly investigated from the viewpoint of practical use. The tendency of the transformation temperatures are divided into two regions, those are in the heat treatment temperatures under 800K and above 800K. The transformation temperatures decrease with the increase in heat treatment temperature up to 800K. In this case, it is not so dependent on the heat treatment time. The heat treatment temperature above 800K becomes a transition region where the transformation temperatures show a tendency to increase. In this case, the transformation temperatures show the tendency to increase with the heat treatment time. The transformation temperatures increase because Ti3Ni4 precipitates and Ni content in the matrix decreases in the heat treatment temperature region above 800K.
