Abstract
Relation between oxygen content and martensitic transformation temperature of the TiNi compacts prepared by a blended elemental approach has been studied. In this experiment, it was found that the Ms temperature decreases linearly with increasing oxygen content in the composition range less than 5200 p.p.m. of oxygen and that the precipitates which have fee structure with 11 Å of lattice constant exist appearently in the alloys containing more than 2700 ppm of oxygen. All experimental results obtained seem to suggest that the composition of the precipitates is Ti4Ni2O. Consequently, the decrease in Ms temperature could be attributed to the enrichment of nickel in matrix induced by the precipitation.
In order to pull up the Ms temperature toward the same level of that obtained in ingot materials, the effect of aging on the Ms temperature and that of excess addition of titanium powders in preparing the TiNi compacts have also been investigated. Both attempts were confirmed successfully to be useful for raising the Ms temperature.
