2016 Volume 57 Issue 3 Pages 269-277
In the present study, Ni content dependence of martensitic transformation behavior in Ti50−xNi40+xCu10 alloys (x = 0.0–3.0) was investigated, and then the superelastic behavior of a x = 2.4 alloy was examined at low temperatures. The Ti50−xNi40+xCu10 alloys are in B2 single-phase up to x = 2.4 at 1373 K. The B2/B19 and B19/B19′ transformation temperatures decrease with increasing x and the lowest martensitic transformation starting temperature of 125 K was detected. In the alloys with Ni compositions over x = 1.4, a pre-martensitic “intermediate” phase was detected by thermoanalysis measurements. While the middle eigenvalue λ2 is close to 1.0, which was found to be independent of the Ni content, the thermal hysteresis, Thys increases with increasing Ni content. This is explained by the drastic decrease in transformation entropy change. Although starting to drastically increase at temperatures below 100 K, the temperature dependence of stress hysteresis in compression testing is basically smaller than that in Ti48.2Ni51.8 binary alloy.
