Shape memory characteristics and superelasticity of Ti–45Ni–5Cu alloy ribbons

Ti–45Ni–5Cu (at.%) alloy ribbons have been fabricated by melt spinning at various melt spinning temperatures with a linear velocity of 31.0 m/s, and shape memory characteristics and superelasticity were investigated by means of thermal cycling tests under constant load and tensile tests. The ribbons obtained at the melt spinning temperatures above 1673 K showed two-stage deformation corresponding to the B2-B19-B19′ transformation. The temperature gap between M ′ s (the B2-B19 transformation start temperature) and Ms (the B19-B19′ transformation start temperature) increased with increasing the melt spinning temperature. Transformation hysteresis associated with the B2-B19 transformation was measured to be about 12 K, irrespective of the melt spinning temperature. The ribbons with the melt spinning temperature higher than 1723 K showed perfect superelasticity. Stress hysteresis associated with the B2-B19 transformation was less than 45 MPa, which was ascribed to a formation of single-pair martensitic variants in each grain.