Stress-Strain-Temperature Relationship Associated with the R-Phase Transformation in TiNi Shape Memory Alloy : Influence of Shape Memory Processing Temperature

The stress-strain-temperature relationship associated with the R-phase transformation in TiNi shape memory alloy is investigated experimentally and theoretically. The main results are summarized as follows. (1) The R-phase transformation showing a clear yielding stage in the stress-strain-temperature relationship appears at a certain shape memory processing temperature. (2) The R-phase transformation strip and the reverse transformation strip on the stress-temperature plane, which specify the characteristics due to the R-phase transformation are almost overlapping. Both transformation strips are narrow at high shape memory processing temperature. (3) The constitutive equation considering the volume fraction of the R-phase well describes the deformation behavior, such as the shape memory effect, pseudoelasticity and partial pseudoelasticity.