DEFORMATION PROPERTIES OF TINI SHAPE-MEMORY ALLOY

The basic deformation properties of pseudoelasticity and shape memory effect due to martensitic transformation and R-phase transformation we re investigated experimentally for TiNi shape memory alloy (SMA) wire subjected to various maximum strains. The properties of transformation temperature were discussed based on differential scanning calorimetry . The main results are summarized as follows. (1) The deformation prop erties of pseudoelasticity and shape memory effect were determined bas ed on a stress-temperature phase diagram in which stress and temperatu re were variables. The stress-temperature phase diagram is useful for the design of SMA elements. (2) If maximum strain was in the martensit ic transformation region, both reverse transformation stress and rever se transformation temperature were almost constant. Ii maximum strain was in the upswing region after completion of the martensitic transfor mation, reverse transformation stress decreased and reverse trans form ation temperature increased with an increase in maximum strain, result ing in the shift of the reverse transformation lines downward and to t he right.