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 were investigated experi-mentally 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 properties of pseudoelasticity and shape memory effect were deter-mined based on a stress-temperature phase diagram in which stress and temperature were variables. The stress-temperature phase diagram is useful for the design of SMA elements. ( 2 ) If maximum strain was in the martensitic transformation region, both reverse transformation stress and reverse transformation temperature were almost constant. If maximum strain was in the upswing region after completion of the martensitic transformation, reverse transformation stress decreased and reverse transformation temperature increased with an increase in maximum strain, resulting in the shift of the reverse transformation lines downward and to the right.