Cyclic isothermal stress-induced transformations in high temperature Cu–13.1Al–4.0Ni (wt.%) shape memory alloy single crystal wires

Abstract

Isothermal stress-induced transformations in Cu–13.1Al–4.0Ni (wt.%) single crystal wires were studied up to an overall strain of 8.62% and cycled until stabilization at test temperatures in the range, 25–175 °C, after the material had been heated from room temperature. A total of 26 cycles were needed for stabilization. A partial phase diagram of the cycled material is then developed. A second set of tests on the same material was carried out by heating the material to 175 °C and then cooling it to the test temperature, prior to the mechanical tests. A total of 18 cycles were needed for stabilization. Two-way shape memory strain started to accumulate from the 39th mechanical cycle, rising to as high as 3% at the end of the 44th cycle. No plastic strain was observed during the entire sequence of 44 cycles.