The influence of heat treatment on the deformation properties of Ni$_{49}$Fe$_{18}$Ga$_{27}$Co$_{6}$ alloy crystals compressed in the [011] axis direction

Stress–strain diagrams ($\sigma$–$\varepsilon$ curves) have been studied during uniaxial compression of Ni$_{49}$Fe$_{18}$Ga$_{27}$Co$_{6}$ alloy single crystals in the [011] axis direction for the initial samples and those after 15-min annealing at 1373 K with subsequent quenching in water. It was established that the $\sigma$–$\varepsilon$ curves of initial crystals exhibited a one-stage character and showed a single stress decay, whereas the curves of heat-treated and quenched crystals displayed two stress decays. The shape-memory (SM) strain recovery on heating the compression-strained crystals showed an anomalous (burstlike) character. Investigation of the reproducibility of burstlike recovery of SM strain in a series of thermomechanical treatment cycles showed that the recovery took place in quenched crystals, whereas the temperature interval of SM recovery in the initial crystal grew from 1 to 12 K with increasing number of thermomechanical treatment cycles.