Anomalous behavior of curves of pseudo-elastic deformation of Ni–Fe–Ga–Co alloy crystals as a result of interphase stresses

The compression diagram of Ni$_{49}$Fe$_{18}$Ga$_{27}$Co$_{6}$ alloy crystals in the [011] direction was studied until full shape memory strain at various temperatures in the range of 259–340 K. It is found that all load curves are anomalously shaped and contain portions of sharp and gradual decreases in deformation stresses. Simulation of pseudo-elastic stress–strain curves within the theory of diffuse martensitic transitions, describing not only equilibrium of phases, but also the kinetics of the transition between them, shows that elastic interphase stresses during martensitic reactions $Ll_{2}$ $\to$ 14$M$ and 14$M$ $\to$ $Ll_{0}$ characteristic of this alloy can be responsible for the extraordinary shape of compression diagrams.