Multimode pseudoelasticity in Fe–23.8 at% Ga single crystals with D03 structure

Pseudoelastic behaviour of D03-ordered Fe–23.8 at% Ga single crystals subjected to different heat treatments was examined focusing on the deformation mode. There existed three kinds of deformation modes in the crystals depending on the heat treatment: stress-induced martensitic transformation, dislocation glide and twinning which had a potential to show large pseudoelasticity. Numerous martensites with the 14M structure were stress-induced during loading and disappeared during unloading resulting in perfect pseudoelasticity with small stress–strain hysteresis. On the other hand, 1/4[111] superpartial dislocations dragging the antiphase boundaries (APB) moved backward during unloading due to the APB tension, which also led to large strain recovery. Twinning and untwinning of 2.2T-type pseudo-twins accompanying both a serrated flow and a clicking sound were also responsible for the pseudoelasticity. It was also found that the pseudoelastic behaviour associated with the three deformation modes was strongly affected by stress sense and loading axis.