Effect of Ga concentration on twinning pseudoelasticity in Fe–Ga single crystals

Abstract

The effect of Ga concentration on the twinning pseudoelasticity in Fe–Ga single crystals with 20.0–24.4 at%Ga was examined. In Fe–20.0 to 24.4Ga (at%) single crystals, 2.2T-type pseudo-twins with {1 1 2} twin plane were formed during compression at low temperatures, especially at 93 K. The energy of the pseudo-twins was so high that the twins disappeared during unloading, resulting in the twinning pseudoelasticity. At 93 K, the amount of strain recovery caused by the twinning pseudoelasticity increased with increasing Ga concentration depending on the energy of the pseudo-twins. On the other hand, Fe–23.0Ga and Fe–24.4Ga single crystals with the D03 structure exhibited pseudoelasticity even at room temperature, which is based on reversible motion of 1/4[1 1 1] superpartial dislocations dragging antiphase boundaries. At 20.0 at%Ga, the twinning deformation was predominant at and below 173 K while large strain recovery due to the twinning pseudoelasticity at 24.4 at%Ga was observed only at 93 K. It is also noted that the stress–strain hysteresis at 93 K was greater at 24.4 at%Ga than at 23.0 at%Ga, which was closely related to a lattice distortion accompanying the pseudo-twin formation.