Effect of heat treatment on pseudoelasticity in Fe–25.0 at.% Al single crystals

The pseudoelastic behaviour of Fe–25.0 at.% Al single crystals annealed in the D03, (α + D03), (α + B2) or B2 phase region was examined focusing on the dislocation and ordered domain structures. When large pseudoelasticity appeared in the crystals, 1/4[111] superpartial dislocations moved individually dragging the nearest-neighbour antiphase boundaries (NNAPB). During unloading, the superpartials were pulled back by the surface tension of the NNAPB resulting in pseudoelasticity. Large pseudoelasticity took place only in the D03-ordered crystals, while the crystals annealed in the (α + D03), (α + B2) or B2 phase region exhibited small strain recovery. The surface tension of the NNAPB in the D03 phase was higher than that in the B2 one resulting in the larger recoverable strain in the D03-ordered crystals. Since a specific type of ordered domain boundaries in the D03 phase played an important role in the pseudoelasticity, a coarsening of the ordered domains caused a decrease in strain recovery.