Effect of Al concentration on pseudoelasticity in Fe3Al single crystals

Pseudoelasticity in Fe3Al single crystals with different Al contents was investigated focusing on the dislocation configuration and the ordered domain structure. Giant pseudoelasticity only appeared in the D03-ordered Fe3Al single crystals, while the B2-ordered crystals and those with the disordered (alpha) phase exhibited small strain recovery. The amount of shape recovery in the D03-ordered crystals showed a maximum near 23.0at.%Al and decreased with increasing deviation from this Al concentration. In the D03 phase at 22.0-25.0at.%Al, 1/4[1 1 1] superpartial dislocations moved individually dragging the nearest-neighbour antiphase boundaries (NNAPB), while couplets of the superpartials were observed to bow out, dragging the next-nearest-neighbour antiphase boundaries (NNNAPB) in Fe-28.0at.%Al. In Fe-22.0-25.0at.%Al single crystals, the NNAPB pulled back the superpartials to decrease its energy during unloading, resulting in the giant pseudoelasticity. In contrast, the surface tension of the NNNAPB was lower than that of the NNAPB, leading to the small strain recovery in Fe-28.0at.%Al.