Effect of the ordering process on pseudoelasticity in Fe3Ga single crystals

The pseudoelastic behaviour of Fe3Ga single crystals with the D03 structure was investigated focusing on the annealing conditions and Ga content. In these D03–ordered Fe3Ga single crystals, uncoupled and paired 1/4[1 1 1] superpartial dislocations moved, dragging the nearest-neighbour and next-nearest-neighbour anti-phase boundaries (APBs), respectively. These APBs pulled back the superpartials during unloading, resulting in pseudoelasticity, though a martensitic transformation never occurred in the crystals. The amount of strain recovery increased with increasing Ga content up to 25.4 at.% when the crystals were annealed at 853–893 K within 10 h. In particular, nearly perfect pseudoelasticity with a recoverable strain of 5% was obtained at 24.2 and 25.4 at.% Ga after an appropriate heat treatment. Isothermal annealing in the D03 single phase region was effective in improving pseudoelastic properties. Moreover, the metastable D03 phase also exhibited pseudoelasticity, even if the (α + L12) or (D03 + L12) dual phase was thermally stable in the equilibrium state.