Pseudoelasticity in Fe3Al single crystals

Single crystals of the D0(3)-long-range-ordered intermetallic compound Fe3A l have been compression tested in the temperature range 213-493 K. The orie ntations of the axes of the crystals covered the entire standard triangle. All of them were pseudoelastic (i.e. superelastic) in the lower part of the quoted temperature T range; during unloading, an appreciable part of plast ic deformation was recovered. In the investigated range of T, the yield str ength as well as the amount of the strain recovered during unloading decrea sed as T was raised. Transmission electron microscopy revealed that these d ecreases are caused by a change in the relevant dislocation processes. At l ower temperatures, there are very widely spaced partial dislocations with B urgers vectors of the type (a(0)/4)[111], where no is the lattice constant. At higher temperatures, four such partial dislocations glide together form ing a perfect dislocation. In the upper range of T, crystals with the [111] orientation showed a different behaviour; single (a(0)/4)[111] partials cr eated narrow slip bands by gliding in:closely spaced planes. On the basis o f the different temperature dependences of firstly the frictional stress ex perienced by each (a(0)/4)[111] partial and secondly its cross-slip probabi lity, a tentative interpretation of the experimental results is suggested.