Crystallographic orientation relationships in the α→γ′ martensitic transformation in an Fe–Mn–Al–Ni system

The Fe43.5Mn34Al15Ni7.5 (at.%) alloy exhibits outstanding pseudoelastic behaviour over a wide range of temperatures. This alloy undergoes an unusual martensitic transformation from a disordered body-centred cubic (α) parent phase to a face-centred cubic (γ′) product phase. In the present work, the orientations of the parent and product phases for quenched samples were analysed by electron backscatter diffraction. Bain, Kurdjumow–Sachs, Pitsch, Nishiyama–Wassermann and Greninger–Troiano orientation relationships between the parent and product phases were compared with experimental results. The Pitsch relationship appears to be the most suitable to describe the α→γ′ martensitic transformation. This result provides experimental support to the dislocation-based heterogeneous Bogers–Burgers type transformation mechanism. No indications of variant selection were detected in the thermally activated transformations.