Crystallography of Fe–Mn–Al–Ni Shape Memory Alloys

Abstract

The microstructure of the martensite formed in Fe–Mn–Al–Ni alloys of varying composition, consisting of A2 austenite and A1-like martensite, was investigated by means of electron backscatter diffraction (EBSD). While sufficiently structured EBSD patterns clearly revealed a tetragonal distortion of the (twinned) martensite, robust indexing using Hough-transform-based methods were successful only by assuming a cubic symmetry of the martensite. It was shown that predictions made based on the Phenomenological Theory of Martensite Crystallography (PTMC) were well compatible with the experimental data, irrespective of the alloy composition. This includes a (near-)Pitsch orientation relationship and habit planes close to {110}A2.