Mössbauer Spectroscopy, Dilatometry and Neutron Diffraction Detection of the ɛ-Phase Fraction in Fe–Mn Shape Memory Alloys

The results of a Mössbauer spectroscopy (MS) and a neutron diffraction (ND) study carried out on a set of Fe–Mn alloys quenched from high temperatures are reported. Upon quenching the high temperature stable phase FCC (γ) together with metastably retained HCP-(?) phase are formed. The lattice parameters obtained using ND are in excellent agreement with previous results of the literature. The phase fractions obtained from MS are coincident, within experimental errors, with those extracted from ND, with exception of the case of an alloy with the lowest Mn content (16.8 at.% Mn). That situation can be associated with the occurrence of a high density of stacking faults (SF) in the γ phase or to the presence of a paramagnetic γ phase. ? phase fractions obtained from MS and ND decrease smoothly with Mn content but are always larger than the values reported in literature resulting from dilatometry.