Mössbauer and electron microscopy study of martensitic transformations in an Fe-Mn-Mo alloy

The kinetic, morphological, crystallographic, and magnetic characteristics of thermally induced martensites in Fe-13.4wt% Mn-5.2wt% Mo alloy were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Mössbauer spectroscopy. The experimental results reveal that two types of thermal-induced martensites, ε (hcp) and α' (bcc) martensites, are formed in the as-quenched condition, and these transformations have athermal characters. Mo addition to the Fe-Mn alloy does not change the coexistence of ε and α' martensites with the Mn content between 10wt% and 15wt%. Besides, Mössbauer spectra reveal a paramagnetic character with a singlet for the γ (fcc) austenite and ε martensite phases and a ferromagnetic character with a broad sextet for the α' martensite phase. The volume fraction of α' martensite forming in the quenched alloy is much more than that of the ε martensite.