Influence of Mn content on the magnetic properties and microstructure in Fe-Mn-Mo alloys

Abstract

The effects of the Mn content on the magnetic properties and microstructure of the Fe-Mn-Mo alloys have been investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, and Mossbauer spectroscopy. Experiments reveal that two types of thermal-induced martensites, epsilon (h.c.p.) and alpha' (b.c.c.) martensites, form in the as-quenched alloys and these transformations have athermal characters. epsilon and alpha' martensites coexist in the Fe-Mn-Mo alloys with 13.4-17.2 wt%Mn content. However, the Mn content affects considerably the amount of martensites and the amount of alpha' martensite decreases drastically while the amount of epsilon martensite increases with an increase in Mn content. Furthermore. only epsilon martensite appears in the case of 20.2 wt%Mn. Mossbauer spectra of the alloys reveal a paramagnetic character with a singlet for the gamma (f.c.c.) austenite and epsilon martensite phases and a ferromagnetic character with a broad sextet for alpha' martensite phase. With an increase in Mn content, the magnetic character of the Fe-Mn-Mo alloys changes and the ferromagnetic character disappears completely in the case of 20.2 wt%Mn. (C) 2009 Elsevier B.V. All rights reserved.