Study of the paramagnetic-antiferromagnetic transition and the γ → ε martensitic transformation in Fe-Mn alloys

Abstract

The paramagnetic-antiferromagnetic transition and the γ → ε martensitic transformation of Fe-Mn (Mn 15–32 wt%) alloys have been investigated by resistivity, dilatometry and X-ray diffraction (XRD). The results show that paramagnetic-antiferromagnetic transition increases the resistivity and the volume of alloys, whereas the γ → ε martensitic transformation reduces the resistivity and volume of alloys. The A _f ^ε that was determined by the dilatometric method is not the temperature that ε martensites in the Fe-Mn alloys have reverse transformed to austenites completely. Mn additions reduce M _s, increase T _N and the lattice parameter of austenite in the Fe-Mn alloys. Both the antiferromagnetic transition and the γ → ε martensitic transformation lead to an increase in the lattice parameter of austenite. The lattice parameters both above T _N and below T _N decrease linearly with temperature. The lattice parameter below M _s increases first and then decreases. Moreover, the α (110) and ε (002) atomic planes in the Fe-15Mn-0.15C alloy are separated into two peaks: 2θ for ε(002) is 44.16°, 2θ for α(110) is 44.47°.