Study of the paramagnetic-antiferromagnetic transition and the gamma ->epsilon martensitic transformation in Fe-Mn alloys

The paramagnetic-antiferromagnetic transition and the γ → e 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 → e martensitic transformation reduces the resistivity and volume of alloys. The Afe that was determined by the dilatometric method is not the temperature that e martensites in the Fe-Mn alloys have reverse transformed to austenites completely. Mn additions reduce Ms, increase TN and the lattice parameter of austenite in the Fe-Mn alloys. Both the antiferromagnetic transition and the γ → e martensitic transformation lead to an increase in the lattice parameter of austenite. The lattice parameters both above TN and below TN decrease linearly with temperature. The lattice parameter below Ms increases first and then decreases. Moreover, the α (110) and e (002) atomic planes in the Fe-15Mn-0.15C alloy are separated into two peaks: 2θ for e(002) is 44.16°, 2θ for α(110) is 44.47°.