Anomalous effect of Si additions upon the paramagnetic-to-antiferromagnetic transition entropy in fcc high-Mn steels

Fe–Mn based alloys with more 12% at. of Mn are usually called High-Mn steels. Several technological properties of High-Mn steels are explained by the presence of the fcc-hcp martensitic transformation. This transition is strongly affected by the para-to-antiferromagnetic ordering transition present in the fcc structure. The magnetic ordering temperature depends on the alloy chemical composition, and strongly stabilizes the fcc austenitic phase, leading to a decrease of the structural transformation temperatures. In several cases, this effect is strong enough to inhibit the martensitic transformation. In the present study, the effect on the magnetic transition of adding Si to high-Mn Fe–Mn alloys is analyzed. Calorimetric measurements are performed in order to obtain the entropy change associated to the magnetic ordering transition. The results are discussed in the light of the available information in the literature. Striking effects are reported, which indicate that Si addition strongly affects the driving force of the martensitic transition.