PREDICTIVE EQUATIONS FOR MARTENSITIC AND ANTIFERROMAGNETIC TRANSFORMATIONS IN FE-MN-AL-SI ALLOYS

The epsilon-martensite start temperature (M-s) and the Neel antiferrom agnetic transition temperature (T-N) of polycrystalline Fe-Mn-Al-Si al loys containing 30 or 35 wt% Mn, with additions of 1-7 wt% Al and 1-4 wt% Si, have been determined by electrical resistivity measurements, i n combination with lattice parameter changes and thermogravimetric ana lyses in an applied magnetic field. The compositional dependence of M- s and T-N is expressed in terms of linear equations fitted to the expe rimental results. The derived compositional dependence of M-s and T-N is used to predict possible shape memory alloys and to resolve discrep ancies concerning the maximum Mn concentration at which the epsilon-ma rtensite transformation can occur in binary Fe-Mn alloys, based on the suppression of this process by antiferromagnetic ordering. (C) 1997 C anadian Institute of Mining and Metallurgy.