Effectof magnetic fields on martensitic transformations in ferrous alloys and steels

Abstract

The recent works carried out by the authors’ research group on magnetic field-induced martensitic transformations are reviewed, which are concerned with various kinds of ferrous alloys, such as Fe-Ni poly-and mono-crystals, invar and non-invar Fe-Ni-C polycrystals, disordered and ordered Fe-Pt polycrystals, ausaged Fe-Ni-Co-Ti polycrystals and paramagnetic Fe-Mn-C polycrystals. The works clarified influences of composition, the existence of grain boundaries, crystal orientation, invar characteristic, thermoelastic nature and austenitic magnetism on the magnetic field-induced martensitic transformations. In the work on the ausaged Fe-Ni-Co-Ti alloy, the appearance of “magnetoelastic martensitic transformation” was newly found. By taking into account the influences of composition, grain boundaries, crystal orientation, invar characteristic, thermoelastic nature and austenite magnetism, a new and exact equation was proposed to generally explain the shift of Ms temperature as a function of critical magnetic field to induce martensitic transformations in those alloys, which consisted of three terms of the Zeeman energy, high field susceptibility energy and forced volume magnetostriction energy. The new and exact equation was experimentally verified to hold in all the alloys studied. © 1989, The Iron and Steel Institute of Japan. All rights reserved.