Dilatation measurements for the study of the α/γ transformation in pure iron in high magnetic fields

Magnetic field processing is a new promising tool for the structural and functional control of materials. A significant potential exists for tailoring microstructures and impacting kinetics of phase transformation in steels. A high magnetic field modifies the Gibbs free energy. As a result, the phase diagram is shifted upwards so that the Ac1 and Ac3temperatures increase as the magnetic field is increased. In this work, a new device for the heat treatment and in situ control of the transformation is described. For the first time, a dilatation measurement is used to study the shift of the ferrite/austenite equilibrium in high magnetic field up to 16 T and to quantify the ferrite concentration during the transformation. Experimental results for the transformations in pure iron are presented. Comparisons are made with the expected values based on the Weiss molecular field model near the Curie point.