Alignment of Two-Phase Structures in Fe-C Alloys by Application of Magnetic Field

Application of magnetic fields up to 12 T during the α → y inverse transformation in Fe-0.1 mass%C and Fe-0.6 mass%C alloys was found to yield two-phase microstructures with the paramagnetic y phase aligned as chains or columns along the direction of the applied magnetic field in the matrix of the ferromagnetic α phase. The alignment was found to be independent of the rolling directions during the preparation of specimens. Further, it was unrelated to the microstructure of the prior y phase. This phenomenon is explained by a model of the coalescence and growth of the nuclei of the inverse y phase under the dipolar interactions in the background of the ferromagnetic α phase. The applied magnetic lield raises the inverse transformation temperature by 1°C/T in accordance to the magnetic free energy change.