Coercivity and domain structure of nanograined Fe–C alloys after high-pressure torsion

• Published in: Journal of materials science 2008-06, Vol.43 (11), p.3775-3781
• Main Authors: Protasova, Svetlana G., Straumal, Boris B., Dobatkin, Sergei V., Goll, Dagmar, Schütz, Gisela, Baretzky, Brigitte, Mazilkin, Andrei A., Nekrasov, Alexei N.
• Format: Article
• Language: English
• Subjects: Ambient temperature; Annealing; Carbon content; Casting alloys; Cementite; Characterization and Evaluation of Materials; Classical Mechanics; Coercivity; Crystallography and Scattering Methods; Deformation; Domain walls; Eutectoid temperature; Grain size; Hysteresis loops; Intergranular and Interphase Boundaries in Materials; Magnetic properties; Magnetism; Materials Science; Pinning; Polymer Sciences; Solid Mechanics; Torsion
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-007-2394-z

The microstructure and magnetic properties of binary hypo- and hyper-eutectoid Fe–C alloys were studied. The investigations have been carried out on the samples in the as-cast state, after a long annealing at 725 °C and on the specimens after the high-pressure torsion (HPT). The deformation was carried out at the ambient temperature and the pressure of 5 GPa. The grain size after HPT is in the nanometer range. Long annealing leads to a drastic decrease of the coercivity in comparison with the as-cast alloys. In all alloys the coercivity H c increases with increasing carbon content. The distance L between pinning points for domain walls decreases with increasing carbon content. Increase of the coercivity and decrease of L are more pronounced below the eutectoid concentration. The coercivity of the nanostructured samples is higher than that of the as-cast alloys. Due to the pinning of domain walls by the cementite particles, the hysteresis loop in the coarse-grained alloys both in as-cast and annealed states has a narrowing near the zero magnetization.