Magnetomechanical effects in iron and iron-carbon alloys

The variation of magnetization produced by the simultaneous application of magnetic fields and stresses (both compressive and tensile) has been studied for a range of iron-carbon alloys that have been subjected to various metallurgical treatments. For annealed, low carbon content materials in a small magnetic field, the magnetization-stress curves are unsymmetrical with respect to tension and compression. In the applied fields and stresses used, the asymmetry becomes less pronounced both for increase in residual internal stress and for increase in carbon content until, for cold-worked, high carbon content materials, curves are obtained that are sensibly symmetrical.

Up to now, two mechanisms have been used to explain the experimentally observed changes in magnetization, namely, that of stress-induced pressure p acting on 90° domain walls and that of large-scale changes in domain structure due to stress. It is demonstrated that these two mechanisms alone cannot account for the present observations. However, qualitative agreement is obtained over the whole range of alloys when account is taken of a third mechanism, that of stress-induced changes in the opposition term that must be in balance with p for domain wall equilibrium.