The in situ measurement of the effect of plastic deformation on the magnetic properties of steel: Part II – Permeability curves

Abstract We report measurements of the bulk magnetic properties of pearlitic steels recorded in situ during plastic deformation. The low-field total differential permeability was found to initially increase with increasing elastic tensile stress applied in the direction of the magnetic field. However, it was found to reach a maximum value well before the yield point and decreased rapidly after reaching that maximum. No qualitative change of behaviour was observed at the yield point. The initial increases in total differential permeability are attributed to the stress-induced removal of domains with magnetisation vectors that are approximately perpendicular to the field and stress direction. The subsequent decreases in total differential permeability are attributed both to stress-induced changes in the magnetic anisotropy and to new pinning sites generated during the plastic deformation process. The low-field reversible differential permeability appears to show similar behaviour with increasing stress, although the maximum value for this type of measurement is not as well defined. Measurements of the high-field total differential permeability decreased monotonically with stress in both the pre-yield and plastically deformed regions.