The effect of plastic deformation and residual stress on the permeability and magnetostriction of steels

We report the results of magnetic measurements performed on specially prepared steel samples. These measurements were made after the samples had been uniaxially plastically deformed and the applied stress removed. The observed magnetic behaviour included characteristic changes in the shape of the hysteresis loops and total differential permeability curve, a linear response of the coercive field to the prestress and a lack of continuous changes in the magnetostrictive behaviour with increasing prestress. The results of the experiments indicated that residual stress did not play an important role in the observed variation of these magnetic properties. The changes in the magnetic behaviour were attributed instead to the generation of pinning sites during the plastic deformation process and the different effects of these pinning sites on 180 degrees and 90 degrees domain walls and magnetisation vector rotations. It was also found that the prestress applied to the samples before measurement, rather than the resulting strain, was the factor that directly affected the magnetic parameters. (C) 2000 Elsevier Science B.V. All rights reserved.