Effect of internal stresses on the magnetic properties of non-oriented Fe–3wt.% Si and (Fe,Co)–2wt.% V alloys

The magnetic properties of soft magnetic materials are very sensitive to mechanical strengthening and especially to plastic straining. In a first approximation, the degradation of the magnetisation with the plastic strain level is supposed to be roughly isotropic. However, even after uniaxial strengthening, the multiaxial residual stresses induce directional fluctuations of these degradations. An experimental device has been created in order to study the effect of such internal stresses on magnetic behaviour. Experimental results are given for non-oriented Fe–3wt.% Si and (Fe,Co)–2wt.% V thin sheets. An attenuated effect of the strengthening is observed in the direction perpendicular to the applied stress whatever the direction of the latter inside the sheet plane. This phenomenon is discussed in terms of metallurgical defects (dislocation structures, grain boundaries and antiphase boundaries), internal stresses and magnetocrystalline anisotropy.