Barkhausen Noise and Magnetic Properties of Plastically Deformed Silicon Steels

We present Barkhausen noise and magnetic measurements on two fully processed, nonoriented electrical steels which had been cold-rolled to thickness reductions of up to 60%. Both coercive field H_c and hysteresis loss W_h show an almost linear increase with thickness reduction up to the highest deformations. These changes are almost fully reversed after vacuum annealing for 2 h at 760°C. The hysteresis loss can be conveniently subdivided into high and low induction components as suggested by recent modelling. Electron back-scatter diffraction (EBSD) shows no texture change during initial phases of cold-rolling. Barkhausen noise measurements were obtained on both cold-rolled and annealed samples. The undeformed material shows a Barkhausen signature consisting of two small peaks which coalesce into one peak upon plastic deformation and thereafter grow steadily. Annealing the material brings back the two-peaked signature. These results are discussed and hypotheses are presented for the behavior of the Barkhausen noise.