Impact of plastic deformation on magnetoacoustic properties of Fe–2%Si alloy

The paper presents the results of a complementary study including magnetic hysteresis loops B(H), magnetic Barkhausen noise (MBN) and magnetoacoustic emission (MAE) signals measurements for plastically deformed Fe–2%Si samples. The investigated samples had been plastically deformed with plastic strain level (εp) up to 8%. The properties of B(H) loops are quantified using the coercivity HC and maximum differential permeability μrmax as parameters. The MBN and MAE voltage signals were analysed by means of rms-like voltage (Ub and Ua, respectively) envelopes, plotted as a function of applied field strength. Integrals of the Ub and Ua voltages over half of a period of magnetization were then calculated. It has been found that HC and integrals of Ub increase, while μrmax decreases monotonically with increasing εp. The MAE (Ua) peak voltage at first decreases, then peaks at εp≈1.5% and finally decreases again. The integral of the Ua voltage at first increases for low εp and then decreases for εp>1.5%. All those various dependence types suggest the possibility of detection of various stages of microstructure change. The above-mentioned results are discussed qualitatively in the paper. Some modelling of the discussed dependency is also presented.