Possibility of Application of Magnetoacoustic Emission for the Assessment of Plastic Deformation Level in Ferrous Materials

The paper presents the results of an attempt to use the magnetoacoustic emission (MAE) signal for the nondestructive evaluation of plastic deformation levels in samples subjected to tensile loading. Four varied materials have been investigated: 13HMF, CSN12021 and P91 steels and commercially available Armco Iron. As it turned out various magnetic and magnetoacoustic properties of materials subjected to plastic tensile deformation behave in different ways for various materials, yet it is universally true that the steepness of the magnetic hysteresis loops decreases, thus leading to the increase in the separation of the “knee” portions of those loops. The MAE signal, being directly connected with the processes taking place for the magnetic field intensity at which those “knees” are observed (namely the 90^° domain wall creation/annihilation and movement) can be used for the detection of that increased separation. As a suitable parameter we propose either the MAE peak separation (if two maxima are visible) or the separation between the peaks obtained for increasing and decreasing magnetizing field. An important feature of those parameters is that in all the investigated materials we observe a monotonous increase of such separation.