Effect of tensile deformation on micromagnetic parameters in 0.2% carbon steel and 2.25Cr-1Mo steel

The influence of prior tensile deformation on the magnetic Barkhausen emission (MBE) and the hysteresis (B-H) curve has been studied in 0.2% carbon steel and 2.25Cr-1Mo steel under different tempered conditions. This study shows that the micromagnetic parameters can be used to identify the four stages of deformation, namely (i) perfectly elastic, (ii) microplastic yielding, (iii) macroyielding and (iv) progressive plastic deformation. However, it is observed that the MBE profile shows more distinct changes at different stages of tensile deformation than the hysteresis curve. It has been established that the beginning of microplastic yielding and macroyielding can be identified from the MBE profile which is not possible from the stress-strain plot. The onset of microplastic yielding can be identified from the decrease in the MBE peak height. The macroyielding can be identified from the merging of the initially present two-peak MBE profile into a single central peak with relatively higher peak height and narrow profile width. The difference between the Variation of MBE and hysteresis curve parameters with strain beyond macroyielding indicates the difference in the deformation state of the surface and bulk of the sample. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.