Non-destructive evaluation of spheroidized steel using magnetoacoustic and Barkhausen emission

Magnetoacoustic emission (MAE) and Barkhausen emission (BE) measurements have been made on pearlitic steel samples annealed to produce spheroidized microstructures with various sizes and distributions of carbides. It was found that spheroidization of the pearlitic structure and coarsening of carbide particles result in a decrease in the peak height ratio of the MAE profile and the formation of a second peak in the BE profile. These results can be interpreted from observations of the domain structure by Lorentz microscopy. The sensitivity of the MAE and BE profiles to the carbide size and morphology makes both techniques useful for monitoring the microstructure of spheroidized steels