Magneto-acoustic and Barkhausen emission: Their dependence on dislocations in iron

Abstract

Abstract Magneto-acoustic emission (MAE) and Barkhausen emission (BE) have been measured from polycrystals of pure iron which had been strained by 4.9%. The specimens were then heat-treated at successively higher temperatures. The heat treatments resulted in stress recovery and, at higher temperatures, a reduction in the dislocation density. BE activity and MAE activity profiles were measured after each anneal as a function of the magnetizing field, and the number of Barkhausen events was counted as a function of their peak amplitude. At low fields the intensity of the BE and MAE activities shows a strong trend as a function of the annealing temperature, which is in agreement with the temperature dependence of the dislocation density. At higher fields there are additional fluctuations in the BE and MAE activities as a function of the annealing temperature which occur at temperatures below those of dislocation recovery. These results show that both MAE and BE are sensitive to the dislocation density, and that the techniques are potentially useful for non-destructive characterization of materials.