CHARACTERIZATION OF PURE IRON AND (130-PPM) CARBON-IRON BINARY ALLOY BY BARKHAUSEN NOISE MEASUREMENTS - STUDY OF THE INFLUENCE OF STRESS AND MICROSTRUCTURE

The aim of this work is to measure and characterize the ferromagnetic noise from high purity iron and 130 p.p.m. carbon-iron alloy in variou s physical and metallurgical conditions. This is the basis of an indus trial development of Barkhausen noise as a non-destructive evaluation technique of microstructural changes. The amplitudes and shapes of Bar khausen signals are correlated with the grain size in pure iron and wi th the presence of interstitial carbon atoms in the iron matrix (magne tic after effect phenomena) in 130 p.p.m. carbon-iron alloy. This tech nique is also very sensitive to the location (inter- or intragranular precipitations), the nature (cementite or epsilon carbide), the densit y and size (coalescence effect) of carbide precipitates and internal s tresses. The influence of microstructure is analyzed in terms of Bloch wail interactions with crystal defects as pinning points, closure dom ains or dislocation configurations. (C) 1998 Acta Metallurgica Inc. Pu blished by Elsevier Science Ltd. All rights reserved.