Dependences of magnetic Barkhausen emission and magnetoacoustic emission on the microstructure of pearlitic steel

• Published in: Philosophical magazine (Abingdon, England) England), 2004-06, Vol.84 (18), p.1821-1839
• Main Authors: Lo, C. C. H., Scruby, C. B., Smith, G. D. W.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Magnetic properties and materials; Magnetization curves, hysteresis, Barkhausen and related effects; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Physics
• ISSN: 1478-6435; 1478-6443
• DOI: 10.1080/14786430410001663196

The relationships between microstructure, mechanical behaviour and magnetic properties of completely pearlitic steels have been investigated, with the objective of determining the applicability of magnetic measurements to non-destructive evaluation of the properties of high-strength pearlitic steels. High-carbon steels were heat treated to produce completely pearlitic structures with various interlamellar spacings, and their magnetic properties, including hysteresis loops, Barkhausen emission (BE) and magnetoacoustic emission (MAE) profiles, were measured. MAE profiles were found to have two peaks at the knee of hysteresis loop, while BE profiles show only a single peak at about the coercive field for all samples. The peak height ratio of the MAE profiles and the amplitude of the BE profiles increase monotonically with increasing pearlite spacing, whereas coercivity is inversely proportional to pearlite spacing. These results can be interpreted in the context of magnetic domain structures and magnetization reversal processes observed by Lorentz transmission electron microscopy, which revealed that, in specimens with smaller pearlite spacing, reverse domains nucleated and grew at higher reverse magnetic field, and domain wall jumps across cementite lamellae were smaller than in samples with coarser pearlites. The good correlation observed between the magnetic properties, mechanical strength and microstructures of these steels provides the basis for rapid and effective non-destructive assessment of their properties for industrial applications.