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Effects of Grain Boundary Characteristics of Steel on Magnetoacoustic Emission Spectra

Published online by Cambridge University Press:  21 February 2011

M. Namkung
Affiliation:
NASA Langley Research Center, Hampton, VA 23665
W. T. Yost
Affiliation:
NASA Langley Research Center, Hampton, VA 23665
D. Utrata
Affiliation:
Association of American Railroads, 3140 S. Federal St., Chicago, IL 60616
J. L. Grainger
Affiliation:
AS&M Inc., 107 Research Dr., Hampton, VA 23666
P. W. Kushnick
Affiliation:
PRC Kentron Inc., 303 Butler Farm Rd., Hampton, VA 23666
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Abstract

The pulse height distribution of a magnetoacoustic emission (MAE) spectrum is expected to be generally Gaussian due to its random nature. The functional form of distribution depends on the microstructure of a ferromagnet since the domain wall-lattice defect interaction produces MAE. The present study investigated the effects of grain boundary characteristics on the properties of MAE spectra obtained by external AC magnetic field-driven domain wall motions. The results show the enhancement of domain wall-defect interaction as more grain boundary disorder is introduced to HY80 steel samples. This was confirmed by the growth of a non-Gaussian-like distribution in the tail section of histograms with increased population of impurities trapped at the grain boundaries causing embrittlement. It is found that the enhancement of domain wall-defect interaction, which is responsible for generation of high amplitude MAE pulses, also tends to reduce the rate of such MAE events by limiting domain wall motions. Application of a stronger AC magnetic field should increase the count rate of high amplitude MAE signals in more embrittled samples.

Type
Research Article
Copyright
Copyright © Materials Research Society 1989

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References

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