The effect of BCC-Cu precipitation on magnetism in thermally aged Fe-1wt. % Cu model alloys

Magnetic properties of thermally aged Fe-1wt.%Cu alloys were investigated. With increasing aging time, coercive force gradually increased and Barkhausen signal peak voltage decreased. Both behaviors suggested that Bloch wall movement was hindered by Cu precipitates and the pinning was strengthened with increasing precipitate size. On the other hand, at the initial precipitation stage where the precipitate size is much smaller than the Bloch wall width, the inclination of the hysteresis curve greatly changed, but recovered with further thermal aging. The peculiar inclination behavior would be associated with the nucleation of coherent bcc-Cu precipitates. Index Terms--Anisotropy, Barkhausen noise (BHN), coercive force, hysteresis curve, nondestructive evaluation (NDE), precipitation, thermal aging.