The relation between AC permeability and dislocation density and grain size in pure iron

Abstract

Magnetic properties of an iron-based steel derived from its major hysteresis loop are very sensitive to its microstruc- tures and have been, therefore, used for nondestructive evaluation (NDE) of degradation in infrastructure made by ferromagnetic materials. The permeability obtained from small ac field excitation may be a more useful parameter for NDE of ferromagnetic materials than one obtained from a major hysteresis loop from the viewpoints of electricity consumption and real-time measure- ments. In this paper a relation between ac permeability, calculated from impedance of coil elements, and dislocation density or grain size of pure iron were clarified. A potential of NDE using ac permeability is also discussed.