Magnetization curves of plastically deformed Fe metals and alloys

The hysteresis loop of plastically deformed Fe metals and alloys was measur ed for single crystals, polycrystalline iron, and A533B steel samples, and the dislocation density and structure of these samples were observed by ele ctron microscopy. The relation between structure-sensitive properties and a pplied stress sigma was analyzed in connection with grain boundaries and di slocations. The coercive force H-c increases with sigma and is represented by one curve in all the samples. The magnetic susceptibility chi(c) above t he coercive field can be described by a simple relation to the magnetic fie ld H. chi(c)=c/H-3 in a limited region of H. The parameter c depends only o n lattice defects such as dislocations and the grain size and has a simple relation to them, but is independent of the kinds of samples or of the proc ess of plastic deformation. The susceptibility chi(c) is explained in compa rison with the susceptibility chi(r) in the range of approach to saturation . The magnetic properties c and H-c are discussed considering the dislocati on density and its distribution including the effect of grain boundaries. T hese magnetic properties are useful for nondestructive tests of metal fatig ue. (C) 2000 American Institute of Physics. [S0021-8979(00)01102-6].