Modeling grain size and dislocation density effects on harmonics of the magnetic induction

Microstructural attributes of steels affect hysteretic magnetic properties because the microstructure affects domain wall movement and pinning. Two im portant features are grain size and dislocation density. The consensus expe rimentally is that the coercivity tends to be linearly related to the inver se of the average grain diameter and to the square root of the dislocation density. In this article, these experimental tendencies are utilized in for mulating the dependence of the hysteresis parameters of the Jiles-Atherton model as a function of grain size and dislocation density. The results are then used in computing the first and third harmonics of the magnetic induct ion as a function of grain size and dislocation density. This is done via a n adaptation of a hysteresis model formulated by Jiles for higher excitatio n frequencies. The results indicate that the harmonic amplitudes decrease m onotonically with inverse grain size and the square root of dislocation den sity. Since increasing inverse grain size and dislocation density are corre lated with increasing tensile strength, the results are consistent with exp erimental results for the decrease of the harmonic amplitudes with increasi ng tensile strength in automotive steels. Also, the harmonic amplitudes dec rease with increasing excitation frequency, consistent with experiment. (C) 2001 American Institute of Physics.