Analysis of Microstructural Changes in Soft Magnetic Materials Based on Direct Evaluation of Magnetization Process Dynamics

A correlation between thermal aging and the dynamics of magnetization processes (especially domain wall motions) in standard steel sheet materials were studied. The response of magnetic quantities, e.g., the flux density and/or induced voltage, to artificial aging induced by annealing of the samples at 753 K for aging time t_a ranging from 0 to 60 h was investigated. Ring-shaped samples were magnetized with defined exciting field having special waveform shape allowing direct observation of transients associated with sudden change of waveform attributes (e.g., slope). The parameters of observed first-order exponential-like transient curves were demonstrated to be influenced by heat treatment of the samples. Obtained results allow the application of suggested procedure as a promising new method for nondestructive inspection of various ferromagnetic construction materials.