The model of austenite structure state taking into account fluctuations of magnetic nature

Abstract

The results of magnetic state simulation of carbon steel austenite are presented in this work. Quantitative parameters of the areas of short-range magnetic order, which are presented in paramagnetic austenite matrix and are observed as potential places of α-phase nucleation, are examined. This austenite heterogeneity in steels and clean iron is confirmed by the experimental data; however, detailed quantitative study meets technical complication of such experiments. It is suggested to use the Ising model for realization of the calculation experiment. The obtained spin configurations were analyzed for determination of geometric parameters of magnetic inhomogeneities and period of their sustainable existence. Calculations were conducted within the temperature range of austenite phase existence in steel, as well as without and with taking into account presence of external magnetic field, which strengthens existing austenite heterogeneity and has the effect on conduction of phase transformations in steel. The results of simulation confirm presence of the areas of short-range magnetic order in austenite, their size is close to the existing theoretical assessments and experimental data. It is shown that temperature rise leads to decrease of dimensions, number and life period of clusters, but these parameters are still important at the temperature of martensite transformation in steel. Overlapping of external magnetic field creates the conditions for existence of large-size ferromagnetic clusters also at more high temperatures, as well as increases time of their sustainable existence. The external magnetic field provides the conditions for more intensive and multiplicative nucleation of ferromagnetic phase, similar to short-range magnetic order fluctuations in location of atoms during liquid metal cooling.