Изменение свойств железа при ОЦК-ГЦК-фазовом переходе

Abstract

Using the previously developed method for calculating crystal properties based on the Mie–Lennard-Jones pair potential, the thermodynamic properties of the BCC and FCC phases of iron at the temperature of the polymorphic BCC-FCC phase transition are calculated. 23 properties of iron and their changes during the BCC-FCC transition are calculated. Calculations have shown that properties such as the Gruneisen parameter, the coefficient of thermal expansion, and the heat capacity practically do not change during the BCC-FCC transition. The elastic modulus, specific entropy, Poisson's ratio, and specific surface energy change in the same way as the molar volume, i.e. within 1%. The Debye temperature and its pressure derivative decrease at the BCC-FCC transition in the same way as the distance between the centers of the nearest atoms increases, i.e. within 2-3%. Based on the analysis of experimental data known from the literature, it is shown that even relatively accurately measured parameters such as the coefficient of thermal expansion and elastic modulus are measured with an error exceeding the values of jumps in these parameters at the BCC-FCC transition. It is indicated that amorphization or nanostructuring of a certain portion of iron during the BCC-FCC transition can contribute to changes in the properties of iron during this phase transition.