Silicon impact on carbon ordering at the martensite lattice: molecular dynamics simulations

Abstract

Despite their widespread use in the industry, silicon-alloyed bainitic steels remain understudied in many respects. There is no available in-formation on the impact of silicon impurities on the properties of martensitic structure; this article deals with this issue. We present the results of computer simulation of the impact of silicon impurities on tetragonal distortion of martensite lattice and the interaction of carbon atoms in the body-centered cubic (bcc) lattice of iron using the molecular dynamics method. We developed interatomic potentials that make it possible to describe the interactions of Fe-Si-C in martensite within the framework of the embedded atom model (EAM). It has been established that when silicon is added to steel, the lattice constant c decreases noticeably and the constant a increases slightly. The tetragonality expressed by c/a ratio decreases with respect to the results of the G.V. Kurdumov experiment for any carbon concentrations. The impact of silicon on the formation of martensite was studied through calculation by minimizing the energy of the strain-induced interaction parameter from the order-disorder transition theory in Zener-Khachaturyan interstitial solutions, which determines the critical temperature of the bcc-bct (body-centered tetragonal) transition. We have not confirmed the direct proportional dependence of the change in the tetragonality of martensite and the nature of carbon activity variation during alloying with silicon, which increases activity but decreases tetragonality.