Investigation of phase transformation mechanism of Fe-Cr, Ni-Cr, Fe-Ni and FeCrNi alloy systems by molecular dynamics method

In the presented study, Fe-Cr, Ni-Cr, Fe-Ni and Fe-Cr-Ni binary and ternary alloy systems, which are classified as medium entropy alloys, were modelled by using molecular dynamics (MD) simulation method based on SCIGRESS multiplatform molecular design, modeling and dynamics software. Model systems were built at specific concentration ratios in accordance with the crystal lattice structures in the phase diagrams. Firstly, the potential energy function based on the Grujicic-Zhou (GZ) type embedded atom method was chosen as the potential function suitable for the systems. Then, the model systems were subjected to the relaxation process for a determined period of time and the most stable structures in the phase space were obtained. Finally, the phase transformation mechanisms of the model systems were investigated by applying heating-cooling processes on the most stable structures. In these processes, thermodynamic parameters such as temperature, volume, enthalpy, potential energy and density were calculated. In addition, the phase transformation mechanism and structural properties were analysed using radial distribution functions (RDF) and mean square displacements (MSD). Three-dimensional pictures of MD cells and the number of crystal structures were obtained using the visualization and analysis software by using the atomic positions obtained during the transformations. In all these processes, the results obtained by the MD calculation method were interpreted and compared with the experimental data.