Atomistic simulation of processes in Ni-base alloys with account for local relaxations

Ordering in Ni-base superalloys is the crucial process controlling the development of the characteristic two-phase microstructure and subsequently the mechanical properties. Systems containing up to six alloying elements typical of advanced Ni-based superalloys are modelled in this work using a Monte Carlo approach with phenomenological Lennard-Jones pair potentials and interactions up to the third coordination sphere. Three-dimensional crystal block is used with over 105 atoms. Molecular dynamics approach is used to relax local atomic positions in course of ordering processes under applied stress. The importance of taking into account both relaxation of modelled block dimensions and relaxation of local atomic positions is discussed.