Modeling grain boundary and surface segregation in multicomponent high-entropy alloys

Grain boundary (GB) and surface segregation have been studied by computer simulations in the so-called Cantor alloy: Co20Ni20Cr20Fe20Mn20. Monte Carlo, molecular dynamics, as well as lattice statics methods, using second nearest-neighbor modified embedded atom method potentials, have been applied sequentially in order to equilibrate the alloy. Simulations of GB segregation showed that Cr segregates most strongly, and is accompanied by weak Mn segregation. In contrast, in the case of surface segregation, Mn segregates most strongly to the outermost surface atom plane. However, when adsorption is measured as the integrated excess of the components over a 4-atom-layer region adjacent to the surface, Cr again emerges as the dominant segregant. A mass balance model has also been applied to the results of the segregation behavior, in order to estimate the potential for depletion of the bulk alloy composition due to segregation at GBs. It is found that significant depletion of bulk composition can occur if the alloy grain size falls below about 100 nm.