Solute interaction effects on grain boundary segregation in ternary alloys

Abstract In polycrystalline materials, the segregation of elements to grain boundaries (GBs) can be harmful, e.g., embrittling the GB, or helpful, e.g., strengthening the GB or stabilizing nanocrystalline states, depending on the alloying elements present. While the GB segregation tendency in binary alloys can be reasonably estimated, the effect of additional elements on this equilibrium remains largely speculative, making it difficult to design the GB chemistry of ternary alloys. Using a lattice-model framework and Monte Carlo simulations, we develop a first-order theoretical framework with which the GB segregation behavior in ternary alloys can be estimated based on the thermodynamic properties of the constituent binary systems. We then experimentally study GB segregation in the Pt-Au-Pd system as a case study. In line with our predictions, this system exhibits induced co-segregation of Pd to GBs at 400 °C, driven by the presence of Au.