First-principles modeling of complexions at the phase boundaries in Ti-doped WC-Co cemented carbides at finite temperatures

WC-Co cemented carbides have a unique combination of high hardness and good toughness, making them ideal as tool materials in applications such metal machining or rock drilling. Dopants are commonly added to retard grain growth thereby creating harder material. Thin films with cubic structure been observed experimentally at phase boundaries between hexagonal WC fcc Co-rich binder when doping with, e.g., Ti, V, Cr. These generally considered play crucial role the inhibition effect. Therefore, thermodynamics these thin is important understand. Here, we construct, using ab initio calculations modeling, an interfacial diagram for Ti-doped WC-Co. We consider $\mathrm{C}\ensuremath{\leftrightarrow}\mathrm{vacancy}$ $\mathrm{W}\ensuremath{\leftrightarrow}\mathrm{Ti}$ substitutions by constructing alloy cluster expansions use Monte Carlo simulations calculate configurational free energy. Furthermore, force-constant fitting used extract harmonic energy ground-state structures. Additionally, information from thermodynamic databases couple our atomic-scale overall compositions typical materials. predict that Ti segregates WC/Co form two metallic layer thickness, both solid-state liquid-phase sintering temperatures. stable also low concentrations no Ti-containing carbide precipitates show essentially only inner film leaving almost pure W towards Co, ordering which has recent experimental high-resolution transmission electron microscopy studies.