| Abstract Scope |
Compositionally complex ultra-high temperature ceramics, such as transition metal carbides, may have improved or tuneable properties such as hardness, ductility, and oxidation resistance. In such multi-principal component systems, configurational entropy effects are thought to overcome any opposing enthalpic effects inhibiting mixing, resulting in single solid solution phases. However, despite the individual transition metal carbides having similar properties and behaviour on an atomic or electronic scale, the elemental differences in multicomponent materials results in complex local behaviour that depends on the local atomic environment. This can result in complex multi-phase mixtures with short- and long-range ordering, affected by the composition and temperature of the system. This work uses modelling approaches including density functional theory (DFT) calculations and CALPHAD (phase diagram) modelling to explore order-disorder transitions within the MC1-x (M=Ti,Zr,Hf,Nb,Ta) composition space spanned by these systems, including variations in number and ratio of transition metal elements as well as carbon vacancy concentration. |