Complex, Multiphase Behaviour in the Ti \(_x\) NbMoTaW and Ti \(_x\) VNbMoTaW Refractory High-Entropy Alloys

We study the influence of Ti additions on the predicted atomic arrangements and microstructure of the NbMoTaW and VNbMoTaW refractory high-entropy alloys. The addition of Ti is understood experimentally to improve the room-temperature ductility of these alloys, but also to lead to the emergence of chemical inhomogeneities during processing. Our modelling suggests that the addition of Ti leads to competition between phase segregation and phase ordering in these systems, and also to increased ordering temperatures when compared to the systems with no Ti present. Lattice-based Monte Carlo simulations evidence competing interactions and complex, multiphase behaviour in the Ti-containing systems. These results give fundamental physical insight into the experimentally observed microstructure of these systems, and serve as further validation of our modelling approach.