Effect of Processing Conditions on Short-Range Order and Mechanical Properties of the NbMoTaW Multi-Principal Element Alloy

Refractory multi-principal element alloys (RMPEAs) are promising candidates for high-temperature applications due to their exceptional mechanical properties. In this work, we investigate the effect of processing conditions on the observed short-range order (SRO) in the NbMoTaW RMPEA, and the consequent effect on mechanical properties, using Monte Carlo/ molecular dynamics (MC/MD) simulations with a highly accurate machine learning interatomic potential. We demonstrate that SRO is maximized at an intermediate temperature range of 800K--1000K. A higher SRO results in higher stacking fault energies (SFEs), anti-phase boundary energies (APBEs), and critical resolved shear stresses (CRSS). We also show that Nb segregation in polycrystalline NbTaMoW is also present at intermediate annealing temperatures, and this Nb segregation can have the effect of retarding grain growth even at high temperatures.