Complex Strengthening Mechanisms in Multi-Principal Element Alloys, aka High-Entropy Alloys

Xiangguo’s excellent paper on “Complex strengthening mechanisms in the NbMoTaW multi-principal element alloy” has just been published on npj Computational Materials. Refractory multi-principal element alloys (MPEAs) have exceptional mechanical properties, including high strength-to-weight ratio and fracture toughness, at high temperatures. Here we elucidate the complex interplay between segregation, short-range order, and strengthening in the NbMoTaW MPEA using a machine learning interatomic potential. We show that the single crystal MPEA exhibit greatly reduced anisotropy in the critically resolved shear stress between screw and edge dislocations compared to the elemental metals. In the polycrystalline MPEA, we demonstrate that thermodynamically driven Nb segregation to the grain boundaries (GBs) and W enrichment within the grains intensifies the observed short-range order (SRO). The increased GB stability due to Nb enrichment reduces the von Mises strain, resulting in higher strength than a random solid solution MPEA. These results highlight the need to simultaneously tune GB composition and bulk SRO to tailor the mechanical properties of MPEAs.

Check out this work at this link.