摘要
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 through atomistic simulations with a highly accurate machine learning interatomic potential.In the single crystal MPEA,we find 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.
基金
This work is funded by the office of Naval Research under Grant number N00014-18-1-2392
The authors also acknowledge computational resources provided by the Triton Shared Computing Cluster(TSCC)at the University of California,San Diego and the Extreme Science and Engineering Discovery Environment(XSEDE)supported by National Science Foundation under grant no.ACI-1053575.
