PNNL

Abstract

Two Cu-Cr-Nb alloys with Cr-to-Nb atomic ratio of 2 were manufactured from vacuum induction melting, melt spinning, consolidation, brazing, and baking. Microstructural characterizations using transmission electron microscopy and X-ray diffraction identified the cubic C15 Laves-phase Cr2Nb as the dominant precipitate in both alloys, which was cross-validated by thermodynamic calculations and atomistic simulations-based density functional theory (DFT). Besides cubic C15 Cr2Nb, hexagonal C14-phase Cr2Nb and a-BiF3 cubic structured Cr3¬Nb were also observed in the alloys, including a coherent interface formed between the Cr3Nb precipitate and the Cu matrix. The hardness of the alloys increases, and the electrical conductivity decreases with increasing alloying addition content; the trends were described by two practical equations. Further DFT simulations revealed that the electrical conductivity (conductance) of the Cu/Cr2Nb interface is an order magnitude higher than the intrinsic Cu high-angle grain boundaries.