Tailoring microstructure in sintered Cu-Cr-Nb-Zr alloys for fusion components

High temperature, creep resistant heat sink materials represent a critical need for plasma facing components in future fusion reactors. In this study, we employ direct current sintering (often referred to as spark plasma sintering) to produce a Cu-Cr-Nb-Zr (CCNZ) alloy from gas-atomized feedstock powder with tailored precipitate distributions for enhanced stability and creep resistance. Microstructure was characterized by synchrotron X-ray diffraction, small angle X-ray scattering, and electron microscopy techniques. We report a multi-modal precipitate distribution containing submicron Cr (similar to 493 nm) and Cr2Nb (similar to 90 nm) precipitates at grain boundaries and a high density of nanoscale Cr (similar to 8 nm) precipitates homogeneously distributed through the Cu matrix. By comparing the as-sintered and aged microstructures, precipitation kinetics are discussed in the context of dislocation networks due to the high sintering pressures biasing precipitate formation and the role of subsequent recovery and recrystallization. Due to the presence of the multi-modal precipitate distribution, the sintered CCNZ alloy exhibited a high hardness of 133.2 HV while retaining an appreciable thermal conductivity of 298.4 W/m.K and electrical conductivity of 74.6% relative to the International Annealed Copper Standard. (C) 2021 Elsevier B.V. All rights reserved.