The role of the post-heat treatment on the Cr-based precipitates and related room temperature mechanical properties of the sintered Nb-lean Cu–Cr–Nb alloy

Abstract

Nb-lean Cu–Cr–Nb alloys have been widely applied in electrical industries as the structural conductive material owing to their excellent combination of the mechanical and electrical properties at room temperature. In this work, the influence of temperature during fast sintering and post-heat treatment strategies on the precipitate evolution and room temperature mechanical properties of the Cu–3Cr-0.5Nb (wt.%) alloy was investigated. The increasing sintering temperature will improve the density and mechanical properties of the alloy without any obvious grain growth during this non-equilibrium process, while the post-aging at lower and higher temperatures can effectively control the formation and coarsening process of the Cr-based precipitates. Systematic characterization was then conducted on the microstructural evolution, especially the altering precipitates’ size and distribution, in the alloy at both as-sintered and the aged conditions, which is correlated to its room temperature tensile properties. Lower aging temperature will induce the nucleation of the new Cr2Nb precipitates without causing a significant coarsening of the existing precipitates like aging at higher temperature. Therefore, the low-temp. aged sample exhibits the highest tensile strength and elongation due to the enhanced Orowan strengthening mechanism induced by its unique precipitate microstructure.