Achieving high strength and high conductivity synergy through hierarchical precipitation stimulated structural heterogeneities in a Cu-Ag-Zr alloy
Xiang Wu, Jiaxuan Zhang, Richu Wang, Zainab Zafar, Xiaochun Liu, Yujing Liu, Lihua Qian, Lixin Sun
Abstract
Cu alloys can be plastically deformed to reach ultra-high strength, but often at an expense of their electrical conductivity. Here we report that the introduction of hierarchical precipitations and the resultant microstructural heterogeneities at different scales could overcome the strength-conductivity tradeoff in Cu-Ag-Zr alloy. The intrinsic particle size dependent precipitation behavior, owing to the different cooling rate during powder atomization, has been inherited after hot isostatic pressing (HIP) of powders into bulk sample. The following cold rolling and aging created multi-scale structures with the sub-micron particles at grain boundaries and sub-micron-to-nano scale precipitates in the grain interior. Those introduced heterogeneous precipitate configurations also altered the evolution of deformation structures during cold rolling and aging, with partially recrystallized grains embedded in highly deformed matrix featured by high density of dislocation and substructures, which results in an excellent combination of tensile strength (704 MPa), electrical conductivity (88.7% IACS), and tensile elongation (14.9%). Besides, no significant coarsening in the micro-nano structures is observed after annealing at 450 °C for 1 h. The findings in this work proposed a novel approach for designing high-strength, high-conductivity, and high-thermal stability copper alloys based on hierarchical precipitation-stimulated structures at nano-to-micron scale.