Heterostructure and multiple nano-phases achieve superior strength-ductility-conductivity synergy of laser additive manufacturing copper alloy
Shupeng Ye, Zuming Liu, Xinyan Feng, Yazhou Zhang, Daoyan Jiang, Tao Liu, Runxing Zhou
Abstract
Synchronous improvement in strength, ductility and conductivity is a challenge for copper alloys. We propose introducing a heterostructure and multiple nano-phases into copper alloys to improve the comprehensive properties of Cu-Cr-Nb-(Y) alloys. The heterostructure, composed of non-uniformly distributed grains and dislocations, was formed by laser powder bed fusion. After rare earth Y microalloying, the heterostructure was enhanced and the Cr2Nb phases were refined. Direct-aging treatment promoted the precipitation of nano Cr phases, while Y and Nb elements accelerated the precipitation rate according to first-principles calculations. Heterostructure and the formation of multiple nano-phases, including 20–80 nm Cr2Nb and 2–5 nm Cr phases, synergistically enhance the strengthening effect and improve the conductivity. Overall, hetero-deformation-induced and precipitation strengthening are the most important strengthening mechanisms. The Cu-4.8Cr-2.2Nb-0.15Y alloy exhibited an ultimate tensile strength (UTS) of 885 ± 8 MPa, an elongation of 12.9 ± 1.1% and a conductivity of 46.4 ± 0.2% IACS after peak-aging. After over-aging, the UTS and conductivity exceeded 650 MPa and 60% IACS. This work provides a simple and effective approach for developing high-performance copper alloys.