Heterostructure and multiple nano-phases achieve superior strength-ductility-conductivity synergy of laser additive manufacturing copper alloy

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.