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Balancing strength and ductility presents a significant challenge in the γ′ phase-strengthened Nickel-based superalloys fabricated by laser beam powder bed fusion. This study introduced stable multi-scale heterogeneous microstructure through heat treatment for the first time, which achieves an excellent strength-ductility synergy. The formation mechanism of heterogeneous microstructure during heat treatment and its correlation with mechanical properties are discussed in detail. The results show that the heat treatment leads to the formation of a multi-scale heterogeneous microstructure, including bimodal grains, nano-sized γ′ phases and twins, which activated several strengthening mechanisms, significantly enhancing strength. During the tensile process, stress-induced stacking faults, Lomer-Cottrell locks, and secondary twins activate multiple plastic deformation modes. This effectively improves the work-hardening capacity while maintaining good ductility. The heat treatment process designed in this study achieved a good balance between strength (yield strength: 1281 ± 8 MPa, ultimate tensile strength: 1609 ± 7 MPa) and ductility (16.6 ± 0.3%). These findings propose a new strategy for development of precipitation-strengthened superalloys.

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.