Abstract: Nanoscale silver (Ag) and copper (Cu) particles have garnered significant attention as potential low-temperature sintering interconnects due to their small-size effects and exceptional physical properties. Compared to pure metals, alloys can have many advantages including reduced melting points, enhanced strength, and cost-effectiveness. This study successfully used the spark ablation method to form metastable nanoscale Ag-Cu supersaturated solid solution particles (28 at.% Cu) with a narrow size distribution (average diameter: 19.5 nm), uniform morphology, and remarkable oxidation resistance (60-day ambient air stability). Under optimized sintering conditions (260 °C, 2 MPa, 30 min), the sintered Ag-Cu particles exhibited exceptional shear strength (60.74 MPa) and low resistivity (2.67 × 10^-7 Ω m), surpassing the values of pure Ag sintered counterparts under identical conditions. The enhanced performance originated from synergistic energy contributions during sintering. The lattice distortion energy of the supersaturated solid solution particles combined with the surface free energy externally supplied thermal activation, and a mechanical driving force promote atomic redistribution. Specifically, Cu atoms precipitated from the Ag matrix and diffused to the Ag grain boundaries, ultimately forming dispersed Cu grains that filled the sintered microstructures. Our method presents a novel green strategy for fabricating supersaturated solid solutions that pass the thermodynamic immiscibility limitations, while its environmentally benign synthesis method holds substantial implications for advancing sustainable development in the industry.

Key words: Spark ablation method, Metastable nanoscale Ag-Cu supersaturated solid solution, Lattice distortion energy