Effect of annealing on the structure and properties formation of a copper alloy alloyed with palladium and silver

A copper alloy with small additions of palladium and silver (Cu–1.5Pd–3Ag (at. %))—which has potential applications as a corrosionresistant conductor of weak electrical signals—was studied using X-ray diffraction analysis, microhardness measurements, specific electrical resistivity, and tensile mechanical properties tests. Samples were examined in several initial states: quenched (from 700 °C) and deformed at room and cryogenic temperatures (with a 90 % reduction in cross-sectional area in both cases). To study the processes of structural reorganization and property evolution, the initial samples were annealed in the temperature range from 150 to 450 °C (in 50 °C increments), followed by cooling in water or air. The duration of the heat treatments ranged from 1 to 48 hours. It was established that annealing the Cu–1.5Pd–3Ag alloy at temperatures below 450 °C leads to the precipitation of silver-based phase particles in the Cu matrix. Annealing of the initially quenched alloy was found to slightly increase its specific electrical resistivity (ρ) from 3.55·10–8 to 3.8·10–8 Ohm·m (after 48 h at 250 °C). It was revealed that alloying copper with 1.5 at. % palladium and 3 at. % silver enhances the strength properties (the yield strength of the alloy reaches 500 MPa) and raises the recrystallization temperature, while the electrical conductivity of the alloy remains around 50 % IACS. The optimal combination of properties (strength, ductility, and electrical conductivity) is observed after annealing the pre-cryodeformed alloy at 250 °C for less than 18 h. Extending the annealing time causes overaging, resulting in softening. The results of this study can be applied in the development of a new high-strength material with reduced electrical resistivity.

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