The influence of deformation at cryogenic or room temperature followed by annealing on the structure and properties of copper and its Cu–3Pd and Cu–3Pd–3Ag (at. %) alloys

Abstract

Due to low electrical resistivity, the Cu–Pd and Cu–Pd–Ag system alloys can be used as corrosion-resistant conductors of weak electrical signals. The paper deals with a comparison of the structure and physical-mechanical properties of Cu, Cu–3Pd and Cu–3Pd–3Ag (at. %) alloys after deformation at room or cryogenic temperature followed by annealing. The authors studied specimens in different initial states: quenched, deformed at room and cryogenic temperatures. To study the processes of structure rearrangement and the evolution of properties, annealing was carried out in the temperature range from 100 to 450 °C, followed by cooling in water. The duration of heat treatments was 1 h. The dependences of the yield strength and elongation to failure on the annealing temperature showed that cryodeformation significantly increases the thermal stability of the structure of both pure copper and the Cu–3Pd–3Ag ternary alloy. According to the temperature dependence of specific electrical resistivity of the deformed Cu–3Pd–3Ag alloy during heating at a rate of 120 deg./h, it was found that the decrease in electrical resistance caused by recrystallization begins at above 300 °C. The dependences of specific electrical resistivity on true strain showed that the structure rearrangement mechanisms during deformation are different for pure copper and the Cu–3Pd–3Ag alloy. The results of mathematical processing of the peaks in the diffraction patterns established that two phases appear in the Cu–3Pd–3Ag alloy after cryodeformation and annealing, one of which is silver-enriched, and the other is depleted. The study showed that during annealing of the deformed (especially after cryodeformation) Cu–3Pd–3Ag alloy, an anomalous increase in strength properties is observed. It was identified that alloying copper with palladium and silver leads to an increase in the recrystallization temperature. Thus, copper alloys with small palladium and silver additives are obviously attractive for practical applications, since they have improved strength properties, satisfactory electrical conductivity, and a higher recrystallization temperature compared to pure copper.