EFFECT OF COMPOSITION AND ANNEALING TEMPERATURE ON THE STRUCTURE AND PROPERTIES OF Cu–Ni ALLOYS PROCESSED BY SEVERE PLASTIC DEFORMATION

The structure of Cu–Ni alloys processed by high-pressure torsion (HPT) by 5 revolutions at room tem-perature and its thermal stability under subsequent annealing have been studied using transmission electron microscopy and microhardness measurements. The influence of three main factors on the structure and microhardness under deformation and annealing depending on the composition has been revealed: the changes in homologous temperature and stacking fault energies (SFE) and the effect of solid solution formation. The combination of these factors results in the non-monotonic change in the structure obtained by HPT (crystallite sizes and microhardness) and its thermal stability depending on the alloy composition. In copper-rich alloys, a decrease in the homologous temperature with an increase in Ni content plays a decisive role in the refinement of the structure, strengthening and thermal stability. When Ni is alloyed with Cu, the structure and its thermal stability do not change as significantly, since the increase in homologous temperature and the decrease in SFE compensate each other, but due to the effect of solid solution formation in alloys with a nearly equiatomic composition, the most dispersed and thermally stable structure is formed.