Increase in strength and electrical conductivity of cu - 0.8% hf alloy after rotational forging and subsequent aging

The structure, electrical conductivity and mechanical properties (including fatigue strength) of the Cu - 0.8% Hf alloy after rotational forging (RF) at various degrees of deformation and subsequent aging have been studied. It is shown that RF leads to the formation of a microstructure that is elongated in the direction of deformation. With an increase in the degree of deformation, the average grain width decreases, and the grains become more and more elongated. After RF at ε = 2.77, the formation of an ultrafine-grained structure with an average subgrain size of 173±12 nm is observed inside the elongated grains. With an increase in the degree of deformation, the strength of the alloy increases with a decrease in ductility. Subsequent aging causes an increase in the strength of the hardened alloy and the alloy after RF at ε = 0.58 and ε = 1.39; there is no hardening after RF at ε = 2.77. In all cases, aging increases electrical conductivity of the alloy as a result of the decomposition of the supersaturated solid solution and the separation of the Cu5Hf phase. The best combination of mechanical and functional properties was obtained after RF at ε = 2.77 and subsequent aging at 475 °C for 2 h: ultimate strength 461±28 MPa, ductility 12.5±2.4%, fatigue limit 325 MPa, electrical conductivity 90.4±1.9% IACS.