Abstract
Effects of Be content and heat–treatment conditions on development of heterogeneous–nano structure and mechanical properties of Cu–Be alloys were systematically examined. With increasing Be concentration from 0.4 to 2.14 in mass%, volume fraction of “eye”–shaped twin domains developed in the 90% cold–rolled samples increased up to 4.9%. In addition, the volume fraction further increased to 7.1% when Co was excluded although Be concentration was 1.86 mass%. Therefore, increase in Be content promotes mechanical twinning, in contrast, precipitates appear to impede it. Still more, it was revealed that excess Be was consumed for formation of γ– and β–phases in the Cu–Be alloy with 2.14 mass% Be. Age hardenability at 588 K was more significant with increasing Be content, even while increment in tensile strength was not substantial. And these tendencies were more emphasized when solution treated at higher temperatures and for longer period of time. The highest tensile strength achieved was 1.7 GPa of the Cu–Be alloy with 2.14 mass% Be when tested along transverse direction, which is slightly higher than 1.5 GPa when tested along rolling direction. The above experiments indicated important role of age hardenability as well as the volume fraction of “eye”–shaped twin domains.
