Cu–Ni–Al合金圧延材の組織と機械的特性に及ぼす時効、仕上圧延および最終焼鈍の影響

抄録

Precipitation–strengthened Cu alloys are used as spring sheet materials for electronic components because of their high strength and electrical conductivity. Recently, rolled Cu–Ni–Al alloys with strengths comparable to those of Cu–Ti alloys have been developed and expected to become a new high–strength materials. Cu–Ni–Al alloys are manufactured through the integrated processes consisted of aging, rolling, and final annealing. Three processes are considered： precipitation strengthening of the γ’ phase during aging, work–hardening by rolling accompanied by softening due to a decrease in the ordering degree of the γ’ phase, and strength improvement due to the recovery of the ordering degree of the γ’ phase by annealing. However, the details have not yet been elucidated. Therefore, this study attempts to clarify the effects of aging, rolling, and final annealing on mechanical properties of Cu–Ni–Al alloys. At lower aging temperatures, continuous precipitation of the γ’ phase predominantly occurs in the matrix phase grains. Conversely, at higher aging temperatures and longer aging times, discontinuous precipitation of the γ’ phase at grain boundaries increases. Although the reduction in the ordering degree of the γ’ phase during rolling is larger when its particle size is smaller, the recovery of ordering degree by final annealing is larger. As a result, the recovery of hardness also tends to be larger. This suggests that the fine precipitation of the γ’ phase is important for strength improvement from the viewpoint of controlling properties by the ordering degree of the γ’ phase.