Ni/Al比を変化させたCu–Ni–Al合金の強度特性

抄録

Cu–Ni–Al alloys are promising high–strength copper alloys for connector applications. In this study, we investigated the mechanical properties and microstructures of Cu–20Ni–6.7Al, Cu–16Ni–5.4Al, Cu–12Ni–5.4Al, and Cu–8Ni–5.4Al alloys (at.%) after aging to establish design guidelines for high–strength connectors. When the Al concentration was constant, increasing the Ni/Al ratio beyond 2.4 did not lead to an increase in the 0.2% proof stress. Conversely, when the Ni/Al ratio was kept constant, increasing the Ni and Al concentrations resulted in higher 0.2% proof stress. The variation in 0.2% proof stress among the specimens correlated with the amount of Ni_₃Al (L1_₂ structure) present. In all specimens, discontinuous precipitation occurred at grain boundaries from the early stages of aging. These results indicate that strength can be effectively controlled by adjusting the Ni and Al concentrations while maintaining a Ni/Al ratio close to 2.4. Furthermore, suppressing discontinuous precipitation may enhance bending formability and fatigue properties.