Age-Induced Precipitating and Strengthening Behaviors in a Cu-Ni-Al Alloy

Microstructural response and variations in strength and electrical conductivity of a Cu-20 at. pct Ni-6.7 at. pct Al alloy during isothermal aging at temperatures from 723 K to 1023 K (450 degrees C to 750 degrees C) were investigated to discuss the age-induced precipitation behavior and strengthening mechanism. At all aging temperatures, fine spherical gamma '-Ni3Al particles were found to nucleate coherently with parent Cu grains by continuous precipitation and then grew gradually by Ostwald ripening. Domains with a high density of twins developed at grain boundaries during aging below 873 K (600 degrees C) followed by cellular components composed of fiber-shaped gamma '-Ni3Al and Cu solid solution phases at the domain boundaries later. Both the domains and cellular components were suppressed at aging above 923 K (650 degrees C). The age-induced strengthening principally resulted from fine dispersion of gamma '-Ni3Al coherent particles in the grains. The precipitation strengthening by the fine gamma '-Ni3Al coherent particles exhibited a maximum at an aging temperature of 873 K (600 degrees C), resulting in excellent mechanical properties such as a high hardness of 340 +/- 7 HV and an ultimate tensile strength of 980 +/- 14 MPa, which are comparable to those of other commercial age-hardened Cu-Be, Cu-Ni-Si, and Cu-Ti alloys.

Automated summary

The study focused on the microstructural response and variations in strength and electrical conductivity of a Cu-20 at. pct Ni-6.7 at. pct Al alloy during isothermal aging at temperatures from 723 K to 1023 K (450 degrees C to 750 degrees C). It was found that the age-induced strengthening mainly resulted from fine dispersion of gamma'-Ni3Al coherent particles in the grains, exhibiting a maximum at an aging temperature of 873 K (600 degrees C). The fine precipitation strengthening by gamma'-Ni3Al coherent particles resulted in excellent mechanical properties, comparable to other commercial age-hardened Cu alloys.