Phase diagram of the Cu-Ni3Al pseudo-binary system

Cu-Ni-Al alloys with a Ni to Al ratio of approximately 3.0 are of particular interest for the development of electrically conductive products; thus, investigating their phase behavior is essential for achieving specific properties in these materials. In this study, the phase diagram of the Cu-Ni3Al pseudo-binary system was experimentally determined using cast and fully heat-treated Cu-Ni3Al alloys with a wide range of compositions, via microstructural observation and different quantitative analyses. The Cu-Ni3Al system undergoes a eutectic reaction Liquid ? alpha-Cu solid solution (Cu-ss) with an FCC structure +gamma '-Ni3Al with an ordered FCC L1(2 )structure. As the combined Ni and Al (Ni3Al) content increased, the microstructure transitioned from a single alpha-Cuss phase to two eutectic phases (alpha-Cuss and gamma '-Ni3Al), to a primary gamma '-Ni3Al phase and two eutectic phases, and to a single gamma '-Ni3Al phase. The solidus and liquidus temperatures increased with the (Ni+Al) content. The solid solubility of (Ni+Al) in the alpha-Cuss phase (C(Ni+Al)) could be described by an Arrhenius-type equation (ln C(Ni+Al) = 5.50 - 2637/T), indicating a significant temperature dependence. In contrast, the solubility of Cu in the gamma '-Ni3Al phase did not significantly decrease with the temperature. The phase diagram of the Cu-Ni3Al system was constructed from these results. The phase diagram will be useful in the development of Cu-Ni-Al alloys with exceptional strength and electrical conductivity. (C) 2022 Elsevier B.V. All rights reserved.