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The heat resistance of copper alloys is desirable to improve while it services at high temperature as electrically and thermally conductive components. In present paper, the strengthening pattern of nickel-based superalloys is expected to be applied in copper alloys. Here the Cu50Ni37.5M12.5 (M = Al, Cr, Mo) alloys were prepared by vacuum arc melting and heat-treated in the corresponding conditions to obtain three different kinds of typical microstructure. The room temperature (RT) properties (hardness and resistivity) and high temperature properties (melting point, softening temperature and variable temperature resistivity) of the three alloys are contrasted and analyzed in detail. The Cu50Ni37.5Al12.5 alloy strengthened through the γ′ phase coherent precipitation shows the best conductivity and highest hardness (5.47 %IACS (International Annealed Copper Standard) and 310.1 HV). The splitting of the γ′ phase is contributing to hardening at high aging temperature. The resistivity-temperature behavior of the three alloys shows that the resistivity with rising temperature consists of the ideal lattice resistivity and the resistivity increment due to the defects. The Cu50Ni37.5Al12.5 alloy has the smallest room temperature resistivity and its resistivity maintains the lowest during the whole heating process (RT-1077K). Therefore, the coherent precipitated γ′ phase is expected to improve the heat resistance of the copper alloys while maintaining its electrical conductivity.

Enthalpic interaction between the elements determines the stability of the local structures in the alloy system. Multicomponent synergistic effect is expected to improve the thermal stability and the relevant properties by regulating the enthalpic interaction. In this work, the composition of Cu-Ni-Sn alloys is explained by introducing the cluster-plus-glue-atom mode, and the strong and weak enthalpic interaction elements Si and Zn, respectively, are chosen for multi-componentization of Cu-Ni-Sn alloys. The results demonstrate that the synergistic effect of Zn and Si improves the stability of both the Cu matrix and D022 or L12-γ′ phase, inhibits the discontinuous precipitation effectively and gains a notable higher strength-over-resistivity ratio (HR / ρR) than the Cu-15Ni-8Sn (wt. %) (C72900) alloy. After adding Si and Zn, the reinforcing enthalpic interaction between the elements is the crucial factor for the stability enhancement of the alloys, and it is embodied by two aspects: (a) the reducing elastic strain energy in the solution treated alloys; (b) the more homogeneous surface potential and the higher work function in the age treated alloys. Additionally, Compared with the Cu80Ni15Sn5 alloy that based on the ideal cluster formula, the Cu79.68Ni15.63Sn4.69 alloy, based on the modified cluster formula: {[Cu-CuxNi12-x]Cu3}a{[Sn-NiyCu12-y]Sn3}16-a, possesses a preferable thermal stability whatever solution treated or age treated state, and exhibits a decreasing amount of discontinuous precipitation although has a slightly lower HR / ρR, which is beneficial to the improvement of the workability of the alloys. The modified cluster formula is more suitable for the compositional design of Cu-Ni-Sn alloys. The work provides an effective theoretical and experimental basis for the composition design of high stability Cu-Ni-Sn alloys.