Abstract
The effect of the Ni/Si mass ratio and combined thermomechanical treatment on the microstructure and properties of ternary Cu-Ni-Si alloys is discussed systematically. The Cu-Ni-Si alloy with a Ni/Si mass ratio of 4–5 showed good comprehensive properties. Precipitates with disc-like shapes were confirmed as the Ni2Si phase with orthorhombic structure through transmission electron microscopy, high-resolution transmission electron microscopy, and 3D atom probe characterization. After the appropriate thermomechanical treatment, the studied alloy with a Ni/Si mass ratio of 4.2 exhibited excellent mechanical properties: a hardness of 290 HV, tensile strength of 855 MPa, yield strength of 782 MPa, and elongation of 4.5%. Compared with other approaches, the thermomechanical treatment increased the hardness and strength without sacrificing electrical conductivity. Theoretical calculations indicated that the high strength was primarily attributed to the Orowan precipitation strengthening and secondarily ascribed to the work hardening, which were highly consistent with the experimental results. The appropriate Ni/Si mass ratio with a low content of Ni and Si atoms shows high strength and excellent electrical conductivity through combined thermomechanical treatment. This work provides a guideline for the design and preparation of multicomponent Cu-Ni-Si-X alloys with ultrahigh strength and excellent electrical conductivity.
Highlights
Cu-Ni-Si system alloys have wide electrical applications, such as in circuits, connectors, and lead frames, where high mechanical properties combined with excellent electric conductivity and thermal conductivity are required [1,2]
Studies on Cu-Ni-Si system alloys have mainly focused on three aspects: first is the effect of Ni/Si ratio on the microstructure and properties of Cu-Ni-Si alloys, second is the different heat treatments for alloys that were explored to enhance their physical properties, and the last is the addition of microelements to Cu-Ni-Si alloys to synthesize a new multi-element alloy with optimal comprehensive
For the different Ni/Si mass ratios of alloys, the hardness shows the same tendency in the whole time period, and the peak aging is generally achieved under the aging condition of 500 ◦ C for 2 h
Summary
Cu-Ni-Si system alloys have wide electrical applications, such as in circuits, connectors, and lead frames, where high mechanical properties combined with excellent electric conductivity and thermal conductivity are required [1,2]. In the last decades, outstanding comprehensive properties have been achieved for age-hardening alloys. This accomplishment contributes to the detailed understanding of the uniform distribution of nano-scale Ni-Si precipitates and helps in determining the properties of the matrix. Some alloys with low Ni and Si content, such as KLF-1, C70250, and C70350, have favorable electrical conductivity (>45% IACS) and are used for high-density miniaturized electronic components. Studies on Cu-Ni-Si system alloys have mainly focused on three aspects: first is the effect of Ni/Si ratio on the microstructure and properties of Cu-Ni-Si alloys, second is the different heat treatments for alloys that were explored to enhance their physical properties, and the last is the addition of microelements to Cu-Ni-Si alloys to synthesize a new multi-element alloy with optimal comprehensive
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