Cu-Ni-Si合金是近年來最受矚目的析出強化型銅合金，因其同時擁有優異的機械強度和導電性而廣泛應用於各種電子零件材料，例如電子彈簧、開關、導線框架等。許多文獻指出:不同元素的添加和熱機製程的改善可以更進一步提升Cu-Ni-Si合金的導電性和強度，以取代有毒的Cu-Be合金。
本研究為闡明部分Ni被Co取代的影響，共設計三款不同Co/Ni比例的Cu-Ni(-Co)-Si合金:Cu-8Ni-4Si、Cu-6Ni-2Co-4Si和Cu-4Ni-4Co-4Si，經由電弧熔煉、固溶熱處理、冷滾軋和時效處理，以XRD、OM、SEM和TEM觀察各階段的微結構並測量室溫下導電率、硬度和拉伸強度。實驗結果顯示Co含量越高導電性也隨之增高，而硬度由高至低排列則是為:Cu-6Ni-2Co-4Si、Cu-8Ni-4Si、Cu-4Ni-4Co-4Si。經由以上結果和微結構觀察，我們可以推斷出2%的Co添加量最為合適，因其有最高的強度表現，和次高的導電性。造成此結果的原因為溶質固溶度在高溫與低溫間的差異會隨著Co添加量上升而增大，同時比較固溶後的二次相的面積分率，我們發現當Co添加量超過2%時二次相(樹枝間晶和針狀析出物)大量增加，微硬度測試顯示這些二次相無法提供強度，並且使得基地相溶質純度降低，後續時效能產生的奈米析出物強化相也減少，所以2%Co是最佳添加量。導電性主要取決於基地相的Cu純度，而Co比起Ni在Cu的固溶度更低，所以導電性會隨著Co的添加量上升而上升。

Cu-Ni-Si alloys become the popular precipitation-hardening copper alloys recently. They are widely used for electrical applications such as electrical connectors, electrical springs and lead frames because of their high strength and high electrical conductivity. In order to substitute toxic Cu-Be alloys, many studies have suggested that the addition of other alloy elements and improvement of thermomechanical process can increase strength and electrical conductivity of Cu-Ni-Si alloys.
The present report investigates the effect of Co replacing part of Ni atoms. We designed three kinds of Cu-Ni(-Co)-Si with different Co/Ni ratios: Cu-8Ni-4Si, Cu-6Ni-2Co-4Si, and Cu-4Ni-4Co-4Si. The samples after arc melting, solution heat treatment, cold rolling and aging process were conducted microstructure analysis and then examined the hardness, tensile strength and electrical conductivity. The experimental results show that the electrical conductivity increases with the increasing amount of Co addition. As for the hardness and tensile strength, listed from highest to lowest are Cu-6Ni-2Co-4Si、Cu-8Ni-4Si、Cu-4Ni-4Co-4Si.

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