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<p>Dissimilar joining of aluminum (Al) to copper (Cu) is essential for emerging lightweight electrical and thermal systems, yet its performance is critically limited by the rapid formation of brittle intermetallic compounds (IMCs) at the Al/Cu interface. This work investigates the effectiveness of an electroless nickel (Ni) coating in suppressing IMC growth during arc joining of Al to Cu. Gas tungsten arc (GTA) welding with tailored heat input was used to selectively melt Al while keeping Cu solid, producing a solid–liquid interface characteristic of a brazing-type reaction. In uncoated direct joints, Cu readily dissolved into molten Al, generating a graded sequence of reaction products: an <i>in situ</i> interfacial IMC layer, followed during cooling by hypereutectic Al<sub>2</sub>Cu, eutectic <i>α</i>-Al/Al<sub>2</sub>Cu, and hypoeutectic regions. The formation of coarse hypereutectic Al<sub>2</sub>Cu was identified as the primary factor degrading joint strength, directly linked to the high Cu dissolution rate. Introducing a ~ 10&#xa0;<i>μ</i>m electroless Ni coating markedly reduced Cu dissolution owing to the low solubility and diffusivity of Ni in al. This suppression decreased the Al<sub>2</sub>Cu layer thickness by more than 70 pct, effectively reducing the interfacial brittle flaw size that governs crack initiation and propagation. Consequently, the Ni-assisted joints exhibited more than a 50 pct increase in tensile strength and a ~ 20 pct improvement in elongation compared to the direct Al/Cu joints. These findings demonstrate that electroless Ni coating offer an effective and scalable strategy for controlling intermetallic evolution and enhancing the structural integrity of Al–Cu dissimilar arc joints.</p>

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Ni-Assisted Arc Joining of Al–Cu Dissimilar Metals: Intermetallic Control to Enhance Mechanical Performance

  • 期刊论文

  • 发表日期：

    2026年4月17日

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  • Vahid Pagard,
  • Alireza Pirjamadi,
  • Majid Pouranvari

摘要

Dissimilar joining of aluminum (Al) to copper (Cu) is essential for emerging lightweight electrical and thermal systems, yet its performance is critically limited by the rapid formation of brittle intermetallic compounds (IMCs) at the Al/Cu interface. This work investigates the effectiveness of an electroless nickel (Ni) coating in suppressing IMC growth during arc joining of Al to Cu. Gas tungsten arc (GTA) welding with tailored heat input was used to selectively melt Al while keeping Cu solid, producing a solid–liquid interface characteristic of a brazing-type reaction. In uncoated direct joints, Cu readily dissolved into molten Al, generating a graded sequence of reaction products: an in situ interfacial IMC layer, followed during cooling by hypereutectic Al2Cu, eutectic α-Al/Al2Cu, and hypoeutectic regions. The formation of coarse hypereutectic Al2Cu was identified as the primary factor degrading joint strength, directly linked to the high Cu dissolution rate. Introducing a ~ 10 μm electroless Ni coating markedly reduced Cu dissolution owing to the low solubility and diffusivity of Ni in al. This suppression decreased the Al2Cu layer thickness by more than 70 pct, effectively reducing the interfacial brittle flaw size that governs crack initiation and propagation. Consequently, the Ni-assisted joints exhibited more than a 50 pct increase in tensile strength and a ~ 20 pct improvement in elongation compared to the direct Al/Cu joints. These findings demonstrate that electroless Ni coating offer an effective and scalable strategy for controlling intermetallic evolution and enhancing the structural integrity of Al–Cu dissimilar arc joints.