Achieving high-strength metallurgical bonding between A356 aluminum and copper through compound casting

Aina Opsal Bakke,Yanjun Li,Lars Arnberg

doi:10.1016/j.msea.2021.140979

Aina Opsal Bakke, Yanjun Li + Show 1 more

Open Access

https://doi.org/10.1016/j.msea.2021.140979

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Abstract

Due to stable surface oxides on the solid copper surface and the ease of forming Al 2 O 3 films at the aluminum melt surface, it is difficult to achieve high-strength metallurgical bonding between the two materials through compound casting. In this research, a novel surface coating method for the copper inserts, namely hot-dip Sn-coating, has been applied. Through this method, a high-quality bond between a cast aluminum alloy A356 and commercially pure copper was achieved through a gravity compound casting process. Tensile tests showed that a maximum ultimate tensile strength (UTS) of 90.8 MPa could be obtained for the bimetal interface. Microstructures formed in the aluminum/copper interface were studied by optical- and scanning electron microscopy, while a sessile drop wetting test was used to study the wettability between the aluminum melt and Sn-coated copper substrates. The effects of Sn-coating on the wettability and the formation of interfacial microstructure were discussed. • Continuous metallurgical bond was achieved in aluminum/copper compound castings. • Sn-coating of copper significantly improved wetting between aluminum and copper. • Ultimate tensile strength of 90.8 MPa was measured for the Al/Cu castings. • Effect of the Sn coating layer was discussed.

Highlights

Bimetallic Al/Cu components can combine the high thermal and electrical conductivity of copper and the lightweight and good corrosion properties of aluminum
Pan et al reported a tensile strength of 88 MPa in the center of a friction welded Al//Cu joint where the intermetallic layer was 0.8 μm thick [13], while Asemabadi, Sedighi and Honarpisheh measured a tensile strength of 227 MPa in an explosively welded Al//Cu joint where no intermetallic phases were detected [14]
Two intermetallic phases in addition to the copper substrate and bright pure Sn have formed in the coating layer

Summary

Introduction

Bimetallic Al/Cu components can combine the high thermal and electrical conductivity of copper and the lightweight and good corrosion properties of aluminum Such components are used in bus bars, yoke coils and armored cables, to name a few applications [1,2,3,4]. As Cu and Al have a high affinity towards each other, especially at temperatures exceeding 120◦C, brittle intermetallic phases can form when joining the two materials [10,11]. This reduces the overall bonding strength of the component. Copper is first cast into the mold and as the copper solidifies, aluminum is cast onto it [20]

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