Effect of Ni Addition on the Interfacial Strength of Al/Cu Dissimilar Welds Produced by Friction Stir Lap Welding

Kota Kurabayashi,Shun Tokita,Yutaka S Sato

doi:10.3390/met12030453

Abstract

Al/Cu dissimilar joining is a key technology for reducing the weight and cost of electrical components. In this study, the dissimilar friction stir lap welding (FSLW) of a Ni-containing Al alloy to pure Cu was performed, and the effects of the addition of Ni on the weld strength and interfacial microstructure were examined. A thin intermetallic compound (IMC) layer was observed at the Al/Cu weld interface produced by FSLW. The addition of 3 at.% Ni effectively improved the weld strength, although the thickness of the IMC layer increased. The IMC layer formed at the Al/Cu interface without Ni comprised CuAl2 and Cu9Al4 from the pure Al side. In contrast, the IMC layer formed with 3 at.% Ni consisted of (Ni,Cu)Al, CuAl, and Cu9Al4 from the Al side. The addition of Ni eliminated the weak CuAl2/Cu9Al4 interface, thereby improving the weld strength. The results of this study suggest that the strength of the Al/Cu weld can be effectively improved by the thinning of the IMC layer caused by FSLW and the change in interfacial microstructure caused by Ni addition.

Highlights

Multi-material systems have attracted wide attention owing to their improved properties from combining dissimilar materials
This study showed that the addition of Ce to the Zn–22Al filler metal refined the interfacial microstructure and decreased the thickness of the intermetallic compound (IMC) layer formed in the Al/Cu brazed joint
Continuous IMC layer was observed at the Al/Cu dissimilar interface, which was thicker toward the weld center

Summary

Introduction

Multi-material systems have attracted wide attention owing to their improved properties from combining dissimilar materials. Many studies examined the mechanical properties, interfacial microstructure, and corrosion behavior of multi-material systems, such as Al/Fe structure [1–3]. The multi-material structures of Al and Cu have been widely researched in the field of welding engineering, thereby reducing the cost and weight of electrical components. Al–Cu intermetallic compounds (IMCs), such as CuAl2 , CuAl, and Cu9 Al4 , form at the Al/Cu dissimilar interface because of the high affinity between Al and Cu [4–8]. A significant degradation of the Al/Cu weld strength due to the formation of brittle IMCs during the welding process has been reported as a common problem in many studies [8–11]. Zhou et al [12] examined the relationship between the thickness of the IMC layer and the welding current (heat input) during pulsed double-electrode gas metal arc welding (DE-GMAW)–brazing of Al to Cu and concluded that the thickness of the IMC layer increased with an increase in the welding current over

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