Microstructural characterisation and mechanical properties of dissimilar AA5083-copper joints produced by friction stir welding

Gihad Karrar,Alexander Galloway,Athanasios Toumpis,Hongjun Li,Fadi Al-Badour

doi:10.1016/j.jmrt.2020.08.073

Abstract

This work aims to study the influence of the tool rotational speed and tool traverse speed on dissimilar friction stir butt welds on 3 mm thick AA5083 to commercially pure copper plates. Complex microstructures were formed in the thermo-mechanically affected zone, in which a vortex-like pattern and lamellar structures were found. Several intermetallic compounds were identified in this region, such as Al2Cu, Al4Cu9 and these developed an inhomogeneous hardness distribution. The highest ultimate tensile strength of 203 MPa and joint efficiency of 94.8% were achieved at 1400 rpm tool rotational speed and 120 mm/min traverse speed. Placing the softer material (aluminium) on the advancing side produced an excellent metallurgical bond with no requirement for tool offsetting.

Highlights

Dissimilar aluminium/copper joints are commonly used where there are advantages in partially replacing the copper with aluminium for certain engineering applications such as electrical connectors, tubes of heat exchangers, transformer’s foil conductors and capacitor foil windings [1,2,3,4]
They claimed that friction stir welding (FSW) of aluminium to copper was difficult due to the formation of brittle intermetallic compounds (IMCs) which led to poor mechanical properties
When the rotational speed varied from 1000 to 1400 rpm and the traverse speed was in the range of 80–120 mm/min, visually acceptable welds with no surface defects were obtained at the following specific parameter sets:

Summary

Introduction

Dissimilar aluminium/copper joints are commonly used where there are advantages in partially replacing the copper with aluminium for certain engineering applications such as electrical connectors, tubes of heat exchangers, transformer’s foil conductors and capacitor foil windings [1,2,3,4]. They claimed that FSW of aluminium to copper was difficult due to the formation of brittle intermetallic compounds (IMCs) which led to poor mechanical properties In their studies [18], the dissimilar mechanically mixed zone i.e. stir zone and thermo-mechanically affected zone (TMAZ) exhibited a complex microstructure with several IMCs such as Al2Cu, CuAl and Al4Cu9. Noticeable improvements in the ultimate tensile strength (UTS) were observed when the IMC thickness increased, especially at the interface between the aluminium base metal and the stir zone Their findings [20] were in agreement with other studies [21,22,23,24], whereas other published work [25,26] proposed that the joint mechanical strength depended on the volume fraction, geometry and distribution of the IMCs

Objectives

Results

Conclusion