Tensile properties of 6061-T6 friction stir welds and constitutive modelling in transverse and longitudinal orientations

Abstract

Tensile stress–strain properties of Al alloy 6061-T6 (AA6061-T6) and its butt welds produced by the friction stir welding (FSW) process were characterized in two different loading orientations. AA6061-T6 FS welds were made under three sets of welding conditions. Micro-hardness tests were performed to investigate microstructural evolution during the FSW process. Flat tensile specimens were machined normal and parallel to the weld line. Transvers and longitudinal tensile tests were run on the base material (AA6061-T6) and its FS welds in an Instron testing machine. The strength and ductility (or fracture strain) of the FS welds observed in the transverse orientation were substantially less than those in the longitudinal orientation. Constitutive modelling of uniaxial tensile stress–strain behaviour in both orientations was presented using a rate-independent Ludwik equation. In addition, microstructures of the base material and its FS welds were examined with optical and transmission electron microscopy to discuss the decrease in the flow stress level and the increase in the strain hardening rate of the FS welds.

Keywords:

• Aluminium alloy 6016-T6
• constitutive modelling
• friction stir weld
• Ludwik equation
• microstructure
• TEM
• tensile orientation
• tensile properties

Acknowledgements

We would also like to express our appreciation to Professor JODAI Eiichi of Okayama University of Science for his assistance with the TEM imaging of the microstructure of the base material and joints.

Notes

Selected from Journal of Light Metal Welding 2015 53(8) 307–315.