Effect of shoulder cavity and welding parameters on friction stir welding of thin copper sheets

Abstract

The aim of this investigation was to study the influence of shoulder cavity and welding parameters on torque, defect formation, microstructure and mechanical properties of friction stir welds in very thin sheets of deoxidised copper. Three types of tools were used: a flat shoulder tool and two tools with conical shoulder cavities of 3 and 6° respectively. The welding parameters analysed were tool rotation and traverse speeds. It was observed that the torque, the microstructure and hardness and the formation of defects in the welds are influenced mainly by tool rotation speed and, to a lesser extent, by the traverse speed and shoulder cavity. The tensile properties of welds carried out at high rotation speeds are little affected by the shoulder cavity.

Keywords:

• FSW
• Tool shoulder cavity
• Copper alloys
• Thin sheets

The authors are indebted to the Portuguese Foundation for the Science and Technology through COMPETE program from QREN and to FEDER for the financial support and to company Thyssen Portugal–Aços e Serviços Lda for providing materials and heat treatments for the tools designed and fabricated in the project.