Global and local mechanical properties and microstructure of Bobbin tool friction-stir-welded Al–Li alloy

Abstract

AA2198–T851 sheets were welded by bobbin tool friction stir welding using a rotational speed of 800 rpm and welding speed of 42 mm min⁻¹. The microstructure and precipitates within the joint were characterised by transmission electron microscopy. The global and local mechanical behaviour was determined using a digital image correlation system. Specific attention was given to the relationship between the local microstructure and properties across the joint, which govern the global strength and ductility of the welds. A lower global elongation of the joint is caused by the premature strain localisation in the softened zone.

Keywords:

• Friction stir welding
• Bobbin tool
• Microstructure
• Mechanical properties
• Strain localisation

Acknowledgements

Feifan Wang would like to acknowledge the China Scholarship Council (No. 201306290117) for the financial support. This work has been carried out under the auspices of the Cooperation Agreement between the School of Material Sciences and Engineering of the Northwestern Polytechnical University and the Helmholtz-Zentrum Geesthacht (HZG 161/2014 and 111 Project/B08040).