Microstructural evolution and local mechanical properties evolution throughout friction stir welds in Al 6005A

摘要

Friction stir welding experiments on a 6005A-T6 aluminium alloy were carried out using a fully instrumented milling machine. In particular, thermocouples were placed at various distances from the weld centreline. A campaign of tensile tests on specimens oriented transversely to the welding line showed that fracture almost always takes place on the retreating side of the weld. Some of these tensile tests were performed with digital image correlation to study the local deformations and their evolution. Microstructural characterisations were performed in different zones of the welds using transmission electron microscopy. Micro-tensile tests were also performed in the different zones parallel to the welds. The local tensile mechanical properties were compared with the micro-hardness and interpreted in terms of observed microstructures. It is shown that, the global properties of the welds result from a complex interaction between the local yield stress and local strain hardening capacity resulting from the specific thermal history and microstructure evolution undergone by each zone of the welds.