Investigations on the material flow and the role of the resulting hooks on the mechanical behaviour of dissimilar friction stir welded Al2024-T3 to Ti-6Al-4V overlap joints

During friction stir lap joint welding, hooks are systematically formed at the interface of dissimilar Al2024/Ti-6Al-4V plates. Various dimensions and shapes observed according to welding parameters (welding speed, rotational speed double-pass). Based on digital image correlation (DIC) during tensile shear tests, it is found that features govern fracture behaviours and, hence, mechanical properties overall welds. In particular, three obtained: interface, in Al2024 across Ti-6Al-4V plate, which was never reported Al/Ti studies. The aims this work (i) study influence FSW mechanisms formation (ii) understand role both AS RS behaviour welds, by means two new approaches. First, investigated X-ray tomography provided some innovative insight into material flow (3D viewing). these qualitative quantitative results, used as tracers scenarios generation proposed. Then, contribution stress distribution clearly revealed calculations stresses reached around hooks. Contrary hook, hook sharp top characterized a concentration. results showed greatly influenced size microstructural defects inside Ti-6Al-4V, depend parameters. conclusions, relationship between achievable parameters, resulting behaviours. addition, based understanding flow, another proposed optimize properties.