Loop travel-path of fibre laser welded Alclad AA2219-O alloy

A loop or circular travel-path of fibre laser beam on Alclad AA2219-O aluminum alloy plates was investigated by varying laser penetration depths (partial and deep penetrations). Lap joint configuration was employed for the welding process. The mechanical properties and microstructures of the resultant welds were examined. The fracture morphologies of the welds subjected to axial loading were critically examined via scanning electron microscope (SEM). The result shows that loop or circular beam travel-path improves the lap shear failure load of full penetrated welds. The presence of Alclad on the surface of the alloy and penetration depth influence porosity formation in all welds. The fusion regions of welds are predominantly composed of equiaxed grain structures. The returning laser beam reduces the hardness of the start/end (S/E) fusion region and increases porosity level of the region as compared to the travel-path (TP) fusion region. Macro-pores (351-575 μm) significantly influence fracture pattern of welds whereas micro-pores (50-200 μm) show no obvious influence on the examined fracture surfaces. The fracture morphologies of partial and full penetrated welds are interfacial ductile shearing/fracture (across the adjoining fusion width) and porosity induced fracture (emanating from the start/end fusion region) respectively.