Investigations of weld profiling and intermetallic formation in laser welding of steel-To-Aluminium: A multi-physics CFD approach using beam shaping

The mechanical properties of steel-to-aluminium laser welded joints are dependent on the interfacial intermetallic compounds (IMCs) and the weld interface area. Recent technological advances in laser beam shaping have shown improvements in keyhole stability, porosity formation, optimisation of weld profiles and reduced interfacial IMCs. This study investigated the effect of keyhole stability which is critical in the formation of IMCs and weld profiles. Multi-physics computational fluid dynamics (CFD) simulations and high-resolution microscopy were used to calibrate the model using various core/ring beam power ratios and study their effect on fluid-flow and microstructural evolution. The wider spot from the ring beam improved keyhole stability, whilst the narrower core beam created instability of the weld pool. This study revealed that the strength of the weld was improved by 16% with a ring-only versus core-only beam and total IMC thickness was reduced by up to 50%.