X-ray imaging of complex flow patterns during tungsten inert gas welding

Fusion welding techniques such as tungsten inert gas (TIG) welding process have been widely used in industrial and construction applications. The molten metal flow in the weld pool has a major impact on the microstructure evolution, chemical element distribution and defects formation during solidification, which subsequently determines the performance of the welds. However, limited real-time experimental data availability of internal flow behavior has been considered as a major barrier to achieve a thorough understanding and development of accurate weld pool prediction models. In situ x-ray imaging with the tracking particles facilitated us to visualize the flow evolution during the solid–liquid–solid transformation. Experimental results indicated the flow patterns are progressively becoming complicated with the expansion of the melt pool. The shape of the melt pool also changed according to this flow evolution. Our analysis of flow patterns concerning the underlying variation of the driving forces suggests that gravity-derived buoyancy has a considerable effect on determining fluid flow at the melt pool periphery compared to other regions.