Toward physical modeling of laser welding: thermophysics revisited

Experimental determination of the thermophysical properties conductivity, viscosity, and surface tension of lithium iodide was carried out in the temperature range starting slightly above the melting point and up to about 950~K. These measurements are motivated by the search for a transparent substance, the Prandtl number Pr of which approaches or is even less than unity, and which shows a stable Marangoni effect with respect to a potential pollution of the melt. Such a combination of material properties is mandatory in the attempt of a physical modelling of laser welding processes where optical access to the bulk of the fluid is needed in order to measure the flow field. In an extension to these basic studies, also the electrical conductivity and the influence of the admixture of other iodides on Pr was studied exemplarily.