5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Thermal diffusivity and individual solutal diffusivity of component play a significant role during natural convection dominated solidification of multicomponent alloys. In this study, in situ experimental observations of solidification of a ternary salt solution (water-potassium nitrate-ammonium chloride) are reported. The phase diagram of the ternary salt solution consists of three distinct regimes, distinguished based on the mode of heat transfer through the liquids. Each regime is divided into two subregimes on the basis of the primary solidifying component. In Regime II, the cotectic solidification leads to conduction dominated heat transfer through the liquid. The present study shows the real-time evolution of the convective flow in Regime II with different primary solidifying elements (ammonium chloride or potassium nitrate) using in situ optical techniques. A bottom-cooled experiment was performed using Mach-Zehnder interferometer (for thermal/solutal transportation) and particle image velocimetry (for flow field) in a rectangular cavity. The experiments show that the sub-regime II (with ammonium chloride as the primary phase) leads to the formation of double-diffusive convecting layers whereas the sub-regime-II leads to a more complicated convective flow with potassium nitrate as the primary solid. Furthermore, the mechanism of double diffusive convection in ternary mixtures is hypothesized.