Thermosolutal convection and macrosegregation during solidification of hypereutectic and hypoeutectic binary alloys in statically cast trapezoidal ingots

Thermosolutal convection patterns and evolution of macrosegregation during solidification of hypereutectic and hypoeutectic NH4CL-H2O binary systems in trapezoidal side-chilled ingots with negative and positive slopes have been numerically investigated. The results have been compared with the base case of solidification in a rectangular ingot. During solidification of NH4CL-70 pct H2O hypereutectic alloy, channels and “A segregates” develop early in the solidification process. When the slope is positive, channels penetrate to a larger distance inside the ingot. Whereas, for negative slope, they are shifted outward toward the chilled wall and are vertically oriented. During solidification of NH4CL10 pct-H2O hypoeutectic alloy, circulation cells which emerge in the narrow melt at later stages of the process are shown to be responsible for the development of V-shaped segregates in the final casting. The final degree of macrosegregation is higher for both positive and negative slopes of the ingot chilled wall compared to the rectangular ingot.