Heat Flux Transients and Casting Surface Macro-Profile During Downward Solidification of Al-12% Si Alloy Against Chills

Abstract

Heat flux transients were estimated during downward solidification of Al-12% Si alloy (A413) against aluminum and graphite chills. The thermal plot of graphite chill indicated one-dimensional heat flow in the initial stages which then changes to two-dimensional heat transfer. The heat transfer becomes one-dimensional again during the final stages of solidification. In aluminum chill, heat flow was nearly one-dimensional. Experiments were designed to verify whether the peak heat flux is an artifact of the experiment. The results clearly showed that the occurrence of the peak in the heat flux transients is not an artifact of the inverse model or the experimental technique. The macro-profile of the casting surface in contact with the chill revealed the occurrence of crests and troughs. A mechanism based on the convection within the liquid metal below the solid shell was proposed to account for the formation of wavy casting surface.