| During the solidification of a binary alloy under off-eutectic conditions, solutal and thermal forces can produce imperfections in the form of solute-rich channels. Many researchers observe that the use of uni-directional solidification for alloys can provide increased resistance to creep and thermal fatigue in the final solidified ingot. Most experimental methods applied to date have been poorly suited to study the complex dynamic fields associated with these convective phenomena. In this work, the novel technique of Molecular Tagging Velocimetry was extended and applied to investigate the transient velocity fields present during the uni-directional solidification of a transparent alloy analog (ammonium chloride). The whole-field two-component velocity map near the mushy layer and above the chimney, where lighter fluid rises, was measured at different times during the solidification process and at different locations. The mushy region exhibits a maximum velocity of order 1mm/s in both components while the plumes have a maximum velocity of order 7mm/s in the upward component. The measured velocity fields are expected to enhance understanding of the diverse transport phenomena present during the solidification process and provide quantitative verification of future computational analysis. |
