The measurement of dendrite tip propagation velocity during growth into undercooled metallic melts

High-speed digital imaging provides new insight into the development and evolution of solidification structures during recalescence from undercooled metallic melts. Rejection of the heat of fusion from the dendrite tip into the liquid results in local thermal gradients, which have been successfully imaged as growth progresses across the exposed surfaces. By tracking the steady-state propagation of this interface, bulk growth velocities may be evaluated and the morphology of the underlying dendritic array may be predicted. The implications of the measurements and analyses presented in this work support classical growth theory at undercoolings below the critical value of Delta T* approximate to 160 degrees C. Transient effects may also be quantified. At high undercoolings, the extent of negative deviation from growth theory is seen to be lower for material processed using a containerless levitation technique, Using a digital video technique, global macrostructural solidification behavior and the potential for interaction between individual dendrites within the array may be investigated.