Research on the characteristic scale and undercooling during directional solidification of single-phase alloy

A transparent model alloy, succinonitrile (SCN)-1.48%Salol (mass fraction), was directionally solidified at the constant velocity. The primary dendritic/cellular spacing, tip radius and tip temperature have been measured as a function of growth velocity. The critical velocity for planar interface instability was obtained. It is shown that with the increase of growth velocity, the primary spacing decreases to a local minimum value first, and then increases to a local maximum value, finally decreases again. The cell/dendrite transition happens when the primary spacing increases from the local minimum to maximum value. Experimental results were compared to BH-L and self-consistent models. It is found that the tip temperature predicted by BH-L model shows a large difference with the experimental results, but all experimental results agree with the self-consistent model.