Dendrite growth in solidification of undercooled Co₈₀Pd₂₀ alloy

Much interest has been focused on the dendrite growth of undercooled melts in the theoretical field of solidification research. The BCT model was widely accepted to interpret dendrite growth behavior in rapid solidification process. In present case, substantial undercooling ΔT up to 415 K was achieved for Co₈₀Pd₂₀ melt applying molten glass denucleation combined with cyclic superheating. The dendritic morphology of the experimental alloy was investigated by OM and the solute concentration of appointed micro-area was analyzed by EDS. Based on the BCT dendrite growth model, the theoretical calculation of the related parameters of the dendrite growth process included tip radius R, dendrite growth velocity V, solute concentration in liquid at dendrite tip C_L^* and undercooling contributions were completed. It can be found that the dendritic morphology was only formed in the undercooling ranges of 0-72 K and 95-142 K. With the initial undercooling increasing, V rises steeply due to the increase of the growth driving force, but R displays a complicated variation attributed to the combine effects of thermal/solute diffusion. EDS analysis reveals that the experimental data of C_L^* is in accordance with the theoretical predication by BCT model. The results confirmed that the dendrite growth in undercooled Co₈₀Pd₂₀ melts can be interpreted successfully by BCT model.