Solute Diffusion Controlled Dendritic Growth Under High Undercooling Conditions

Liquid Cu₇₀Co₃₀ alloy is undercooled up to 363 K (0.22T_L) by using glass-fluxing technique. The LKT/BCT dendritic growth theory is modified and made applicable to predict the kinetic characteristics of dendritic growth in those alloy systems which have extremely curved liquidus and solidus lines. Actual calculations reveal that the dendritic growth of primary α-Co phase in Cu₇₀Co₃₀ alloy is constantly controlled by solute diffusion. The growth velocity of α-Co dendrite has a maximum value of 54.5mm/s at an undercooling of 333K. The calculated solubility of Cu in α-Co dendrite decreases with the increase of undercooling, which agrees well with the experimental data. Prior to peritectic transformation, the growth of α-Co dendrite is close to equilibrium solidification.