Dendrite growth kinetics of βZr phase within highly undercooled liquid Zr−Si hypoeutectic alloys under electrostatic levitation condition

The liquid Zr_100-xSi_x (x = 1, 3, and 5) alloys were substantially undercooled by up to 392 K (0.19T_L), 423 K (0.21T_L), and 451 K (0.23T_L), respectively, under the electrostatic levitation condition. The measured dendrite growth velocity of the primary βZr phase increased with the enhancement of liquid undercooling. Although the undercooling ability showed an increasing tendency with the increase in the Si content, dendrite growth was obviously depressed due to the dominance of solute diffusion controlled growth. Their critical undercoolings for kinetics transition from solute diffusion to thermal diffusion controlled growth were determined. It demonstrates a remarkable refinement of dendrites and an increasing trend of Si solubility in αZr dendrites with increasing undercooling.