Abstract: The liquid Zr_100-xV_x (x = 8.6, 16.5, 30) alloys were undercooled to the maximum undercooling of 364 K (0.18 T_L), 405 K (0.21 T_L), and 375 K (0.21 T_L), respectively, by using electrostatic levitation technique. The Zr_91.4V_8.6 and Zr_83.5V_16.5 alloys present only one recalescence during liquid/solid phase transition, while the Zr₇₀V₃₀ alloy presents a transformation from two recalescence to one recalescence phenomenon with a critical undercooling of approximately 300 K. According to the LKT/BCT model, the calculated results of the primary β-Zr dendrite growth velocity in undercooled liquid Zr_91.4V_8.6 and Zr_83.5V_16.5 alloys agree well with the experiments. The velocity inflection points at 119 K of Zr_91.4V_8.6 alloy and 201 K of Zr_83.5V_16.5 alloy could be explained by the competition between solutal undercooling control and thermal undercooling control modes. For Zr₇₀V₃₀ alloy solidified in the P1 with twice recalescence, a critical second undercooling of 253 K and corresponding undercooling of 65 and 244 K are obtained. When the undercooling is in the range of 65-244 K, the second undercooling would be greater than 253 K, and the residual liquid phase would solidify into anomalous eutectic microstructure for Zr₇₀V₃₀ alloy. The Vickers hardness of Zr_100-xV_x (x = 8.6, 16.5, 30) alloys all show a quadratic relationship with undercooling. Under electrostatic levitation condition, the mechanical property of Zr-V alloys could be significantly regulated through solidifying the alloys at different undercoolings.

Key words: Undercooling, Zr-V alloy, Electrostatic levitation, Solidification, Hypoeutectic, Dendrite, Growth kinetics