Rapid dendritic growth kinetics of primary phase within supercooled Zr-V alloy at electrostatic levitation state

Abstract

The liquid Zr100−xVx (x = 8.6, 16.5, 30) alloys were undercooled to the maximum undercooling of 364 K (0.18 TL), 405 K (0.21 TL), and 375 K (0.21 TL), respectively, by using electrostatic levitation technique. The Zr91.4V8.6 and Zr83.5V16.5 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 Zr91.4V8.6 and Zr83.5V16.5 alloys agree well with the experiments. The velocity inflection points at 119 K of Zr91.4V8.6 alloy and 201 K of Zr83.5V16.5 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 Zr100−xVx (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.