静电悬浮条件下液态锆的热物理性质与快速枝晶生长

The thermophysical properties and dendritic growth kinetics of undercooled liquid zirconium were investigated by electrostatic levitation method. The results show that the hypercooling limit and specific heat of liquid zirconium are determined to be 524 K(0.25T_m) and 41.03 J/(mol∙K), respectively, according to the relationship between undercooling and solidification plateau time. Meanwhile, the measured density, viscosity and surface tension of molten zirconium display a linear increase with the decrease of temperature. The hemispherical total emissivity of liquid zirconium is derived from the thermal equilibrium equation, which exhibits an increase tendency within the temperature range of 1752-2315 K. Besides, the dendritic growth velocity is experimentally measured by using a high speed camera according to the in-situ observation of S/L interface migration during recalescence, which agrees well with the theoretical prediction of LKT/BCT rapid dendritic growth model. The dendritic growth velocity shows a power increase relationship with undercooling, which reaches 48 m/s at the maximum undercooling of 376 K(0.18T_m). In addition, the Vickers microhardness of rapidly solidified pure zirconium is derived as an increase tendency with enhanced undercooling.