Microstructure evolution of molten zirconium oxidative solidification: Experiment and numerical simulation

The high-temperature oxidation behavior of zirconium alloys is a major limitation to their high-temperature applications. The microstructural characteristics during the oxidative solidification process of molten zirconium significantly influence its oxidation kinetics. This study combines experimental and numerical simulation methods to investigate the microstructural evolution characteristics during the oxidative solidification of molten zirconium. High-temperature steam environment experiments are conducted to observe the morphology of oxidative solidification dendritic structures. A phase field model considering flow, heat transfer, and oxygen transport is developed. The model is verified using theoretical solutions and experimental results. Based on the developed model, simulation analyses of the oxidative solidification process of molten zirconium are conducted. The results indicate that the model can accurately simulate the growth of dendrites and the inhomogeneity of oxygen content during solidification. The influence of external macroscopic conditions on the microstructural characteristics of solidification is investigated. The results indicate that the oversaturation of the zirconium melt determines the driving force for oxidative solidification. Both excessively low and high oversaturation can form a relatively stable solid–liquid interface. Melt flow causes deviation of the oxidative solidification dendrites. As melt flow intensifies, the deviation angle of the dendrites gradually increases, and the width of the dendrites decreases.