Phase-field microstructure-based effective thermal conductivity calculations in tungsten

Using a phase-field approach with the heat conduction equation, we predict the grain growth behaviors in tungsten (W) and their effects on effective thermal conductivity. Results show that the simulated grain growth kinetics is basically consistent with experimental observations. An empirical correlation is derived, describing the averaged grain area as a function of temperature and time. Further, we study the effect of grain growth, columnar crystal structure, and recrystallization on the effective thermal conductivity of W. It is found that the effective thermal conductivity increases nonlinearly with increasing grain size, and a simple correlation of converting two-dimension into three-dimension effective thermal conductivity is obtained. Interestingly, the effective thermal conductivity of the columnar crystal is relatively high along the elongated direction and higher than that of the isometric crystal. Nevertheless, the effective thermal conductivity decreases with the occurrence of the recrystallization due to the increased grain boundary density. Our results reveal that grain growth and grain structure can affect the capacity of heat transfer at high temperatures, which could be considered in the transient event of the long-time service of W materials in fusion devices.