Simulation and measurement of a vertical Bridgman growth system for β-NiAI crystal

A coordinated theoretical and experimental study of the temperature distribution inside a customized vertical Bridgman system for growing β-NiAl crystal has been conducted. The theoretical model accounts for the combined effects of phase change dynamics, the coupled heat transfer processes of conduction, convection and radiation, variable material properties, and complex geometry pertaining to the system. Comparisons between numerical predictions and experimental measurements show satisfactory agreement. The accuracy of the melting temperature of NiAl with stoichiometric composition, along with important processing parameters such as interface curvatures and temperature gradients across the interface, have been discussed in detail. Also assessed are possibilities of improving the solidification process, including coating the ampoule outer wall with a material of high radiative emissivity or decreasing the ampoule wall thickness.