Macroscale modelling of Bridgman furnace solidification for the prediction of texture evolution and columnar to equiaxed transition

Abstract

Bridgman furnaces are commonly used in solidification research owing to their convenience when setting the desired solidification parameters, specifically, the nominal temperature gradient and nominal growth rate. The work outlined here describes the development of two macroscopic models for the prediction of texture evolution in Bridgman furnace experiments that use cylindrical shaped samples. The first model employs a 1-dimensional axisymmetric thermal model (suitable for small sample diameters) with columnar mush front tracking; equiaxed growth is analytically modelled using the Avrami’s extended volume concept. The second model employs a 2-dimensional axisymmetric thermal model (suitable for small and large sample diameters), also with columnar mush front tracking; in this model an indirect method of columnar to equiaxed transition prediction (Equiaxed Index) is employed. Both models have been developed as part of the European Space Agency research projects: GRADECET (Gravity Dependence of Columnar to Equiaxed Transition in Gamma Ti˗Al Alloys) and CETSOL (Columnar to Equiaxed Transition in Solidification Processing), for the purposes model validation and enlightenment of planned future experiments.