Experimental and Numerical Analysis of Microstructure and High-Temperature Tensile Behavior of a Directionally Solidified Superalloy

A comprehensive cellular automaton algorithm coupled with finite element method was developed for the simulation of temperature field, heat transfer characteristics and the anisotropic grain growth during a directional solidification (DS) process. Nucleation parameters at the interface of the alloy and the chill plate were adjusted at four levels, and the evolution of macrostructure during competitive growth of grains has been characterized. The sensitivity of grain structure to heat transfer coefficients between alloy/chill plate and alloy/ceramic mold was also evaluated at a constant nucleation condition. The results were compared with the microscopic images and measurements of the experimentally cast DS specimens. This model was then utilized for the development of another micro-mechanical finite element model of the cast bars including the realistic grain boundaries and misorientations. To complete a simulation of a whole manufacturing chain from casting process to mechanical behavior evaluation, high-temperature tensile behavior of the cast bars was then elucidated through experiment and FE analysis.