Finite-difference - cellular automaton modeling of the evolution of interface morphology during alloy solidification under geometrical constraint: Application to metal matrix composite solidification.

摘要

Solidification processing plays an essential role in dictating the properties of both infiltrated as well as dispersion-cast metal-matrix composites (MMCs). Furthermore, performance requirements may necessitate selective reinforcement of an alloy component using specifically designed reinforcement architecture. Not only is the solidification of an alloy through such an architecture a major contributor to the final properties of the component, but it is also important in the context of understanding and optimizing the overall infiltration/casting process. As these advanced applications of solidification technology emerge, it becomes apparent that conventional solidification theory may not be adequate for the development and optimization of the requisite techniques.; This work was intended to establish the feasibility for using a cellular-automaton growth model for the simulation of the evolution of interface morphology during binary alloy solidification. The motivation for such an endeavor is derived from the need to understand and predict the development of solidification structures within components of complex geometry, as in the case of liquid-state processed MMCs.; A two-dimensional cellular-automaton was coupled with a finite-difference calculation for solute diffusion. Alloy solidification was simulated over a range of experimental conditions. The model was shown to predict growth mode transitions, thermal and solutal interfacial conditions, overall dendritic structure, and microsegregation. The model was also checked against analytical solutions for one-dimensional growth. Finally the model was applied to various systems exhibiting geometric constraint. Simulations were evaluated with respect to the effects of the constraint on the interface morphology as well as solutal and thermal conditions at the growth front. Many simulated interactions compared favorably with experimental observations. For these reasons, despite various limitations which were identified, this modeling approach appears to have significant potential for application in the field of MMC solidification as well as other areas where the effects of constrained thermal and solutal fields become significant.