Modeling of Liquid Metal Infiltration of Porous Fiber Preform During Squeeze Casting

Abstract

The present work adopts a new approach to the analytical modeling of infiltration of porous fiber preforms by liquid metal in the squeeze casting of metal matrix composites, with the assumption that the process is adiabatic and that the flow is unidirectional. Fluid dynamics is described on the basis of Darcy's law, while separate equations are derived to explain the thermal behavior of the liquid metal and the fiber, assuming that the thermal interactions between the two are interfacial. Unlike earlier models, this approach does not consider the thermal behavior of a “composite,” but instead studies the behavior of the liquid metal and the fiber preform separately. In addition to the conventional application of heat balance techniques and development of partial differential equations involving temperatures, this work introduces supplementary conditions for temperature calculations, specifically at the entry and front points during infiltration. Differential equations are solved by a method of finite differences, and the problem of additional unknowns (preform temperature) at the infiltration front position is overcome using the “virtual point” concept. Simple expressions are derived for the calculation of process parameters like total time for complete infiltration and time for solidification, on the basis of which the occurrence of complete infiltration is predicted. A novel attempt in generating the profiles of the preform and liquid temperatures at specific instants during infiltration has also been made. The relative influence of the liquid superheat temperature, the preform preheat temperature, and the squeeze pressure on the infiltration mechanism is analyzed by studying the infiltration characteristics for various squeeze conditions.