Effect of process modification on the microstructure and properties of fiber reinforced metal matrix composites

A modified pressure infiltration process was recently demonstrated to synthesize carbon fiber reinforced aluminum matrix composites. In this process the pressure infiltration set up is modified to extend the ends of carbon fibers out of the crucible to act as a conduit to remove heat from the system. The carbon fibers are coated with nickel to avoid direct contact between aluminum and carbon. Contact between fibers and aluminum melt results in the formation of brittle Al ₄C ₃ and is detrimental for the properties of the composite. The process modification is found to be effective in experimental studies in minimizing the damage to the nickel coating during the infiltration process. The present work is focused on modeling the modified process using finite element analysis (FEA) and quantifying the effect of conductive heat transfer from the system on the microstructure of the material. Due to axisymmetry of the system, a two-dimensional model is developed. The solutions can easily be extended to three-dimensions. The transient behavior of the system is analyzed in the study. The results show that a change in the fiber radius is more effective than a change in the fiber length in controlling the heat transfer from the system. This result can be used in determining the optimum fiber volume fraction in the composite materials for obtaining the desired microstructure.