Liquid metal infiltration has become the most convenient and productive method to fabricate a wide variety of metal matrix composites. Far to be simple, it displays a very rich phenomenology encompassing, among other interesting variables, chemical interactions between liquid metal and reinforcement.
Reactivity can improve or hinder infiltration, depending on several factors. Given that many metal/ceramic couples are defined as non-wetting systems, infiltration needs to be pressure-assisted. If metal entrance pace into the porous preform is high, reactivity and infiltration are decoupled in time and an a priori reactive system can be treated as non-reactive. If metal entrance pace is low, infiltration and chemical interactions between liquid metal and preform take place simultaneously and permeability of the porous body can be greatly altered due to the growing of new crystalline phases formed as a consequence of reaction. In these cases, obstruction of open pores in the preform can seriously hinder infiltration.
Some of the high-end applications in the actual market for which composite materials are designed require a unique combination of properties which can only be achieved if the chemical nature of the interface between phases is perfectly controlled at the level of micro- or nano-scale. In other words, conclusive experimental results have demonstrated that a certain degree of interface chemical evolution turns out to be essential to achieve the right properties for technologically interesting materials. For this to be reached, and at the same time ensure that the level of penetration of the metal will not diminish due to reaction-caused hindering, both infiltration and reactivity kinetics have to be known and controlled during the processing of the composite materials.
In this contribution we comment on different considerations which are essential in the processing of composite materials with technological interest.