Porosity nucleation in metal-matrix composites

The mechanism of porosity nucleation in pressure infiltration casting of me tal-matrix composites (MMCs) is investigated. Five interfacial configuratio ns are investigated for a variety of matrix/reinforcement systems. Interfac es with negative curvature such as cavity are found to be potential sites f or porosity formation. The Al/Al2O3 system is most susceptible to porosity nucleation for the systems considered, Appropriate matrix alloying such as Mg in the Al/Al2O3 system and Mg and Cu in the Al/SiC system and reinforcem ent coatings such as Cu coating on SiC significantly reduce the contact ang le, enhance wettability at the interface, and could be effective for suppre ssing porosity formation. Other effective methods include careful control o f the cooling condition as well as the applied pressure.