Co-continuous Al/Al2O3 composite produced by liquid displacement reaction: Relationship between microstructure and mechanical behavior

Co-continuous 63%Al2O3/37%Al(Si) composite, known as C4 composite, was produced by submersion of silica glass specimens in a molten metal bath. The effect of temperature and composition of the metal bath on the reactive penetration rate was investigated. An infiltration speed exceeding 2 mm/h, increasing with temperature, and suitable for practical applications, was observed above 1100°C. Mechanical properties of C4 specimens were measured, at room temperature, and related to composite microstructure. This latter was investigated by optical and scanning electron microscopy, electron probe microanalysis, X-ray diffraction and porosimetry. The strong interfacial bonds between metal and ceramic resulted in low thermal expansion, high stiffness, and good compression and bending strength. On the contrary, the composite showed a rather poor tensile strength, due to a high ceramic percentage and, partially, to porosity. In spite of the low ductility shown by the investigated composite, the metal network provides a toughening effect, which resulted in a ductile micro-mechanism of fracture, localized in the zones characterized by the presence of the metal matrix.