Preparation of AlN matrix composites using an infiltration and reaction approach

Aluminum nitride (AlN) matrix composites were prepared by a novel approach. Porous preforms containing Si3N4 and Al2O3 were fabricated after sintered at 1450 °C in N2. Then, molten Al–10Si–5Mg alloy was infiltrated into preforms in air at temperature of 850 and 950 °C to form ceramic/metal composites using the pressure less metal infiltration process. Finally, the as-infiltrated composites were heat-treated to over 1200 °C in air in order to form AlN matrix composites. The test results shown that Si3N4 had reacted with Al to form AlN when molten Al alloy was infiltrated into the porous preforms at 850 and 950 °C, a large amount of AlN phase in the composite was detected after heat-treated at 1200 and 1300 °C. The composites had higher hardness than that of AlN made by traditional processing. The composite microstructures and its phase makeup were observed and analyzed by SEM, EDS and XRD.