ALN MATRIX COMPOSITES FABRICATED VIA AN INFILTRATION AND REACTION APPROACH

Novel AlN-based ceramic matrix composites were produced using a two-st ep infiltration and reaction process. Molten Al alloy was infiltrated without pressure into preforms containing Si3N4 particles (mixed alpha and beta phases). The resultant composites were heat-treated, causing hard phases (AlN and Si) to form by reaction of the soft Al with Si3N 4. The ceramic content of the final composites was higher than that of the original preform due to volume changes that occurred during the r eaction heat treatment. Initial characterization of mechanical propert ies demonstrated that the composites had hardnesses, Young's moduli, a nd compressive strengths that compared favorably with traditionally pr ocessed AlN. Flexural strength measurements above the melting point of Si indicated that the composites possessed an interconnected skeleton of ceramic.