AlN Matrix Composites Fabricated via an Infiltration and Reaction Approach

Novel AlN‐based ceramic matrix composites were produced using a two‐step infiltration and reaction process. Molten Al alloy was infiltrated without pressure into preforms containing Si3N4 particles (mixed α and β phases). The resultant composites were heat‐treated, causing hard phases (AlN and Si) to form by reaction of the soft Al with Si3N4. The ceramic content of the final composites was higher than that of the original preform due to volume changes that occurred during the reaction heat treatment. Initial characterization of mechanical properties demonstrated that the composites had hardnesses, Young's moduli, and compresive strengths that compared favorably with traditionally processed AlN. Flexural strength measurements above the melting point of Si indicated that the composites possessed an interconnected skeleton of ceramic.