Processing of Mullite–Aluminum Composites

Abstract

Interconnected‐phase mullite–aluminum metal–ceramic composites were processed using the indirect fused‐deposition process. In this process, controlled‐porosity ceramic preforms were fabricated via the lost‐mold process. The molds were designed with computer aided design (CAD) software and fabricated using a fused‐deposition modeling (FDM) technique. Porous ceramic preforms were infiltrated with aluminum metal, via pressureless reactive metal infiltration, to form the mullite–aluminum composites. Both the macrostructures and the microstructures of the composites were controlled via CAD and FDM. During metal infiltration, the mullite phase transformed to α‐alumina, and an alumina–aluminum composite formed. This paper describes the mullite‐to‐alumina phase transformation during reactive metal infiltration of the porous preforms, as a function of processing variables.