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Plate impact experiments were carried out to examine the high strain‐rate tensile response of alumina‐aluminum (Al) composites with tailored microstructures. A novel processing technique was used to fabricate interpenetrating phase alumina‐aluminum composites with controlled microstructures. Fused deposition modeling (FDM), a commercially available rapid prototyping technique, was used to produce the controlled porosity mullite ceramic preforms. Alumina‐Al composites were then processed via reactive metal infiltration of porous mullite ceramics. With this approach, both the micro as well as the macro structures can be designed via computer aided design (CAD) to tailor the properties of the composites. Two sets of dynamic tensile experiments were performed. In the first, the metal content was varied between 23 and 39 wt. percent. In the second, the microstructure was varied while holding the metal content nearly constant. Samples with higher metal content, as expected, displayed better spall resistance. Fo...

Nonrandom porous mullite ceramic preforms were fabricated by the indirect fused deposition process. MgO was added to commercial mullite powders as a sintering aid. The influence of porosity and the amount of MgO on the densification and mechanical properties was studied. The shrinkage and compressive strength of the porous samples were found to increase with increasing MgO content. At constant MgO concentration, shrinkage was found to decrease linearly as the volume fraction of porosity increased. The compressive strength of porous samples decreased with an increase in the volume fraction of porosity at constant MgO content.

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.