Huchler, Bernd Arthur (2009)
Ph.D. thesis, University of Birmingham.
In the pressure infiltration processing of Metal Matrix Composites (MMCs), molten metal is injected into a porous preform. This research investigated ways to optimize the processing and properties of MMCs with Al alloy matrices. A ceramic volume fraction of 0.30 to 0.40 was used to keep a preponderant metallic behaviour and the reactivity of MgO, TiO2, Al2O3-SiO2 and Al2O3-TiO2 preforms was compared to pure Al2O3. Two stages were found during infiltration: first, flow initiation characterised by the dynamic wetting angle θdyn and, second, the advancing flow in the preform capillaries. Reactions were detected in the MMC but did not significantly influence the θdyn. Unsaturated fluid flow was evaluated for the subsequent infiltration stage and good agreement was found between a numerical model and experimental data. The MMCs had improved properties compared to the pure alloy. Elastic moduli up to 148 GPa, bending strengths up to 456 MPa as well as reduced wear rate were found. The wear performance of extended ceramic ligaments, found in MMCs with spherical metal ligaments, exceeded all other materials. The improved understanding of the infiltration of preforms and the resulting MMC properties obtained in this research should lead to the development of tailorable composite materials.
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