Book excerpt: The feasibility of fabricating fiber-reinforced aluminum alloys by addition of discontinuous fibers to partially solid slurries and completely liquid matrices was investigated. In the first phase of the program, emphasis was placed on the study of interface interactions between polycrystalling Al2O3 fibers and Al-2 to 8%Mg, Al-4.5%Cu and Al-4.5%Cu-1 to 2%Mg alloys produced by the slurry process. In general, it was observed that the incorporation of fibers could be readily achieved by this technique, and that fibers appeared wetted after a few minutes of contact with the melt. The composites produced exhibited an intimate, void free bond between the constituents. In addition, a region of significantly altered microstructure resulted from accumulation of oxide and/or aluminate particles which either formed within the melt and were attached to the moving fibers, or used the fiber surface as a substrate to grow on. Microscopic examination of this interaction zone and thermodynamic considerations indicated that it consisted of fine alpha-Al2O3, aluminates, oxides of the alloying elements, and probably some intermetallic compounds.