Fabrication of metal-matrix composites by the die-casting technique and the evaluation of their mechanical properties

To understand the possibility of the fabrication of metal-matrix composites (MMCs) by the die-casting technique, experimental data are presented for the injection of aluminum-alloy-based melts into fiber preforms composed of delta-alumina with silica binder. Preforms of volume fraction 15% were prepared from liquid slurry by vacuum-filtration processes. To find the optimal conditions for preform fabrication a series of experiments was carried out under various conditions. A controlled amount of. molten metal was poured into the preheated die with the preheated preform and then die pressure was applied until complete solidification was achieved. Thus short-fiber reinforced MMCs were fabricated by the forced infiltration of molten metals into a fiber preform under an appropriate injection velocity. The microstructure of the fabricated preforms and the dispersion states of the fibers were observed. The preform-deformation behavior of the fabricated composites is discussed. The breakage of the fibers and the tensile fracture surface of the composites were observed and mechanical properties, such as tensile strength, modulus and hardness of the MMCs, were measured at room temperature.