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 compo sites (MMCs) by the die-casting technique, experimental data are prese nted for the injection of aluminum-alloy-based melts into fiber prefor ms composed of delta-alumina with silica binder. Preforms of volume fr action 15% were prepared from liquid slurry by vacuum-filtration proce sses. 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 pre heated preform and then die pressure was applied until complete solidi fication was achieved. Thus short-fiber reinforced MMCs were fabricate d by the forced infiltration of molten metals into a fiber preform und er an appropriate injection velocity. The microstructure of the fabric ated preforms and the dispersion states of the fibers were observed. T he preform-deformation behavior of the fabricated composites is discus sed. The breakage of the fibers and the tensile fracture surface of th e composites were observed and mechanical properties, such as tensile strength, modulus and hardness of the MMCs, were measured at room temp erature.