THE PRODUCTION AND EVALUATION OF METAL-MATRIX COMPOSITE CASTINGS PRODUCED BY A PRESSURE-ASSISTED INVESTMENT-CASTING PROCESS

A process for the production of aluminium alloy metal-matrix composite s (MMCs) by the liquid metal infiltration route is presented. This pro cess was based on investment casting to enhance its ability to cast co mplex shapes by the fibre preform infiltration method. Squeeze casting has been the most popular route for producing such composites due to its ability to provide high positive pressures to promote infiltration and good bonding characteristics of the fibre preform. However, squee ze casting has limitations in respect of die design and complexity. Th is new process, referred to as the 'hybrid process' in this paper, com bines the advantages of the squeeze casting and investment casting pro cesses. Tensile lest results of as-cast specimens at room temperature are reported for the investment casting, squeeze casting, and hybrid c asting processes. The hybrid casting process produced MMCs with tensil e strengths equal to 80% of those obtained in squeeze infiltrated comp osites produced at the optimum processing conditions. The Al-7%Si allo y and delta-Al2O3 short fibre composite system was used for this work. (C) 1997 Elsevier Science S.A.