The production and evaluation of metal-matrix composite castings produced by a pressure-assisted investment casting process

Abstract

A process for the production of aluminium alloy metal-matrix composites (MMCs) by the liquid metal infiltration route is presented. This process was based on investment casting to enhance its ability to cast complex 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, squeeze casting has limitations in respect of die design and complexity. This new process, referred to as the ‘hybrid process’ in this paper, combines the advantages of the squeeze casting and investment casting processes. Tensile test results of as-cast specimens at room temperature are reported for the investment casting, squeeze casting, and hybrid casting processes. The hybrid casting process produced MMCs with tensile strengths equal to 80% of those obtained in squeeze infiltrated composites produced at the optimum processing conditions. The Al-7%Si alloy and δ-Al 2O 3 short fibre composite system was used for this work.