Development of the technique of extrusion directly following infiltration for the manufacturing of metal-matrix composites

Metal-matrix composites (MMCs) are now attracting increasing interest because they exhibit improved physical and mechanical properties as compared with the matrix alloys. Although the properties of MMCs are determined primarily by the individual properties of the matrix alloy and the reinforcing material, yet the former are also influenced largely by the manufacturing technique. To obtain MMCs with optimum properties, the manufacturing technique has to assure uniform distribution of the reinforcing material in the matrix and the formation of a good bond between the matrix and the reinforcing phase. Voids must be eliminated also, as well as direct contact bridging or bunching of the reinforcing phases. For this reason, a new technique, extrusion directly following infiltration (EDFI), is proposed. The new technique is developed on the basis of melt infiltration, squeeze casting, and semi-solid extrusion techniques and is particularly suitable for the manufacturing of bars, pipes, plates, and other long shapes of discontinuous fiber, whisker, or particulate reinforced MMCs. This paper presents a detailed description of the technique in principle and a discussion of the experimental results obtained from technical experiment with short alumina fiber and Al-1.5%Mg aluminum alloy.