Short alumina fiber-reinforced aluminum alloy composites were fabricated by squeeze casting, and the effects of the fiber reinforcement on the machinability of the alloy under various cutting conditions were investigated. Al-Si-Cu-Ni-Mg alloy (JIS-AC8A alloy) was used as the matrix metal. The mean values of the cutting force of the AC8A alloy were reduced by the fiber reinforcement. The lower the hardness of the fiber in the composite, the lower the cutting force of the composite. The range of the variation in the cutting force during the cutting of the composite reinforced with lower-hardness alumina fibers was almost the same as that of the AC8A alloy. The roughness of the machined surface decreased by the fiber reinforcement under every cutting condition, and the roughness of the composites was almost the same as the theoretical roughness when the cutting speed and feed rate were high. This result indicates that the fibers in the composite suppress the formation of the built-up edge. The machined surfaces and chip forms indicated that the fibers in the composite facilitated the shear deformation of the chips because the fibers were easily sheared by the cutting. These results lead to the conclusion that the machinability of the composites is superior to that of the AC8A alloy.

The possibility of turning fiber-reinforced aluminum alloy composites using a carbide tool was examined. Two types of short alumina fibers, which have the same fiber size, but a different chemical composition and hardness, were used as the reinforcements. The composites were fabricated by squeeze casting. Optical microscopy revealed that the fibers were randomly arranged in the alloy matrix. Fiber reinforcement decreased the cutting force and feed force of the aluminum alloy. The lower the hardness of the fiber in the composite, the lower the cutting force and feed force of the composite. The roughness of the machined surface was significantly decreased by the fiber reinforcement under every cutting condition. Observation of the chip formed on the machined surface indicated that the decrease in the surface roughness by the reinforcement was due to the suppression of the built-up-edge formation. Roughness values of the machined surface of the composite were similar to those when a diamond tool was used. The decrease in the hardness of the fibers in the composite had a significant effect on providing the long tool life.

State of technologies in Japan related to composite casting was reviewed based on the three year survey of Composite Casting Process Sub-Committee in Committee on Foundry Technology (24th) of JSPS. Other than making metal matrix composite, cast-in insertion, bonding and joining of cast materials and other technologies combining different materials by casting process were included. Basic theories and the key technologies are explained, and a number of typical examples of products, on production or on experimental bases, were reported. Overseas literatures were also surveyed.

Aluminum alloy composites reinforced with the short potassium titanate fibers were fabricated to obtain a material having a low thermal expansion rate and good machinability. The composites were fabricated by the squeeze casting. The microstructure, thermal conductivity and thermal expansion behavior of the composites were investigated. Optical microscopy revealed that the fibers were homogeneously distributed in the alloy. However, the fibers were somewhat in a random planar arrangement parallel to the pressed plane when the fiber volume fraction was high. This is due to the forming of the preform by pressing the top and bottom of it. The composites were easily machined using both super alloy and diamond cutting tools. The thermal conductivity of the composite decreased as the fiber volume fraction increased. At the higher volume fraction, the thermal conductivity of the composite in the direction parallel to the pressed plane was higher than that in the transverse direction due to the random planar arrangement of the fibers. The thermal conductivity can be roughly estimated by Landauer's model. The average thermal expansion coefficient of the composite decreased as the fiber volume fraction increased. The difference in the thermal expansion coefficient between the parallel and transverse directions to the pressed plane was slight, and the experimental values were in good agreement with the theoretical values calculated using the rule of mixture.

Alumina short fibre preforms were fabricated using an Al 2 O 3 binder and infiltrated with aluminium piston alloy melt by squeeze casting. Al 2 O 3 binder is thermodynamically more stable than the conventional SiO 2 binder and reduces the fibre/matrix interfacial reaction. The effects of fibre volume fraction, temperature and heat treatment on the yield strength and tensile strength of the composite were investigated. The Al 2 O 3 binder provided a satisfactory interfacial bond between the fibre and the matrix without any interfacial reaction or fibre damage. Aging behaviour was not changed by reinforcement. At every temperature, the composites showed the highest strength with a fibre volume fraction of 18%. The strength of the composite was improved by T6 heat treatment. Examination of the fracture surfaces and calculation of the tensile strength using the rule of mixtures indicated that the 18% fibre reinforced composite had a strong interfacial bond even at high temperatures.IJCMR/458