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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.

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