Discontinuously Reinforced Aluminum (DRA) Composites form unique case from the research in metal cutting point of view. Reinforcement in these materials acts as “macroscopic” and “isolated” discontinuities in the path of the tool. The mechanism of chip formation for such materials is yet to be evolved completely. In this paper, the mechanism of chip formation during machining of Al/SiCp composites based on the micro-structural analysis of chips and chip roots is presented. It was evident that the mechanism involves initiation of a gross fracture on the chip free surface and its propagation toward the tool nose. The extent of propagation of gross fracture depends upon the cutting speed and volume of reinforcement in composites. A model of deformation of the material along the shear plane is presented in terms of a ratio of length of flow-type deformation on the shear plane to the total length of shear plane. Influence of volume of reinforcement in composites and cutting speed on the ratio was verified experimentally.
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