Chip Formation in Machining Particle-Reinforced Metal Matrix Composites

This paper compares the chip forming mechanism in monolithic metals and in particle-reinforced metal matrix composites. A quick stop device was designed to collect the chip-root for microscopic examination. The eutectic silicon and reinforcing particles formed flow lines due to different velocity zones across a chip. The reinforcing particles interfered with plastic deformation of the matrix, retarded crack growth, and were not delaminated from the matrix. High local temperature, induced by high strain rate in machining, improved the material ductility and healed microcracking in a chip. Heat treating a composite to a T6-temper affects the shear deformation at the tool-chip interface, and shortens the tool life.