Correlation of thermal models with microstructural effects in continuous MMC wire production

A recently developed continuous pressure infiltration process at Northeastern University has successfully produced completely infiltrated metal matrix composite (MMC) wires showing high mechanical strength. Thermal models are developed for two key regions (the entrance and middle orifices) of the high-pressure infiltration apparatus to identify heat transfer conditions that relate to process limitations and resulting MMC microstructure. For composites composed of 2024-aluminum alloy with alumina fiber reinforcement, experimental measurement of resulting grain size and solute segregation are compared for two processing velocities. At lower pulling velocity, the overall average matrix grain diameter (3.92 μm) is larger than that measured at higher pulling velocity (1.84 μm). Segregation is notably higher at lower pulling velocities. Predictions from thermal models correlate with microstructural observations, and are utilized to determine a maximum processing velocity for improved process control.