Characterization of Hot Deformation Behavior of Nanosized Al₂O₃ Reinforced Al6061 Composites.

The hot deformation behavior of Al6061/Nano-Al₂O₃ composites were investigated at temperatures of 300 to 500 °C and strain rates of 0.001∼1/s using compression tests. The composite fabricated by the infiltration method consisted of an Al matrix and Al₂O₃ particles with a mean size of 200 nm. Interestingly, the true stress-true strain curves under all compressive conditions showed a peak stress at the initial stages of deformation, in which the peak stress increased with decreasing temperature and faster strain rate. The parameter, which is known as the temperature-compensated strain rate showed a linear relationship with the flow stress. The hot deformation mechanism is believed to occur through dynamic recrystallization, where fine equiaxed grains and dislocations were observed at the deformed specimens. A processing map was applied to evaluate the hot workability and flow instability region to determine the optimal deformation conditions of the composite.