Hot deformation and activation energy of a CNT-reinforced aluminum matrix nanocomposite

Hot deformation behavior of a 2.0 wt% CNT/2024Al nanocomposite was studied via high-temperature compression over a temperature and strain rate range of 200-400 °C and 0.001-0.1 s−1, respectively. Both flow stress and Zener-Hollomon parameter increased with decreasing deformation temperature and increasing strain rate. The addition of CNTs led to a significant increase of activation energy of plastic deformation, corroborating the enhanced resistance of the nanocomposite to hot deformation. This was also reflected by the increased compressive yield strength in the nanocomposite due to both Hall-Petch strengthening and effective load transfer of CNTs dispersed in the matrix with well-bonded interfaces. Detailed microstructural examinations at a high strain rate, within the upper and lower temperature limits, revealed the occurrence of second-phase particle shearing, refinement, re-precipitation, and re-orientation. The highly beneficial role of the CNT reinforcement in improving the high-temperature performance of Al alloys was discussed.