Microstructural and Mechanical Characterization of CNT- and Al₂O₃-Reinforced Aluminum Matrix Nanocomposites Prepared by Powder Metallurgy Route

In this work, carbon nanotube (CNT) and alumina (Al₂O₃) nanoparticles have been incorporated into the pure aluminum (Al) matrix using ball milling as a part of powder metallurgy route. The benefits and limitations of addition of different amounts of CNT and Al₂O₃ nanoparticles into pure aluminum matrix have been investigated. Different amounts of CNT and Al₂O₃ nanoparticles were dispersed into pure Al matrix using ball milling at different times from 0.5 h up to 12 h. Composite powders were consolidated by uniaxial cold pressing at a pressure of 150 MPa followed by sintering at 530 °C under argon atmosphere. From microstructural point of view, ball milling was found to be an effective method for dispersion of CNT and Al₂O₃ nanoparticles within pure aluminum matrix. It should be noted that there is limitation when a large weigh fraction of CNTs is used. It was found that the threshold of CNTs is 2 wt.%; however, up to 10 wt.% of Al₂O₃ nanoparticles can be used. Most of Al-CNT and Al-Al₂O₃ nanocomposites were found to reach steady state after 8 of milling except Al-5CNT and Al-10CNTs which never reached steady state due to the formation of big agglomerates resulting in non-homogenous nanocomposite powders. Young’s modulus and hardness of Al-CNT nanocomposites were found to be higher than Al-Al₂O₃ nanocomposites, while a homogenous dispersion of reinforcements within matrix was observed.