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

Abstract

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.