Mechanical Properties of AA2024 Aluminum/MWCNTs Nanocomposites Produced Using Different Powder Metallurgy Methods

Metal matrix composites are a class of materials with high potential for industrial application due to the multifaceted properties that they possess. In the present research, mechanical alloying via ball milling was used to produce AA2024 powder that was subsequently reinforced with multiwalled carbon nanotubes (MWCNTs). Dispersion of the MWCNTs in the AA2024 matrix was achieved also by ball milling. Two different powder metallurgy sequencies, (i) double pressing double sintering and (ii) hot pressing were used for compaction and consolidation of the AA2024 reinforced by MWCNTs. The produced nanocomposites outperform the pristine AA2024 in terms of compressive strength, elongation to failure, and microhardness. The strengthening mechanism was associated with the homogeneous distribution of MWCNTs in the AA2024 matrix and their efficient interfacial bonding, which was attested also by microstructural characterization. Hot pressing resulted in higher mechanical properties of the nanocomposite material. However, when reinforcement content was above 2 wt.% a dramatic decrease of mechanical properties was observed, attributed to clustering and inhomogeneous dispersion of the MWCNTs. The homogeneous dispersion of MWCNTs in the AA2024 matrix and the retaining of their structural integrity are pivotal in increasing the mechanical properties, which can be directly associated with the efficient interfacial load transfer between MWCNTs and AA2024 matrix.