Mechanical properties of nanostructured Al2024–MWCNT composite prepared by optimized mechanical milling and hot pressing methods

Nanostructured Al2024–multiwall carbon nanotubes (MWCNTs) composites were produced using optimized mechanical milling and hot pressing methods. Nanostructured Al2024 powder was first prepared through 30 h mechanical milling of the alloy powder. MWCNTs up to 3 vol.% were added to the milled Al2024 powder and milled for different times. Differential thermal analysis (DTA) and X-ray diffraction (XRD) were used to assess the structural changes and thermal behavior during mechanical milling and hot pressing. Hardness and compression tests were applied on bulk samples to evaluate their mechanical properties. Mechanical milling applied on Al2024 powders for 30 h resulted in the grain refinement to ∼30 nm. DTA analysis showed an endothermic peak at ∼632 °C due to Al2024 melting and an exothermic peak between 645 and 658 °C related to Al and MWCNTs reaction. Mechanical milling of nanocomposite powder for 4 h and following hot pressing at 500 °C under a pressure of 250 MPa for 0.5 h were selected as optimized conditions for bulk nanocomposite preparation. With MWCNTs addition up to 2 vol.%, relative density remained at 98%, and hardness increased to 245 HV. Compressive strength of nanocomposites found a maximum value of 810 MPa at 2 vol.% MWCNTs addition which is 78%, 34% and 12% greater than that for Al2024–O, Al2024–T6 and nanostructured Al2024, respectively.