Dispersion of Carbon Nanotubes in AA6061 Aluminium Alloy Powder by the High Energy Ball Milling Process

Abstract

Multi-wall carbon nanotubes (MWCNT), up to 2% in weight, were dispersed into AA6061 aluminium alloy by high-energy ball milling (HEBM) process, for further consolidation into extruded metal-matrix composites (MMC) bars. Three distinct routes were employed: the simple one step loading of materials inside the milling vials, an ultrasonically assisted dispersion of MWCNT and alloy powder into acetone prior to the milling, and the gradual introduction of MWCNT into the vials, during the milling process. Mixed powders obtained were evaluated in terms of the MWCNT integrity after HEBM, and the dispersion level obtained for several milling times. It was found that MWCNT remain relatively undamaged even for milling times up to 10 h, being embedded into the ductile alloy particles through the breaking/welding process during HEBM. However, shorter milling times result in poor dispersion of MWCNT in the milled powders. This tendency can be improved by using pre-milling mixture procedures, as the ultrasonically assisted wet dispersion of nanotubes and alloy powder.