Ball Milled Al Spheres for the Manufacturing of Casting-Based Al-CNT Composites

Carbon nanotube reinforced aluminum matrix composites are considered a promising solution for applications that require high specific mechanical properties. Even though there are numerous methods for their manufacturing, these are frequently based on powder metallurgy approaches, limiting the fabrication of components with significant volumes and complex shapes. Casting, as a manufacturing technique, is regarded as the most appropriate route to obtain complex-shaped components with a relative high microstructural quality. These techniques to obtain Al-CNT cast components is still challenging due to the agglomeration, lack of dispersion, reduced bonding and density of the CNTs in Al. To address these issues, CNTs are usually pre-processed by ball-milling with Al powder to promote bonding and disperse the reinforcement, however, these techniques are not really beneficial to casting approaches due to the increase of Al2O3 content that do not disperse within the Al alloy melts. This study proposes the use of Al spheres (~1 mm) in these ball milling techniques to prevent significant plastic deformation, the formation of Al flakes and the increase in Al2O3 content. It is shown that CNTs may be dispersed and bonded to the Al sphere surfaces. Results suggest that this is a promising novel technique to allow a successful implementation of casting-based routes to fabricate high-volume and complex-shaped Al-CNT components.