In our previous study, a bulk carbon nanotube (CNT)-reinforced aluminum alloy matrix composite with enhanced comprehensive mechanical properties was fabricated via an advanced powder processing, denoted as Mixed Ball-Milling (MBM) technique. Here, we attempted to explore the relationship between the composite microstructure and the elevated mechanical behavior with a special focus on CNT/Al interfacial features. To this end, high-resolution scanning transmission electron microscopy (HRSTEM) imaging combined with Raman spectroscopy were conducted to take a panoramic view of the subject. It was shown that in addition to the matrix heterogeneous grain structure and maintaining the structural integrity of CNTs, the interfacial bonding structure can be tailored using MBM methodology. Indeed, the formation of aluminum oxide nanophases in and around acid treatment-induced oxygen defects not only contributed to CNT structural conservation but also facilitated the load-transfer capability of the composite. A semi-quantitative analysis, performed on Raman spectroscopy data, authenticated that the aluminum carbide (Al4C3) formation was significantly restricted in the MBM pro-cessing, probably due to the presence of oxide species. The findings may also grant insight into the seldom-studied role of surficial oxygen defects in carbon-containing metal matrix composites.

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