Impact of alumina content and morphology on the mechanical properties of bulk nanolaminated Al2O3-Al composites

YYY Aluminum-based composites made by powder metallurgy often include a nontrivial amount of alumina whose effect is mostly neglected or insufficiently discussed as compared to the primary reinforcing agent. In this study, by controlling the composite processing atmosphere, we systematically studied the impact of alumina content and morphology (particularly the aspect ratio) on the microstructure and mechanical properties of bulk nano laminated Al2O3-Al composites. It was found that, even with full-glovebox control over the entire powder metallurgy-based fabrication process, there was still approximately 1 wt% oxygen in the as-fabricated composite. However, the processing atmosphere profoundly affected the microstructure and the size and morphology of the alumina reinforcement in the aluminum matrix, and subsequently the mechanical behavior of the composites. These observations were interpreted by the alumina load-sharing through the shear-lag mechanism in samples with large alumina aspect ratios and the combined effect of the Orowan-typed mechanism in samples with small aspect ratios.