Microstructures and Mechanical properties of Al-Al2O3 Composites Processed by Disk-HPT and Ring-HPT

Al-Al2O3 composites were produced through consolidation of Al micrometer powders and Al2O3 nano-powders using high-pressure torsion (HPT) with disk-type samples (Disk-HPT) and ring-type samples (Ring-HPT). Pure Al powders were mixed with a 30% volume fraction of Al2O3 powders by ball milling (BM). HPT was conducted at room temperature with a rotation speed of 1 rpm under a pressure of 6 GPa for disk samples and 3 GPa for ring samples. The composites were also processed by HPT without BM for comparison. Agglomeration of Al2O3 particles became diminished and the dispersion of nano-sized Al2O3 particles became finer and more uniform by combination of BM and Ring-HPT. This combined use is more effective than Disk-HPT with BM to obtain a uniform Al2O3 dispersion in the Al-Al2O3 nanocomposites and thus to improve mechanical properties.