Mechanochemical synthesis of Cu-Al2O3 nanocomposites

Nanocomposite powders of Cu-Al2O3 were produced by simple milling at room temperature in high-energy attritor mill using mixtures of Cu, Cu2O and Al powder ingredients. The milled powders were then consolidated by hot pressing (HP) in high-density graphite die at 800, 850 and 900 °C under 50 MPa. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations showed that the consolidated materials were comprised of a mixture of nanocrystalline fcc-Cu and α-Al2O3 phase. The results of microstructural analysis also showed that Cu grains were of order of 20-30 nm with a bimodal size distribution of Al2O3 dispersoids: the coarse dispersoids are about 50-100 nm and fine ones about 10-20 nm. Average hardness number of the hot pressed materials consolidated at 850 °C increases from 70 to 103 HRB (Rockwell hardness number) with increasing vol.% of Al2O3.