Reactive milling synthesis of nanocrystalline Al-Cu/Al₂O₃ nanocomposite

Nanocrystalline Al-4 wt% Cu alloy reinforced with nanometric Al₂O₃ particles was synthesized by in situ reactive milling of Al and CuO powder mixture. X-ray diffraction (XRD), differential thermal analysis (DTA) and transmission electron microscopy (TEM) techniques were employed to study the mechanically induced solid state reaction between the blended powders. The mechanical milling stages were studied by scanning electron microscopy (SEM), bulk density measurement and laser particle size analyzer. It was shown that the reaction between Al and CuO occurs progressively as the mechanical milling continues, leading to formation of nanoscaled alumina particles. The grain refinement of the matrix by severe plastic deformation also resulted in the formation of nanocrystalline Al-Cu alloy. It was determined that the FCC Al (Cu) solid solution has a lattice parameter of 4.04 Å, average crystallite size of about 50 nm and lattice strain of 0.35%. The size of alumina particles was in the range of 10-50 nm and they were mostly distributed at the grain boundaries. The processed nanocomposite powder has fine and equiaxed particles with relatively high bulk density. This paper presents structural evolution and morphological changes occurring during attrition milling of Al-CuO powder mixture.