Mechanical milling of Al and synthesis of in-situ Al2O3 particles by mechanical alloying of Al-CuO system

Abstract

Initially, pure Al was milled for upto 20 h in order to find out the milling characteristics of Al. The effect of milling on the crystallite size, lattice strain, lattice parameter and the melting characteristics of Al was determined. Later Al-5 vol. % CuO was milled to investigate the possibility of synthesis of in-situ Al2O3 by mechanical alloying (MA) and subsequent annealing of the milled powder. The DSC plot of the 25 h milled Al ponder shows an exothermic peak of crystallization instead of an endothermic peak due to melting. In-situ α-Al2O3 reinforcing particles have been successfully synthesized by annealing of the 25 h milled Al-5 vol. % CuO powder mixture. Al-5 vol. % CuO powder mixture was initially milled for 25 h and later annealed at 650 °C and 1100 °C for a period of 2 h. Various techniques like differential scanning calorimetry (DSC), differential thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) have been used to investigate the formation of phases during MA and subsequent annealing of the milled product. The formation of in-situ nanostructured α-Al2O3 particles was confirmed by annealing of the 25 h milled Al-5 vol. % CuO powder mixture at 650 °C and 1100 °C for 2 h. The exothermic reaction between Al and CuO represented as 2Al + 3CuO→ Al2O3 + 3Cu was induced by MA and was later completed during annealing.