Effect of mechanical milling on the morphology and structural evaluation of Al-Al_2O_3 nanocomposite powders

The morphological and microstructural changes during mechanical milling of Al powder mixed with 2.5, 5 and 10 wt.% Al inf 2 /inf O inf 3 /inf particles were studied. The milling was performed in a planetary ball mill for various times up to 20h. The produced composite powders were investigated using X-ray diffraction pattern (XRD) to elucidate the role of particle size, secondary phase content and milling time on grain size and lattice strain of Al matrix. The aluminum crystallite size estimated with broadening of XRD peaks by Williamson-Hall formula. The morphological changes were studied by SEM technique. The results show that the addition of hard Al inf 2 /inf O inf 3 /inf particles accelerates the milling process, leading to faster work hardening rate and fracture of the aluminum matrix. Furthermore, Al becomes smaller crystallite size during ball milling of Al powder in the presence of Al inf 2 /inf O inf 3 /inf particles. The results revealed that the grain size of milled powders was about 45nm with a noticeable presence of agglomerates. Uniform distribution of nano-sized Al inf 2 /inf O inf 3 /inf particles in the Al matrix could be achieved with increasing milling time.