In the present study mechanical milling used to form nanocrystalline structure in Al-Al2O3 powders. The microstructure of the milled powders was investigated by X-r ay diffraction (XRD) analysis. It was found that the XRD peaks showed a significant broadening, which was related to grain refinement and lattice distortions. X-ray patterns were analyzed using Williamson–Hall treatment to determine the crystallite size and the lattice strain. nanocrystalline powders have been synthesized with microstructure showing a higher lattice strain and an evolution of the finest particles. Microhardness measurements and compression tests were performed to characterize the composite materials.