Reinforcing aluminum matrix with much smaller particles, submicron or nano-sized range, is one of the key factor in producing high-performance composites, which yields improved mechanical properties. High-energy ball milling was successfully employed to synthesize nano-crystalline Al7075 alloy powders reinforced with 1, 3 and 5 vol.% Al2O3 at nano-size level. Hot pressing was employed to consolidate the green powder metallurgy products. The nano-composite powders were characterized by SEM, TEM, and XRD. Using Williamson-Hall equation, crystallite size and lattice strain of various Al7075 composite powders were estimated with broadening of XRD peaks. XRD results showed that the crystallite size of aluminum reached 42.30, 36.25 and 32.22 nm, respectively, after 20 h milling in case of Al7075/1, 3, and 5 vol.% Al2O3 nano-composite powder with uniform particle size distribution. TEM observation confirmed the nano-crystalline nature of Al7075/5 vol.% Al2O3 milled powder. Mechanical measurements showed that the hardness and ultimate tensile strength of the Al7075-nano Al2O3 tend to increase with increasing nano Al2O3 volume content at the expense of tensile ductility. (C) 2012 Elsevier B.V. All rights reserved.