The aim of the present investigation was to develop Al6061/TiB 2 nanocomposites via mechanical route in order to improve the mechanical properties in particular wear behavior of Al6061 alloy. For this purpose, the mechanical and tribological properties of bulk Al6061/TiB 2 nanocomposites, produced by mechanical alloying and hot pressing, were investigated. The TiB 2 nanoparticles, synthesized by 20 hr milling of Ti-B powders were added to the elemental powder mixture of the Al6061 matrix to produce Al6061-20 wt.% TiB 2 nanocomposite. also a double step milling process was used in order to synthesize the Al6061-20wt.% TiB 2 nanocomposite via in-situ route. At the first step, Al-90wt.%(Ti, B) was milled for 20 hr to form TiB 2 reinforcements in the aluminum matrix. A stoichiometric mixture of Al, Mg and Si powder was then added to this powder and the A6061-20 wt.% TiB2 nanocomposite was synthesized by further mechanical alloying for a 10 hr. In order to study the structural and morphological as well as hardness changes of the powder products, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Vickers microhardness test were used. Bulk nanostructured samples were then synthesized through hot pressing of the milled powders and the mechanical and tribological properties of consolidated samples were investigated. Hardness of the bulk nanostructured Al6061 alloy was about 125(HV.), which is much higher than that of commercial Al6061 alloy (65 HV.). Hardness of the ex-situ and in-situ nanocomposites was measured to be about 160 and 200 (HV.) respectively. Improvement of the tribological properties of Al6061 matrix (decrease in wear rate and friction coefficient) was attributed to the nanosize structured along with the presence of nanosized reinforcements. Reinforcements introduced via in situ route had more effect on the reduction of wear rate in comparison with that produced via ex-situ routes. Wear mechanisms of the samples were investigated by SEM and EDS analysis of the wear products and surfaces. In general bulk nanocrystalline and nanocomposite Al6061 samples exhibited improved wear resistance and lower adhesive wear rate. Keywords: Al6061 alloy, TiB 2 reinforcement, nanocomposite, mechanochemical, in-situ reaction, tribology
