: In this research two aluminum matrix surface nanocomposites were produced on the surface of Al6061-T6 plate via friction stir processing and their characterizations were investigated. One of them included Al 3 Ni intermetallic compound as reinforcement phase and the other included Al 3 Ni and Al 2 O 3 . To produce Al/Al 3 Ni anocomposite two routes were developed. In the first one, a groove with 2 mm depth was filled by Ni powder. In order to prevent the Ni from being displaced out of the groove, surface repair was accomplished with a modified FSP tool that only had a shoulder and no pin. Then FSP carried out on the surface of sample. In the second route Ni powder was flame sprayed on the surface of Al6061 alloy and then friction stir processing carried out on the surface of the sample. X-ray diffraction pattern showed that Ni powder reacted with aluminum substrate and produced Al 3 Ni as reinforcement phase in both samples. Reaction between aluminum and Ni occurred in the first FSP pass, but it was continued up to 5 passes for more reaction and higher hardness. In all experiments, tool rotation rate, traverse speed and tilt of the spindle towards trailing direction were kept constant as 630 rpm, 100 mm/min and 2 0 , respectively. Microhardness measurements showed the same results for both methods. So, to produce Al/Al 3 Ni-Al 2 O 3 , the first technique was employed but NiO powder was used instead of Ni powder. XRD results showed that NiO powder reacted with aluminum substrate and Al 3 Ni and Al 2 O 3 were produced as reinforcements. Microstractural examination was done using both scanning and transmission electron microscopies. Mechanical properties of samples were characterized by microhardness, tension and hot wear tests. Because of T6 condition of Al6061 samples, microhardness and ultimate tension strength of nanocomposite samples decreased, but hot wear test results indicated improvement of wear behavior of both nanocomposites at 400 0 C. Scanning electron microscopy was used for more accurate examination of fracture and wear surfaces. Keywords : Aluminum matrix nanocomposite, Friction stir processing, Al-Ni intermetallic compounds, Hardness, Wear.
