Effects of thermal conditions on microstructure in nanocomposite of Al/Si3N4 produced by friction stir processing

A novel surface modifying technique has been used for fabrication of surface nanocomposite layer of Al5754/Si3N4. The effect of traverse and rotational speed on peak temperature was investigated. With the decrease of traverse speed the peak temperature was increased. Furthermore with increase of rotational speed the peak temperature was increased but in high rotational speed the variation of peak temperature was slight. Also the effect of traverse and rotational speed on stirred zone area was surveyed. The results showed that rotational speed is more effective on stirred zone area than traverse speed. The effect of rotational and traverse speed on grain size was also investigated. It was observed that with increasing the traverse speed to rotational speed ratio the grain size was increased with the exception of some rotational speed such as 1800 rpm. The Si3N4 particles were uniformly distributed in the aluminum matrix. Also the effect of shoulder penetration on fabrication of surface nanocomposite layer was examined. It was observed that under special penetration shoulder, surface nanocomposite layer can be produced. The microhardness of surface nanocomposites produced under different rotational and traverse speed was also evaluated. (C) 2012 Elsevier B.V. All rights reserved.