Abstract
Friction stir processing (FSP) with single and double pin tools was successfully utilized with the aim of fabrication of Al 6061/CeO2 surface composite layer. It was found that pin geometry (pin number) has played a pivotal role in the improvement of mechanical properties and extra grain refinement. Moreover, results indicated that using a double-pin tool during the process impressively enhanced the distribution of CeO2 particles in the matrix and, subsequently, the ultimate tensile strength was increased about 20% compared to the single pin tool.