Fabrication of Al 2024-boron carbide surface nano composite by friction stir processing

The purpose of this investigation was the fabrication of surface nano composite composed of aluminum 2024 and boron carbide particles with the average size of 60 nm by the friction stir processing (FSP) method. The primary FSP tests showed that the rotating speed of 850 rpm and traverse speed of 25 mm/min are the optimum conditions which results in sound defect free samples. Then, the effect of nano particles addition and number of passes were analyzed in the fabricated samples. Optical and field emission scanning electron microscopy techniques showed that the average grain size in the stirring zone decreases by adding nanoparticles to the matrix and increasing the number of FSP passes. The hardness and the abrasion tests showed that strength and wear resistance of the fabricated samples increases with increase in number of passes. The improvement in the mechanical properties was attributed to the uniform distribution of the reinforcing particle and grain refinement. However, in the FSPed base metal the hardness was decreased due to the dissolution of primary strengthening particles during the FSP process. The result of electrochemical tests indicated that corrosion behavior of the FSPed samples improves by adding the reinforcing particles and increasing the pass number.