ABSTRACT
Friction stir processing (FSP) is a novel technique used for the production of surface composites, refinement of microstructure, and enhancing the mechanical properties. In this work, surface matrix composite was fabricated on the surface of copper with ceramic reinforcement using FSP technique. SiC and B4C were used as reinforcement. The chosen FSP parameters were traverse speed of 40 mm/min, tool rotational speed of 1120 rpm, and 10 kN 164of axial load. The FSP tool made of high carbon high chromium (HcHCr) with cylindrical tapper threaded profile pin having shoulder diameter of 24 mm, pin length of 3.8 mm, and pin diameter of 8 mm was used. The FSP was carried out using friction stir welding machine. Six combinations of surface composites (Cu/2Vol.%SiC, Cu/4Vol.%SiC, Cu/6Vol.%SiC, Cu/2Vol.%B4C, Cu/4Vol.%B4C, and Cu/6Vol.%B4C) were fabricated. The fabricated surface composites were examined by optical microscope for dispersion of reinforcement particles. The tensile properties of the surface composites are better at 4 vol.% of SiC and B4C compared to other vol.% of reinforcements. This is due to the grain refinement of copper in the surface composite which can be related to the interaction between powder particles and dislocations within the matrix. It is also observed that with an increase in the addition of B4C reinforcement particles recrystallization temperature increases by pinning grain boundaries of the copper matrix and blocking the movement of dislocations and; thus, improving the strength. The observed mechanical properties are correlated with microstructure. The microhardness of friction stir processed plates was analyzed using a Vickers hardness tester. B4C reinforced Cu surface composite resulted in higher microhardness.
