Role of friction stir processing parameters on microstructure and microhardness of boron carbide particulate reinforced copper surface composites

Friction stir processing (FSP) was applied to fabricate boron carbide (B₄C) particulate reinforced copper surface composites. The effect of FSP parameters such as tool rotational speed, processing speed and groove width on microstructure and microhardness was investigated. A groove was contrived on the 6 mm thick copper plates and packed with B₄C particles. FSP was carried out using five various tool rotational speeds, processing speeds and groove widths. Optical and scanning electron microscopies were employed to study the microstructure of the fabricated surface composites. The results indicated that the selected FSP parameters significantly influenced the area of surface composite, distribution of B₄C particles and microhardness of the surface composites. Higher tool rotational speed and lower processing speed produced an excellent distribution of B₄C particles and higher area of surface composite due to higher frictional heat, increased stirring and material tranportation. The B₄C particles were bonded well to the copper matrix and refined the grains of copper due to the pinning effect of B₄C particles. B₄C particles retained the original size and morphology because of its small size and minimum sharp corners in the morphology.