Elucidation of the role of rotation speed and stirring direction on AA 7075-B4C surface composites formulated by friction stir processing

In the present research investigation, aluminum–boron carbide surface composites were fabricated using friction stir processing technique. Boron carbide powder particles were incorporated into AA 7075 substrate by the thermomechanical mixing generated through multiple passes of friction stir processing. A parametric investigation was conducted to encounter homogeneous boron carbide powder particles distribution in the substrate matrix by employing various parameter combination sets like tool rotational speed and alteration in tool travel direction. Microstructural characterizations were performed by means of optical microscopy, scanning electron microscopy and X-ray diffraction analysis to investigate on boron carbide powder particles distribution, phases present, and grain morphologies in the substrate matrix. Homogeneous distribution of boron carbide powder particles was observed for surface composites processed at lowest tool rotational speed. Uniform boron carbide powder particles distribution in the processed zone along with various strengthening mechanisms brought about two-fold increase in microhardness and wear resistance of the prepared composites.