Microstructural Evolution & Mechanical Properties of ZrO2/GNP and B4C/GNP reinforced AA6061 Friction Stir Processed Surface Composites - A Comparative study

Abstract

Friction Stir Processing (FSP) is a surface modification approach by which the surface characteristics of materials can be improved. The materials that are subjected to the FSP can significantly alter the tribological well as the mechanical and metallurgical features by transforming a heterogenous microstructure to a more homogeneous and refined microstructure. In the present work, Zirconia (ZrO2) and Boron Carbide (B4C) nanoparticles along with Graphene Nano platelets (GNP) were reinforced into the surface of the Aluminum AA6061-T6 alloy by FSP. Studies on the effects of the reinforcement on the mechanical and microstructural changes were carried out. As a result of the FSP, the reinforcement particles are uniformly dispersed on the substrate material’s surface. The zirconia/graphene reinforced aluminum composite (Al-ZrO2-GNP) has a significant improvement in hardness about 130% when compared to the as-received AA6061 alloy whereas the hardness of B4C/graphene reinforced composite has shown an increase of 87% when compared with the base metal. X-Ray Diffraction (XRD), Scanning Electron Microscope, and Field Emission Scanning Electron Microscope images reveal the presence of the reinforcement particles and microstructural changes in the friction stir processed aluminum alloys. The Tensile properties of the developed composites have also increased reasonably when compared to the base metal. Wear analysis was carried out and it was found that the B4C/graphene reinforced surface composite has higher wear resistance (40% increase) when compared to the ZrO2/graphene reinforced surface composite (22%increase).