Analysis of Mechanical Properties and Microstructural Development in Al2O3/rGO and hBN/rGO Reinforced AA6061-T6 Surface Composites via Friction Stir Processing

Abstract

In the current work, the surface of AA6061-T6 alloy has been modified by friction stir processing (FSP) to assess microstructural development and mechanical behaviour. The grooves were made on the surface of the base alloy to deposit the reinforcements (Al2O3 + rGO), and (hBN + rGO) thus one pass was made with the probeless tool to pack the reinforcements into the groove, and 2 more passes in the same direction to compactly fabricate the FSPed composites. The fabricated specimens showed a decreased grain size along with the uniformly dispersed reinforcements in the stir zone (SZ) which can be observed in the microstructural studies. Furthermore, the altered intensity of the significant X-ray Diffraction (XRD) peaks was observed in the FSPed composites which indicates the reinforced elements as evidence of the uniform dispersion. In comparison of the reinforced elements, the Al2O3 + rGO hybrid reinforcement showcased better results of electrical conductivity and thermal conductivity than the hBN + rGO hybrid reinforcement but a slight reduction when compared to the base alloy AA6061-T6. Increased microhardness of 14.86% and tensile strength of 4.39% with an increase of ductility of 8.64% for hBN + rGO hybrid reinforcement was observed when compared to the Al2O3 + rGO hybrid reinforcement. The impact test was conducted for all the surface composites revealed a significant increase of 8.3% in load absorbing capacity with the hybrid reinforcements hBN + rGO compared to the Al2O3 + rGO reinforcement. These results suggest the promising role of modifying base alloy with surface reinforcements via FSP to improve the material performance.