Influence of carbonaceous agrowastes nanoparticles on physical and Mechanical properties of friction stir processed AA7075-T651 metal matrix composites

Abstract

Friction Stir Processing (FSP) is a mode of surface enhancement used to improve the properties and the surface quality of the fabricated samples. The main focus of this research was to make a comparative performance assessment using economical and eco-friendly carbonaceous agro-wastes nanoparticle as reinforcement in AA7075-T651 during FSP and to determine the surface roughness and the tensile strength of the produced samples. Nanoparticles of Wood fly ash (WFA), coconut shell ash (CSA), coal fly ash (CFA), palm kernel shell ash (PKSA) and cow bone ash (CBA) were developed. The processing parameters used on the FSP machine were rotational speed of 1500 rpm, 20 mm min−1 processing speed, 3° tilt angle, and 0.3 mm plunge depth. The physical and the mechanical properties of the fabricated samples were studied. Results revealed that metal matrix composites (MMC) reinforced with WFA-NPs has the best surface integrity with the least Ra of 1.60 μm, followed by AA7075-T651/CBA-NPs with Ra value of 2.81 μm while unreinforced but processed base metal (UBM)- AA7075-T651 was the roughest with Ra value of 11.61 μm. It was further observed that UBM produced the highest ultimate tensile strength (UTS), Rm with a value of 620.9 MPa, and this also produced the highest yield strength at 0.1%, 0.2% and 0.5% off strain given the following values 599.1, 572.9 and 588.5 MPa respectively. Amongst the fabricated MMC, the one reinforced with carbonaceous CSA-NPs produced the highest UTS, Rm with 379.9 MPa while there was tie values in UTS, Rm for WFA-NPs and CFA-NPs which was 367.8 MPa and AA7075-T61/CBA-NPs gave the least value of UTS, Rm with a value 298.1 MPa. Most of the fractured surface areas of the nanocomposites are dominated by the dimples-induced transgranular agreeing with the remarkable interfacial bonding with the aluminium matrix composites.