STUDIES ON STRENGTH ENHANCEMENT AND POROSITY REDUCTION IN MMCs BY FRICTION STIR WELDING PROCESS

Abstract

Metal matrix composites are suitable materials for engineering applications encountering surface interactions. Friction stir processing (FSP) is emerging as a promising technique for making surface composites. In this present study by friction stir processing the usage of particulate reinforced metal matrix composite (MMC) is steadily increasing due to its properties such as high specific strength, high specific modulus and good wear resistance. The welding parameters such as welding speed, tool rotational speed and profile of the tool are considered for analysis and the effect of the reinforcement particles on the mechanical properties of the metal matrix composite will be studied. The work piece (AA 7075) of cross-section 120 mm×100 mm and 6.35 mm thickness is prepared and a rectangular groove of depth 2.5mm and width 1.2 mm is prepared on the surface of work piece along the length. The experiment is carried out with and without incorporating SiC particles along the joint line at different FSP process parameters. Cross-sectional microstructures of the joints are characterized employing optical and scanning electron microscopy (SEM). The results show that the Ultimate tensile strength (UTS) of FSPed specimen with SiC reinforcement is higher than the FSPed specimen without SiC reinforcement. Maximum UTS is obtained at FSP process parameters of rotational speed (N=931rpm) and transverse speed (v=34mm/min) including SiC reinforcement due to formation of good bonding at the interface of Al7075 matrix and SiC reinforcement. The presence of SiC particles in AA 7075 matrix are confirmed by EDX and XRD experiments. Porosity contents are reduced due to formation of strong interfacial bonding between SiC particles and AA7075 matrix at FSP parameters of rotational speed (N=931rpm) and transverse speed (v=34mm/min). Optical microscope and SEM image at FSP parameters of rotational speed (N=931rpm) and transverse speed (v=34mm/min) shows the uniformly distribution of SiC particles and excellent interfacial bonding is achieved at the interface of SiC particles and Al matrix.