Effect of Nanoparticles Addition on Microstructural and Mechanical Properties of Friction Stir Welded 2014 Aluminium Alloy

Abstract

Effect of aluminium oxide nanoparticles (Al2O3 NPs) was studied on the microstructural and mechanical properties of friction stir welded 2014 aluminium alloy to overcome softening in nugget zone. A joint with and without Al2O3 NPs was welded to compare the microstructure, tensile and hardness results. Optical and scanning electron microscope (SEM) was used for investigation of distribution, grain size and grain structure in the stir zone. Transverse tensile test and hardness across the weld surface were carried out to compare the mechanical properties of the joints. The FSW parameters fixed throughout the experiments were 1100 rpm, 30 mm/min of rotation speed and traverse speed, respectively. Microstructure observation indicated that the Al2O3 NPs were distributed uniformly after the third pass and the Al2O3 NPs settled at the grain boundaries in the stir zone which leads to an increase in the weld strength. The grain refinement was successfully achieved after reinforcing nanoparticles in the stir zone of FSW joint. The tensile strength of reinforced FSW joint got enhanced about 22% to that of normal FSW joint. Due to a decrease in grain size and the presence of nanoparticles in the stir zone, the average hardness across the stir zone of the reinforced joint was improved.