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In this article, the effect of vibration and cooling media on the friction stir welding of 5083Al alloy is investigated. The vibration was introduced by the motor into the fixture inserted under the workpiece while a cooling media (water and lubrication oil) flowed into a canal in the fixture beneath the weld path. A constant rotation speed of 1250 r/min and a traveling speed of 90 mm/min were used for all the welding conditions. The thermal analysis measured by several thermocouples indicated that friction stir vibration welding (FSVW) provided maximum temperature distribution in the workpiece, while friction stir welding with the water cooling exhibited the lowest temperature value. The microstructure observations were conducted by optical microscope, scanning electron microscopy, and transmission electron microscopy. The results indicated substantial grain refinement when vibration and water cooling were simultaneously applied during the friction stir welding process. The hardness values increased from 50 to around 78 (Hv) for friction stir welding and FSVW with water systems, respectively. The joint efficiency (the ratio of the joint strength to the base metal strength) of the joint fabricated by FSVW with water cooling was around 87%, while this quantity was about 66% for the friction stir welding joint. Fracture analysis indicated more ductile behaviors for the samples fabricated by FSVW with the coolant systems. Furthermore, the joint fabricated by FSVW with water cooling exhibited the best wear resistance among all the samples in a pin-on-disk wear test.

In this paper, the effect of mechanical vibration with reinforcement particles namely Silicon Carbide (SiC) on microstructure, mechanical properties, wear, and corrosion behaviors of aluminum alloy surface composites fabricated via friction stir processing (FSP) was investigated. The method was entitled friction stir vibration process (FSVP). The results revealed that recrystallized fine grains formed in all processing samples as a result of dynamic recovery and recrystallization, while samples processed in friction stir vibration processing resulted in better grain refinement in the stir zone than in conventional friction stir processing. Compared to conventional friction stir processing, in friction stir vibration processing, the hardness and tensile strength increased due to microstructure modification and better reinforcing distribution. From corrosion analysis, the corrosion resistance of the friction stir vibration processed samples showed a significant increase compared to the friction stir processed specimens. The wear results indicated that the wear resistance of friction stir vibration processed specimens is higher than friction stir processed specimens due to the development of smaller grains and a more homogenous distribution of the strengthening particles as the vibration is applied.

Various methods have been proposed to modify the friction stir welding. Friction stir vibration welding and underwater friction stir welding are two variants of this technique. In friction stir vibration welding, the adjoining workpieces are vibrated normal to the joint line while friction stir welding is carried out, while in underwater friction stir welding the friction stir welding process is performed underwater. The effects of these modified versions of friction stir welding on the microstructure and mechanical characteristics of AA6061-T6 aluminum alloy welded joints are analyzed and compared with the joints fabricated by conventional friction stir welding. The results indicate that grain size decreases from about 57 μm for friction stir welding to around 34 μm for friction stir vibration welding and about 23 μm for underwater friction stir welding. The results also confirm the evolution of Mg2Si precipitates during all processes. Friction stir vibration welding and underwater friction stir welding processes can effectively decrease the size and interparticle distance of precipitates. The strength and ductility of underwater friction stir welding and friction stir vibration welding processed samples are higher than those of the friction stir welding processed sample, and the highest strength and ductility are obtained for underwater friction stir welding processed samples. The underwater friction stir welding and friction stir vibration welding processed samples exhibit about 25% and 10% higher tensile strength compared to the friction stir welding processed sample, respectively. The results also indicate that higher compressive residual stresses are developed as underwater friction stir welding and friction stir vibration welding are applied.