Mechanical properties of friction stir processed TIG-welded and friction stir welded 5083 aluminium alloy joints

Abstract

Material processing is all about improving the materials that already exist, discovering new ones, and finding original ways to use existing materials to produce high-quality, cost-effective parts and systems. It is very evident from day to day life that everyday technology keeps changing for better, to make life easier and simpler. As the technology keeps on evolving, manufacturers and designers will be at ease knowing that quality is not compromised. Friction stir processing is one of the new material processing techniques, derived from friction stir welding. The aim of this study was to characterize the mechanical behaviour of friction stir processed TIG welded 5083 aluminium plate and friction stir processed FSW 5083 aluminium plate as compared to unprocessed friction stir welded 5083 aluminium plate and TIG welded plate. Prior to the analysis of the plates, two 5083 aluminium alloy plates were welded using the two different welding techniques i.e. friction stir welding and Tungsten Inert Gas welding (TIG). The welded joints were then friction stir processed (FSP) using the parameters used during the FSW. The friction stir processed (or processed) joints were then cut and prepared for different analysis. This involved the tensile tests, bending tests, hardness tests, macrostructure and microstructure analysis. These analyses were performed so as to study the impact of applying the FSP on the previously mentioned joints (FSW and TIG welded joints). The unprocessed TIG welded joints were found to be the weakest joints amongst all the joints studied in this work. The processed FSW joints were found to be the strongest amongst the joints studied in this work. The characterized specimens were cut from different locations of the plates i.e. the beginning, the middle and the end of the plate. The specimens were also symbolized in a way representing their cut locations (A for the beginning, B for the middle and C for the end of the plate). This then suggests that each plate produced three specimens. It was noted that the behaviour of the unprocessed TIG welded joint was uniform along with the plate while the other joints vary with location. The specimens cut at the beginning of the plates were found to be weaker compared to the one cut in the middle and the end of the plates. This trend was noted on the processed TIG welded joints, unprocessed FSW and processed FSW welded joints. The results showed a clear distinction between processed joints and unprocessed joints. There was a good correlation observed between the microstructural results, bending and the tensile results. Refined grains were also observed on the microstructure of the processed weld joints. It was noticed that the hardness value of the processed joints was higher compared to that of the base material. The detailed correlation between the microstructure and the macrostructure is reported in the main text.