Influence of tool pin profile on material flow, mechanical properties and corrosion behavior of friction stir welded dissimilar Al5083-6061

In the current investigation, dissimilar aluminum alloys (6 mm thick Al5083 and Al6061) joints were friction stir welded by three different kinds of tool geometries with varied pin features. The results indicated that the formation of the onion ring was confined to a small part of the stir region in the case of triangular pin profile (TP) and square pin profile (SP), whereas the whole stir zone was covered by onion ring or banded structure in case of taper threaded pin profile (TTP). TP and SP show better pulsating action and result in better shearing of the material, causing the material to mix in sideward directions from the advancing side to the retreating side. But, the essential upward and downward material flow to obtain uniform mixing of both base materials were observed in TTP. It contributed to better material flow, and the tool achieved better mechanical and corrosion properties. The hardness values of the joints welded with TP and SP showed uneven distribution in the stir zone, and using TTP could minimize the deviation in hardness values. The role of different tool geometries on material flow, microstructure, corrosion, and mechanical behavior was studied, and the result has been reported and described with detailed analysis.