ABSTRACT
Friction stir welding is an emerging technique for welding similar and dissimilar materials with superior weld properties. Friction stir processing technology is an extension of friction stir welding for materials processing. The microstructure of the friction stir welding joint depends on the thermophysical properties of the base metal and heat generated during the process, which, in turn, depends on both process parameters and tool geometry. Compared to process parameters, computed fractal dimensions show a more definite trend with the ultimate tensile strength of the joints. The microstructure of the friction stir processing alloy revealed an absence of porosity, a very fine grained structure, and a uniform distribution of fine silicon particles. The friction stir processing of as-cast nickel–aluminum bronze materials provides microstructure refinement and homogenization as well as closure of porosity and improved mechanical properties. Superior tensile properties were obtained by optimizing both the shoulder diameter and tool rotational speed.
