Influence of tool geometries and process variables on friction stir butt welding of Al-4.5%Cu/TiC in situ metal matrix composites

Present work describes friction stir welding of in-house produced and hot rolled Al-4.5%Cu/TiC in situ metal matrix composites by using hardened bimetallic tool with varying shoulder surface geometries and other process variables. Joining of the said composite using friction stir welding process has been seen to provide beneficial effects such as grain refinement of the matrix and subsequent redistribution and refinement of reinforcements. A predictive model has also been developed to estimate the weld properties such as tensile strength and ductility with respect to the tool geometry used and input process variables. The X-ray diffraction analysis results of Al-4.5%Cu/TiC butt welds indicated formation of CuAl2O4 and CuAl2 to some extent in the stir zone. Fractography of the weld samples revealed dimpled ductile nature of fracture. Through multi response optimization of the welding parameters and tool geometry, weld strength of 89% that of the base material was achieved.