Nugget zone characterization of friction stir welded hypereutectic Al-Si alloy

Despite excellent properties of aluminium silicon (Al-Si) alloys in several aircraft and automotive applications, its usage is limited because near net shape casting of Al-Si alloys may cause several defects like surface pinholes and grooves. Fabrication of components and then welding them via fusion-based welding processes imposes issues like porosity and slag inclusions which may severely degrades its properties. Thus in present study, friction stir welding (FSW) was employed for welding of hypereutectic Al-Si cast alloy. The nugget zone (NZ) of welded alloy and its as-cast counterparts were characterized for their performance in terms of mechanical and tribological behaviour. The results depicted fragmentation of alpha-Al dendrites, refinement and redistribution of acicular Si particles as a result of stirring with high strain rate, and improvement in mechanical properties such as ultimate tensile strength, yield strength, ductility, hardness and wear resistance as compared to as-cast alloy. It is also shown that disparate wear mechanisms occured in friction stir welded (FSWed) and as-cast alloys. A sizeable amount of adhesion with plastic deformation and delamination pits were observed for as-cast alloy, while the dominant mechanism in FSWed alloy was peeling with little adhesion.