The significance of Al-Si alloys lies in their exceptional mechanical properties and corrosion resistance, rendering them a notable category of technological materials. They are particularly emphasized in the automotive component manufacturing industry. Friction stir welding proved to be one of the most favorable methods to overcome the inherent problems regard-ing fusion welding of aluminum alloy encompassing cold cracking defects and porosity. This work focuses on the weldability of the AlSi9Cu3 through friction stir welding and different combinations of lap-joint welding of high-pressure die-cast and sand-cast AlSi9Cu3 as well as plate extrusion Al 6063-T6. The feasibility of the friction stir welding of the abovemen-tioned alloys has been accomplished, and the set of 1500 RPM and 6000 N as the rotation speed and axial force, in combination with the welding speed of 5 mm/s and tilt angle of one degree, have been selected as the optimum set of parameters for achieving a defect-free weld. Moreover, the hardness of the defect-free welds were measured, and the result depicted a consistency in the hardness through the whole cross-section of the weld.