Effect of Intermetallic Compounds on Mechanical and Microstructural Properties of Dissimilar Alloys Al-7Si/AZ91D

AZ91D (Mg alloy) and A356 (Al-7Si) were fabricated by friction stir welding (FSW) at different process parameters, affecting the welded joints` mechanical properties. The results demonstrated that preferred properties were observed when AZ91D was placed on the advancing side. Mechanical properties, microstructure, elemental mapping, and fractography were analyzed by optical microscopy (OM), scanning microscopy (SEM), and energy-dispersive x-ray spectrograph, etc. The primary Al and Mg diffraction peaks were present, and Al12Mg17 and Al3Mg2 were intermetallic in all of these joints. This occurred due to the inter-diffusion performance of Al and Mg atoms in the welding and formed intermetallic compounds. The Al12Mg17 phase mixed with the Mg phase has preferentially lowered to the weld surface where the AZ91D plate was placed, and legitimate liquation may occur and be observed in the eutectic microstructures. The maximum ultimate tensile strength (UTS) of 90.57 MPa was perceived at tool rotational speed (TRS) of 900 rev/min with a traverse speed (TS) of 100 mm min−1, and the lower UTS (76.63 MPa) was found at TRS of 700 mm min−1.