Effect of active heating and cooling on microstructure and mechanical properties of friction stir–welded dissimilar aluminium alloy and titanium butt joints

A butt joint configuration of AA6061–pure Ti was welded using friction stir welding (FSW) with an assisted cooling and heating conditions, aiming to attain a flawless joint. Cooling-assisted friction stir welding (CFSW) was carried out with a different cooling medium such as CO₂, compressed air and water at controlled flow rate. However, heating-assisted friction stir welding (HFSW) was performed with heating source of GTAW torch just before FSW tool at different current density. Prepared specimens were subjected to optical microscopy (OM), scanning electron microscopy (SEM) and electrodischarge spectroscopy (EDS) for microstructural characterizations. The tensile strength and microhardness were significantly affected by various cooling and heating conditions, attributing to the distinct proportion of the intermetallic compounds (IMCs) evident in the microstructure. The samples prepared with cooling conditions exhibited superior joint properties as compared with the normal and heating conditions. [Figure not available: see fulltext.].