Effect of water quenching into strength, hardness and microstructure of the welded AA 6061 plates

Purpose The purpose of this study is to find the effect of heat treatment on the mechanical proeprties of aluminum. Aluminum exhibits a good response to heat treatment, especially quenching, according to the mechanical property improvement. The presence and orientation of secondary phases (Al-Fe-Mn-Si) are greatly affected by the quenching process. Design/methodology/approach The present work deals with the effect of water quenching on the mechanical properties of welded AA 6061 plates which were joined by using metal inert gas (MIG) welding, tungsten inert gas welding and friction stir welding (FSW). Three tests like tensile, bending and hardness were considered. The microstructural variation was analyzed by optical microscopy and elemental mapping through field emission scanning electron microscope. Findings A significant enhancement in the tensile strength and hardness was achieved on postquenched specimens. This improvement in mechanical properties is caused by the distribution of fine alloying elements throughout the metal solution rather than precipitation at the grain boundaries. In comparison to the “untreated specimens,” an improvement of 76.7%, 25.32% and 56.81% in the tensile strength of quenched TIGW, MIGW and FSW specimens, respectively, was observed. Originality/value The quenching process has increased the strength of the MIG welded joint over the base metal. The MIG welded joint has a larger flexural modulus than the other two welded plates, according to the results of the bending test. Furthermore, a uniform distribution of hardness was observed in postquenched welded specimens. It was found that welded zone was harder than heat-affected zone. Out of all the specimens, the base metal zone has the lowest hardness.