The mechanical properties of the GMAW, GTAW and FSW joints of the RDE-40 aluminium alloy

Abstract

The present study is concerned with the effect of welding processes on the mechanical properties of the RDE-40 aluminium alloy, closely confirming with the AA7039 (Al-Zn-Mg) alloy. The frequently preferred welding processes for this alloy are Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW) due to their comparatively easier applicability and better economy. In this alloy, the weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results in inferior weld mechanical properties and poor resistance to hot cracking. Friction Stir Welding (FSW) is an innovative solid-phase welding technique that was developed primarily for welding metals and alloys that heretofore have been difficult to weld using more traditional fusion techniques. In the present work, the tensile properties, microhardness, microstructure and fracture surface morphology of the GMAW, GTAW and FSW joints are evaluated and results are compared. From this investigation, it is found that the FSW joints of the RDE-40 aluminium alloy shows superior mechanical properties compared with the GTAW and GMAW joints and this is mainly due to the formation of a very fine, equiaxed microstructure in the weld zone.