Tensile Properties and Fusion Zone Hardening for GMAW and MIEA Welds of a 7075-T651 Aluminum Alloy

Tensile and hardness values for 7075-T651 aluminum alloy in the as welded and post weld heat treated conditions (solubilization and artificial aging-T6), obtained using GMAW and modified indirect electric arc (MIEA) welding processes are presented. Results showed that the base material along rolling direction exhibited a tensile strength of around 600 MPa and elongation of 11%. For the as welded condition, tensile strength was 260 MPa and elongation percent of 3%. This behavior was attributed to brittleness induced by the microstructural characteristics of the welded alloys, as well as high porosity. Hardness profiles along the welds were obtained and different welded zones were identified. A soft zone (similar to 100 HV0.1) in the heat affected zone for GMAW and MIEA was observed, the minimum hardness corresponding to weld metal (similar to 85 and similar to 96 HV0.1 for GMAW and MIEA, respectively). The high dilution between filler and base metal during welding in MIEA allows to the Zn and Cu to flow from the base metal into the weld metal, inducing hardening by solution and subsequent artificial aging. In this regard, the hardness of the weld metal for MIEA increases by 56%, while the tensile strength reaches a value close to 400 MPa. For GMAW, non-favorable hardening effect was observed for the weld metal after solution and artificial aging.