An investigation of post-weld heat treatment of friction stir welded aluminium blanks AA2024 embedded with AA7075

Abstract

Abstract This article is focused main problem during and after FSW especially when joining blanks AA2024 embedded with interlayer strip widths AA7075, in microstructure of the welded zone, that will in turn affect its mechanical properties of the welded joints. So, a number of interlock strip widths of AA7075 as 1, 1.5, 2, 2.5 and 3 mm were added between two substrates of base metal AA2024 during FSW technique then followed heating and cooling procedures to incorporate into the heat treatment process, which is conducted to create changes in a material’s microstructure that will in turn affect its mechanical properties. The analyses by optical microscope and scanning electron microscope were used to clarify microstructural characterization of FSWed with interlock strip widths after PWHTed. On the other hand, the microhardness and tensile tests were performed to determine mechanical properties of FSWed with interlock strip widths after PWHTed. The observations of microstructural elucidated that the good bonding connection between interlayer strip widths AA7075 and base metal AA2024 was due to use the procedures of PWHT. The mechanical properties such as microhardness and tensile of produced joints with PWHTed were showed higher than without PWHTed. Specifically, the ultimate tensile strength, and hardness values of the post-heat joint when using 3mm interlayer strip were obtained the highest values 299MPa, 186 HV respectively. This presents improvement by 11.2% in tensile strength, and 84% in hardness, compared to as weld joint.