Influences of post-weld artificial aging on microstructural and tensile properties of friction stir-welded Al-Zn-Mg-Si-Cu aluminum alloy joints

Abstract

In this study, the effect of heat treatment on the mechanical and microstructural properties of welded joints after friction stir welding of age-hardenable Al-Zn-Mg-Si-Cu wrought aluminum alloy plates was investigated. For this purpose, some of the samples welded using FSW technique with a rotational speed of 1250 rpm and a traverse speed of 40 mm·min-1 were subjected to annealing and some to artificial aging heat treatment at different temperatures and times. In FSWed artificial aged samples where AlFeSi precipitate formations were detected, hardness and strength increase were realized with grain-boundary strengthening and Orowan hardening mechanisms. The lowest ultimate tensile strength was 156.3 N·mm-2 in the annealed sample, while the highest ultimate tensile strength was 210.8 N·mm-2 in the sample artificially aged at 190 °C for 2 hours. Fractographic examination revealed that ductile fracture occurred in all specimens.