Relationship between welding conditions, abnormal grain growth and mechanical performance in friction-stir welded 6061-T6 aluminum alloy

In this work, a relationship between welding conditions, annealing behavior, and mechanical performance of friction-stir welded (FSWed) 6061-T6 aluminum alloy was examined. In the entire studied FSW range, the welded material was found to be unstable against abnormal grain growth during post-weld solutionizing treatment. However, a lowering of the FSW heat input tended to inhibit this undesirable phenomenon. In addition to the stir zone, the abnormal microstructural coarsening was also observed in the heat-affected zone, whereas the thermo-mechanically affected zone experienced static recrystallization. In all cases, the abnormal grain growth was found to result in similar to 25-35 degrees <110> rotation of the original crystallographic texture. Hence, this process was suggested to be governed by the orientation-growth mechanism. Due to the relatively high strain-hardening ability intrinsic to the coarse-grained materials, the abnormal grains suppressed tensile strain in the stir zone during transverse tensile tests thus degrading weld ductility.

Automated summary

The relationship between welding conditions, annealing behavior, and mechanical performance of friction-stir welded 6061-T6 aluminum alloy was examined in this study. It was found that the welded material was unstable against abnormal grain growth during post-weld solutionizing treatment, with a lowering of FSW heat input inhibiting this phenomenon. Abnormal grain growth was observed to lead to a rotation of the original crystallographic texture, and may be governed by the orientation-growth mechanism.