Improving the properties of friction stir welded 2219-T87 aluminum alloy with GTA offset preheating

The 2219 aluminum alloy was used more and more widely recently due to the excellent properties. The gas tungsten arc preheating at the advancing side was used to investigate the microstructure and the properties of the friction stir welded joints. The results show that the mechanical properties of the friction stir welds were enhanced with arc preheating. The tensile strength was increased by 12.3 % with the difference of the hardness between the advancing side and retreating side was reduced with preheating at the advancing side. It’s mainly because the fluidity of the material at the advancing side was improved significantly and so the drastic microstructure transform was effectively reduced at the advancing side. Meanwhile, the distribution of grain size from nugget zone to the advancing side was more gradual with the extra heat added to the hybrid friction stir welds than that in conventional friction stir welds. Furthermore, the high angle grain boundaries at the transition zone of preheated friction stir welds were higher, while the texture strength was lower than that of conventional friction stir welds, indicating that the dynamic recrystallization at the advancing side was sufficient with preheating.