Assessment of microstructure and mechanical properties of friction stir welded AA2014-O and AA2014-T6 sheets

Abstract

In this study, friction stir welding of AA2014-O and AA2014-T6 aluminum alloy was performed at various welding speeds to evaluate the in uence of temper conditions of base metal on the properties of the welded joints. The results showed strong in uence of base metal temper conditions on the microstructural morphologies and mechanical behavior of the welded joints. In the 2014-O joints, different zones of weld joint were diffused into each other and there was no clear interface between them. In 2014-T6 joints, there was a distinct demarcation between the NZ, TMAZ, HAZ and base metal. The welded joints in 2014-O temper condition showed increase in hardness in the vicinity of weld center due to grain re nement whereas, in 2014-T6, softening occurred in the same region by the dissolution of strengthening precipitates. The mechanical properties of 2014-O joints were equivalent to the base metal showing a 100% weld e ciency with fracture located in the base metal, whereas 2014-T6 welds exhibited about 70% weld e ciency with fracture located at the NZ/TMAZ interface. All the samples in mechanical testing fractured at retreating side (RS) which exhibited heterogeneity in the mechanical properties of the welded joints. SEM fractographic analysis revealed a ductile fracture mode comprising of dimples in both temper conditions. The size and shape of the dimples was strongly dependent on base metal temper condition.

Improvement in joint efficiency with high productivity and narrow weld formation in friction stir welding

“…The positive ideal solution (V + ) and the negative ideal solution (V − ) were computed using Eqn. (11) and Eqn. (12), respectively.…”

“…In the weld zone, these thermo-mechanical conditions result in a diversity of microstructures. 11 AA2219 and AA7475 pose the serious problem of solidification during welding by the fusion welding process. These Al alloys are extensively utilized in aerospace applications and thus an alternative joining process is required for successful joining of such alloys.…”