Grain structure and dislocation density measurements in a friction-stir welded aluminum alloy using X-ray peak profile analysis

The dislocation density and grain structure of a friction-stir welded 6061-T6 aluminum alloy were determined as a function of distance from the weld centerline using high-resolution micro-beam X-ray diffraction. The results of the X-ray peak profile analysis show that the dislocation density is about 1.2 × 1014 m−2 inside and 4.8 × 1014 m−2 outside of the weld region. The average subgrain size is about 180 nm in both regions. Compared to the base material, the dislocation density was significantly decreased in the dynamic recrystallized zone of the friction-stir welds, which is in good correlation with the TEM observations. The influence of the dislocation density on the strain hardening behavior during tensile deformation is also discussed.