In situ neutron diffraction analysis of grain structure during friction stir processing of an aluminum alloy

Significant neutron peak broadening was observed in situ underneath the tool of friction stir processing (FSP) in 6061-T6 aluminum alloy. Such broadening was correlated to the dislocation density and subgrain size by using peak profile analysis methods. The high dislocation density of about 1.3×1015 m−2 underneath the FSP tool sharply decreases to 1.0×1014 m−2 outside the tool. The quantitative determination is consistent with the high-resolution x-ray and TEM results.

► In situ neutron diffraction method was applied to determine the transient grain structure.
► The dislocation density and subgrain size were quantified using peak profile analysis.
► The dislocation density of 1.3×1015 m−2 was measured underneath the tool under processing.
► The results are consistent with the high-resolution x-ray and TEM observations.