EBSD with fine steps versus XRD in evaluating the density of statistically stored dislocations: comparison on cold rolled and annealed copper states

Orientation gradients evaluated by EBSD orientation mapping enable the assessment of dislocation structures in terms of the related crystal curvature; however, results of this popular approach strongly depend on the scanning step ratio to the dislocation spacing. Usually analyzed at a relatively large step, the measured curvature corresponds to the net Burgers vector of many local dislocations rather than individual defects. Accordingly, this method can estimate only the density of geometrically necessary dislocations (GND), which form agglomerations of the Burgers vector such as low-angle boundaries. At the same time, to reveal statistically stored dislocations (SSD), which alternate in sign and screen each other on their spacing scale, the scanning step should be essentially refined. As recently shown on low carbon bainitic steel, this uncommon expedient allows EBSD to measure the SSD density while avoiding limitations of the conventional TEM and XRD techniques. In this work, the considered novel method is applied at various recrystallization degrees of commercially pure copper, and the obtained results are compared to those by XRD. The comparison shows a satisfactory correlation between the estimates by two methods. Moreover, reference dislocation densities by EBSD for cold deformed and completely recrystallized states comply with the variation of local results over a partly recrystallized area.

1. Russian Science Foundation - project No 22 19 00627