Using transmission Kikuchi diffraction in a scanning electron microscope to quantify geometrically necessary dislocation density at the nanoscale

Highlights: • First report of using TKD to quantify GND at the nanoscale. • GND density has been measured in HAZ of a super duplex stainless steel sample. • Good agreement is found between TKD & TEM in identifying dislocation distribution. • TKD–GND method is an accurate, fast and accessible method for GND measurement. -- Abstract: It is challenging to quantify the geometrically necessary dislocation (GND) density at the nanoscale using conventional electron backscatter diffraction due to its limited spatial resolution. To overcome this problem, in this study, the transmission Kikuchi diffraction (TKD) technique is used to measure lattice orientation and to calculate the corresponding nanoscale GND density. Using the TKD method, a variation of GND density from 6 × 10¹⁴ to 10¹⁶ m⁻² has been measured in a welded super duplex stainless steel sample. The distribution of dislocation density is shown to be in good agreement with transmission electron microscope (TEM) result. Compared with dislocation measurements obtained by TEM, the TKD–GND method is revealed to be a relatively accurate, fast and accessible method.