Lower-bound dislocation density mapping in microcoined tantalum using high-resolution electron backscatter diffraction

摘要

High-resolution electron backscatter diffraction (HR-EBSD) is used to map the geometrically necessary dislocation (GND) density in the cross-sections of annealed, rolled, and microcoined tantalum foils that are typical targets used in modern laser-induced compression materials science studies. The microcoined samples are characteristic of microforming, where the deformation length scale is on the order of the grain size (similar to 50 mu m). In particular, inhomogeneities in dislocation density maps across 0.1-1 mm regions of interest are compared with expectations from slip line field approximations. The average HR-EBSD GND dislocation density measurements in various annealed and cold worked tantalum samples are compared with corresponding dislocation density approximations from microhardness measurements. GND densities in the range 10(13) - 10(15) m(-2) are typical.