Orientation and deformation conditions dependence of dislocation substructures in cold deformed pure tantalum

Abstract

The evolution of dislocation arrangement during deformation can lead to the development of dislocation substructures which have direct consequences on the subsequent microstructural evolutions. Dislocation densities and substructures of various deformed microstructures of pure tantalum are analyzed in order to study the influence of deformation conditions. Electron BackScatter Diffraction (EBSD) and Electron Channeling Contrast Imaging (ECCI) are used in order to characterize the development of dislocation substructures. Investigation at grain scale shows the orientation dependence of the deformed state with the highest dislocation content for γ-fiber grains. This fiber appears to be quite stable in compression but less in rolling. Investigation at dislocation substructure scale highlights the influence of orientation on dislocation substructure forming. Developed substructures are present in the interior of γ-fiber grains. The evolution of the disorientation and size of substructures with strain depends greatly on the initial fraction of γ-fiber in the microstructure. Models describing these evolutions are proposed for γ-fiber grains. On the basis of the present analysis it is concluded that dislocation density parameter does not allow transcribing the differences of substructural development.