Evaluating Deformation-Induced Grain Orientation Change in a Polycrystal During In Situ Tensile Deformation using EBSD

Abstract

Using an in situ load frame within a scanning electron microscope, a microstructural section on the surface of an annealed tantalum (Ta) polycrystalline specimen was mapped at successive tensile strain intervals, up to ~20% strain, using electron backscatter diffraction. A grain identification and correlation technique was developed for characterizing the evolving microstructure during loading. Presenting the correlated results builds on the reference orientation deviation (ROD) map concept where individual orientation measurements within a grain are compared with a reference orientation associated with that grain. In this case, individual orientation measurements in a deformed grain are measured relative to a reference orientation derived from the undeformed (initial) configuration rather than the current deformed configuration as has been done for previous ROD schemes. Using this technique helps reveal the evolution of crystallographic orientation gradients and development of deformation-induced substructure within grains. Although overall crystallographic texture evolved slowly during deformation, orientation spread within grains developed quickly. In some locations, misorientation relative to the original orientation of a grain exceeded 20° by 15% strain. The largest orientation changes often appeared near grain boundaries suggesting that these regions were preferred locations for the initial development of subgrains.

Identifying the microstructural features associated with void nucleation during elevated‐temperature deformation of copper

“…Conventional reference orientation deviation (ROD) is the misorientation between each point in a grain and some reference orientation, typically the average orientation of the grain at the same time step. However, following the technique introduced by Buchheit et al, 56 the reference orientation used in this study was the initial, undeformed, average orientation of the grain. To distinguish this from conventional ROD maps, the technique is notated here as uROD.…”

Predicting intragranular misorientation distributions in polycrystalline metals using the viscoplastic self-consistent formulation

“…At higher strains, certain grains in the VPFFT simulation will develop a quite large misorientation spread along the dominant rotation axis. Closer inspection reveals that the sign-carrying misorientation distribution along this direction is actually bimodal, which indicates that grain has fragmented into two parts [45,46]. By not considering the fragmented grains separately we have indirectly increased the values of equivalent isotropic spread.…”

Cold Gas Spraying of a High-Entropy CrFeNiMn Equiatomic Alloy

“…The band contrast is denoted as a gray scale from dark to light, indicating index quality from low to high, respectively. Higher degrees of deformation within the coating reduce the indexing quality of the IPF map significantly, which is shown as gray spots in the map [38]. Only 31% of points are indexed from the obtained map.…”