Misorientation distribution of high-angle boundaries formed by grain fragmentation: EBSD-based characterization and analysis performed on the heavily deformed iron

摘要

When studying crystal lattice fragmentation during plastic deformation of metals, it is of great importance to characterize high angle deformation-induced boundaries as long as their creation and evolution controls grain refinement. A problem exists however to separate a contribution of DIBs to overall misorientation distribution from a contribution of original grain boundaries, particularly when total lengths of high-angle deformation-induced and original grain boundaries are comparable. In the present study, a method making possible this separation based on electron backscattering diffraction is suggested and used to characterize evolution of deformation-induced boundary misorientations in polycrystalline iron deformed under various conditions. The method is shown to provide reasonable accuracy up to a strain of ~ 2 in the case of uniaxial compression and up to a strain of 5 in the case of multi-axial forging. It has been shown that character of the deformation-induced boundaries evolution in iron changes weakly when increasing deformation temperature from room temperature to 400°C. At the same time, this evolution differs significantly in iron deformed by uniaxial compression and multi-axial forging. In all cases considered in the present study a deformation-induced boundary misorientation distribution can be represented as a superposition of three partial distributions. The first two partial distributions correlate with those obtained earlier in transmission electron microscopy studies. The third partial distribution suggested in the present study describes the highest-angle part of deformation-induced boundary misorientation distribution. Each partial distribution evolves according to its own law with proceeding deformation.