EBSD analysis of grain-refinement mechanisms operating during equal-channel angular pressing of commercial-purity titanium

Electron backscatter diffraction was applied to examine the fundamental mechanisms governing the development of ultrafine-grain microstructures during equal-channel angular pressing of commercial purity titanium. Texture analysis and examination of misorientation distributions revealed the enhanced activity of non-prismatic slip systems at prior grain boundaries, which promoted the preferential development of deformation-induced boundaries in these areas. By contrast, deformation in the interior of grains was dominated by prism slip which resulted in sluggish microstructural evolution. This difference in slip activity gave rise to the preferential nucleation of ultrafine grains at prior grain boundaries and thus the development of a bimodal grain structure. The grain refinement was concluded to result primarily from the incompatibility of deformation in neighboring grains. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.