Study on deviation distribution of Sigma 3 and Sigma 9 boundaries in Hastelloy C-276 superalloy with different hot rolling reductions

In this study, the deviation distributions of Sigma 3 and Sigma 9 grain boundaries in a Hastelloy C-276 sheet were measured using electron backscatter diffraction technology (EBSD) and the grain boundary plane orientation was analyzed using a five-parameter technique after hot rolling at 900 degrees C with different thickness reductions. The results show that the relative areas of Sigma 3 grain boundary planes reveal a strong peak at the (111) twist position, and the corresponding intensity significantly decreases as the reduction increases. The hot rolling generates dislocations, resulting in significant deviation of Sigma 3 grain boundary orientations and the loss of special properties. However, the Sigma 9 grain boundary plane distribution (GBPD) becomes more diffused with increasing deformation, and the multiples of random distribution (MRD) value is similar to 2. In addition, the large deviation of the Sigma 9 grain boundary orientation varies across the different strain samples. In low-strain samples, the deviation of the Sigma 9 grain boundary orientation may be affected by the Sigma 3 grain boundary deviation with construction of the Sigma 3-Sigma 3-Sigma 9 triple junction. The deformation microstructures mainly determine the deviation of the Sigma 9 grain boundary orientation in high-strain samples. Moreover, the distorted grain boundaries act as potent nucleation sites of dynamic recrystallization (DRX) during the hot rolling process. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).