Evolution of grain boundary character distributions in a cold-deformed Nickel-based superalloy during electropulsing treatment

The evolution of grain boundary character distribution in a cold-deformed nickel-based superalloy during the electropulsing treatment (EPT) was studied. The results revealed that both coherent Sigma 3 boundaries (Sigma 3(c)) and incoherent Sigma 3 boundaries (Sigma 3(ic)) were formed in the recrystallized structures mainly by growth accidents during EPT, while the fraction of Sigma 3(ic) boundaries became much lower at the higher EPT temperatures. Meanwhile, the fraction of Sigma 3 boundaries increased with the increasing EPT temperatures till 850 degrees C, and decreased again at 900 degrees C. In addition, the high mobility of grain boundary during EPT could promote the formation of stacking errors at some locations of high angle grain boundaries (HAGBs), and thus promoting the nucleation of annealing twins. With the increasing EPT time, the fraction of Sigma 3 boundaries increased slightly, and the unstable Sigma 3(ic) boundaries were transformed into stable Sigma 3(c) boundaries, in which intersecting migrating SRX fronts were easier to be extended. On the other hand, a lot of low-Sigma CSL grain boundaries were formed in the pre-deformed alloy with the strain of 0.1 during EPT, which was mainly attributed to the development of large grain-clusters. As the strain was large enough, the energy supplied by electropulsing could enable the cold-rolled alloy to effectively utilize the stored energy on the formation of Sigma 3 boundaries. Besides that, the evolution of Sigma 9 and Sigma 27 boundaries was analyzed in detail as well as the corrosion resistance of the studied alloy after different treatments. (C) 2020 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/).