The effect of thermo-mechanical processing on grain boundary character distribution in Incoloy 800H/HT

Abstract

In this study, we applied a thermo-mechanical process to alter the grain boundary characteristic distribution (GBCD) with a view to the feasibility of grain boundary engineering in Incoloy 800H/HT. In order to optimize the GBCD through increasing the low Σ coincidence-site lattice (CSL) boundaries, we applied various thickness reductions with two different rolling modes followed by annealing. We used Electron Backscattered Diffraction (EBSD) to analyze the GBCD and CSL boundaries. We found that the coincidence-site lattice boundaries, particularly Σ3 and its variants, increased with the pre-deformation level in cross-rolled (CR) samples. In contrast, the fraction of these CSL boundaries had an optimum in 50% reduction for unidirectionally rolled (UDR) samples. In fact, different Σ3n interactions led to different GBCD in UDR and CR processed samples. Low to medium deformation with UDR and medium to high deformation with CR on the Incoloy 800H/HT samples showed potential for grain boundary engineering.