Effect of thermomechanical processing on grain boundary character distribution of a Ni-based superalloy

Grain boundary engineering (GBE) was performed on an INCONEL alloy 617 by means of thermomechanical processing (TMP) to optimize the grain boundary character distribution (GBCD) with an increased fraction of low-Σ coincidence site lattice boundaries (CSLBs). Samples with a 5% thickness reduction followed by annealing at 1100 deg. C for 90 min promoted more low-Σ CSLBs than those with greater thickness reductions. The fraction of the Σ3n (Σ3, Σ9, and Σ27) boundaries was promoted preferentially by TMP, which is desirable for the improvement of material's properties. The thermal stability of the GBE-optimized GBCD was verified to be stable at 850 deg. C for 672 h without significant degradation