Plastic strain-induced evolution of CSL boundaries at elevated temperature for Ni-base superalloy: Experimental and phase-field perspective

Samples cut from a 700°/322 MPa/9117 h creep-ruptured specimen as well as a non-tested sample were characterized by electron backscatter diffraction to investigate the evolution of low Σ (Σ≤29) coincident site lattice boundaries during strain at elevated temperature for Haynes 282 superalloy. Results show that the proportion of Σ3 boundaries, including Σ9 and Σ27 boundaries, decreases sharply with increasing strain. The two-mode phase-field crystal method is applied to simulate the dynamic evolution process of a Σ3 boundary. During deformation at _{^{ϵ´=5.62e-6}}, a twin embryo grows toward the initial Σ3 boundary with increasing strain and impinges onto it finally to form a Σ3-Σ3-Σ9 triple junction. In addition, part of the initial Σ3 boundary transforms into random grain boundary when the strain is large enough. Large numbers of dislocations are detected nearby Σ3 boundaries. They cause severe lattice rotations near Σ3 boundaries. In addition, some straight random boundaries can be found in strain zones only. Therefore, the transformation of Σ3 boundaries into random grain boundaries is the critical reason for the sharp decrease of Σ3 boundaries in strain zones.