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

Abstract

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 ∑ (∑≤29) coincident site lattice boundaries during strain at elevated temperature for Haynes 282 superalloy. Results show that the proportion of ∑3 boundaries, including ∑9 and ∑27 boundaries, decreases sharply with increasing strain. The two-mode phase-field crystal method is applied to simulate the dynamic evolution process of a ∑3 boundary. During deformation at ε´=5.62e-6, a twin embryo grows toward the initial ∑3 boundary with increasing strain and impinges onto it finally to form a ∑3-∑3-∑9 triple junction. In addition, part of the initial ∑3 boundary transforms into random grain boundary when the strain is large enough. Large numbers of dislocations are detected nearby ∑3 boundaries. They cause severe lattice rotations near ∑3 boundaries. In addition, some straight random boundaries can be found in strain zones only. Therefore, the transformation of ∑3 boundaries into random grain boundaries is the critical reason for the sharp decrease of ∑3 boundaries in strain zones. Keywords: Ni-base superalloy, Strain, Coincident site lattice, Phase-field model