Generalized stacking fault energies of Cr23C6 carbide: A first-principles study.

Graphical abstract Highlights • The GSFE of Cr 23 C 6 were calculated in prominent slip systems, for the first time. • Different to simple fcc structures, Cr 23 C 6 shows a double bell-shaped GSFE curve. • GSFEs of two slip systems revealed that {1 1 1}〈 1 1 2 ¯ 〉 is the most favorable system. • Electronic configuration alternation near slip planes govern the stacking behavior. Abstract In many high temperature-resistant Ni-based superalloys, M 23 C 6 carbides form during processing and remain as non-metallic inclusions during the materials use in application. M 23 C 6 type inclusions are principal sites for potential fatigue crack initiation, thus the accurate quantification of their energy barriers for deformation is necessary for in-depth understanding of the overarching mechanical behavior of the material system. In this study, the generalized stacking fault energies (GSFE) are theoretically determined for chromium-rich types of M 23 C 6 carbides (i.e. , Cr 23 C 6) in two prominent slip systems: {1 1 1}〈 1 1 2 ¯ 〉 and {1 1 1}〈 1 0 1 ¯ 〉. The results present GSFE curves with double saddle points in both slip systems. The double saddle points of the GSFE curves are explained via the electronic structure of atoms near the slip plane. At deformation quantified by half of a Burgers vector (i.e. , 0.5 b p), a pentacyclic charge density distribution appears representing a local minimum energy configuration, which results in a valley of the GSFE curve. Furthermore, the effective coordination number (n) and the distortion index (Δ d) of the coordination polyhedrons are employed to characterize the structural change. The analysis reveals that the values of the indexes n and Δ d at a displacement value of 0.5 b p are close to the values of a perfect Cr 23 C 6 crystal, while comparatively the distortion index is higher at the saddle points. These results provide new insights into the deformation pathways of M 23 C 6 carbides. [ABSTRACT FROM AUTHOR]