On the assessment of creep damage evolution in nickel-based superalloys through correlative HR-EBSD and cECCI studies

• Published in: Acta materialia Vol. 185; pp. 13 - 27
• Main Authors: Sulzer, Sabin, Li, Zhuangming, Zaefferer, Stefan, Hafez Haghighat, Seyed Masood, Wilkinson, Angus, Raabe, Dierk, Reed, Roger
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.02.2020
• Subjects: Creep damage; Discrete dislocation dynamics (DDD); Electron channelling contrast imaging (ECCI); High-resolution electron backscatter diffraction (HR-EBSD); Nickel-based single-crystal superalloys; High-resolution electron backscatter diffraction (HR-EBSD); Electron channelling contrast imaging (ECCI); Creep damage; Nickel-based single-crystal superalloys; Discrete dislocation dynamics (DDD)
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2019.07.018

The evolution of dislocation density with creep strain in single-crystal superalloys is studied quantitatively using high-resolution electron backscatter diffraction (HR-EBSD) and electron channelling contrast imaging under controlled diffraction conditions (cECCI). Data regarding dislocation density/structure is measured for deformation at 900 °C and 450 MPa up to  ≈  1% plastic strain. Effects of chemical composition are elucidated via three purpose-designed superalloys of differing rhenium and ruthenium contents. The evidence indicates that dislocation avalanching is already prevalent at plastic strains of  ≈  0.1%; thereafter, an exponential decay in the dislocation multiplication rate is indicative of self-hardening due to dislocation constriction within the matrix channels, as confirmed by the imaging. The results are rationalised using discrete dislocation dynamics modelling: a universal dislocation evolution law emerges, which will be useful for alloy design efforts. [Display omitted]