High-resolution electron microscopy of dislocation ribbons in a CMSX-4 superalloy single crystal

V. A. Vorontsov, L. Kovarik, M. J. Mills, C. M.F. Rae

Research output: Contribution to journalArticle

54 Citations (Scopus)

Abstract

High-resolution scanning transmission electron microscopy (STEM) has been used to study the structure of dislocations in single crystal superalloy samples that have been subjected to conditions that favour the primary creep regime. The study has revealed the detailed structure of extended a2〈112〉 dislocations as they shear the γ′ precipitates during creep. These dislocations dissociate in a manner that is consistent with predictions made using the phase-field model of dislocations and also suggests the importance of the reordering process during their movement. The shearing done by the a〈1 1 2〉 dislocations was also found to distort the γ/γ′ interface, changing its appearance from linear to a "saw tooth" pattern. Another important observation was the segregation of alloying elements with a high atomic mass to the stacking faults, presumably to reduce their energies during shear. Numerous a2〈110〉 dissociated dislocations were also observed in the γ channels of the superalloy. The high resolution provided by the STEM imaging enables one to study the high-energy faults that are usually difficult to observe in conventional weak-beam TEM, such as complex intrinsic and extrinsic stacking faults in the γ′ and intrinsic stacking faults in the γ, and to make estimates of their energies.

LanguageEnglish
Pages4866-4878
Number of pages13
JournalActa Materialia
Volume60
Issue number12
DOIs
Publication statusPublished - 1 Jul 2012

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High resolution electron microscopy
Stacking faults
Dislocations (crystals)
Superalloys
Single crystals
Transmission electron microscopy
Creep
Scanning electron microscopy
Alloying elements
Shearing
Precipitates
Imaging techniques

Keywords

  • dislocation dissociation
  • primary creep
  • shockley partials
  • stacking faults
  • STEM

Cite this

Vorontsov, V. A. ; Kovarik, L. ; Mills, M. J. ; Rae, C. M.F. / High-resolution electron microscopy of dislocation ribbons in a CMSX-4 superalloy single crystal. In: Acta Materialia. 2012 ; Vol. 60, No. 12. pp. 4866-4878.
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High-resolution electron microscopy of dislocation ribbons in a CMSX-4 superalloy single crystal. / Vorontsov, V. A.; Kovarik, L.; Mills, M. J.; Rae, C. M.F.

In: Acta Materialia, Vol. 60, No. 12, 01.07.2012, p. 4866-4878.

Research output: Contribution to journalArticle

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