Environmentally-assisted grain boundary attack as a mechanism of embrittlement in a nickel-based superalloy

A. A.N. Németh, D. J. Crudden, D. E.J. Armstrong, D. M. Collins, K. Li, A. J. Wilkinson, C. R.M. Grovenor, R. C. Reed*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

56 Citations (Scopus)


The loss of ductility in the high strength polycrystalline superalloy 720Li is studied in air between room temperature and 1000 °C. Tensile ductility is influenced profoundly by the environment, leading to a pronounced minimum at 750 °C. A relationship between tensile ductility and oxidation kinetics is identified. The physical factors responsible for the ductility dip are established using energy-dispersive X-ray spectroscopy, nanoscale secondary ion mass spectrometry and the analysis of electron backscatter diffraction patterns. Embrittlement results from internal intergranular oxidation along the γ-grain boundaries, and in particular, at incoherent interfaces of the primary γ precipitates with the matrix phase. These fail under local microstresses arising from the accumulation of dislocations during slip-assisted grain boundary sliding. Above 850 °C, ductility is restored because the accumulation of dislocations at grain boundaries is no longer prevalent.

Original languageEnglish
Pages (from-to)361-371
Number of pages11
JournalActa Materialia
Publication statusPublished - 1 Mar 2017


  • Ductility minima
  • Environmentally-assisted cracking
  • Ni-based superalloy
  • Oxidation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys


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