Grain boundary characterization and energetics of superalloys

Michael D. Sangid, Huseyin Sehitoglu, Hans J. Maier, Thomas Niendorf

Research output: Contribution to journalArticlepeer-review

Abstract

In many engineering alloys, there exists a wide distribution of grain sizes; we investigate the role of grain boundaries as a strengthening mechanism in such a material. The coincidental site lattice (CSL) model is a powerful mathematical tool to characterize grain boundaries (GBs) and identify 'special' boundaries, which display beneficial mechanical behavior. We define the CSL and describe a detailed procedure to obtain this information from the grain orientation mapping via electron back scattering diffraction (EBSD). From this information, we show the evolution of the CSL for a nickel-based superalloy, Udimet 720 (U720), throughout various stages of processing (billet and forging) and experiments (tension, compression, and fatigue). A deeper level of understanding the GB's role in the mechanical behavior of the material is investigated through atomic simulations using molecular dynamics (MD) as the GB energy is determined for the most prevalent GBs within this material. The spatial map of the orientation and grain sizes measured from EBSD is linked to the GB energies calculated from MD. Based upon the large number of boundaries analyzed (29,035), there is a strong inverse correlation between GB energy and grain size for every specimen examined during the various processing and testing conditions.

Original languageEnglish (US)
Pages (from-to)7115-7125
Number of pages11
JournalMaterials Science and Engineering A
Volume527
Issue number26
DOIs
StatePublished - Oct 1 2010

Keywords

  • Coincidence site lattice (CSL)
  • Electron back scattering diffraction (EBSD)
  • Grain boundary energy
  • Molecular dynamics simulations
  • Nickel-based superalloys

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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