Energetics of antiphase boundaries in γ′ Co3(Al,W)-based superalloys

James E. Saal*, C. Wolverton

*Corresponding author for this work

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Although Co-based superalloys are considered as a promising next-generation higherature turbine blade material, there are issues with regard to mechanical properties that must be addressed. L12 planar defects such as antiphase boundaries (APBs) play a critical role in the higherature strength of γ/γ′ superalloys, particularly with the magnitude and temperature-range of the yield strength anomaly. APBs in L12 Co3(Al,W) γ′ are particularly complex due to the presence of the metal mixing on the Al/W sublattice, which introduces additional degrees of freedom to APB behavior, such as Al/W composition and configuration local to the APB. We explore the behavior of APBs in L12 Co3(Al,W) with density functional theory. We find a strong dependence of the APB energy on the composition, particularly from the presence of Al-Al bonds across the 010 APB and W-W bonds across the 111 APB. For both APBs, our calculations also suggest an energetically favorable segregation of Al to the APB. Therefore, future Co alloy design criteria can include alloying elements with preferential segregation to the APB over that of Al to tune the APB energy (and the behavior of the yield strength anomaly). Furthermore, the unique behavior of Al-Al and W-W bonds in the 010 and 111 APB's, respectively, indicate the possibility of preferentially modifying one APB over another with alloying.

Original languageEnglish (US)
Pages (from-to)57-62
Number of pages6
JournalActa Materialia
Volume103
DOIs
StatePublished - Jan 15 2016

Keywords

  • Antiphase boundary
  • Cobalt-base superalloys
  • Density functional theory
  • L1

ASJC Scopus subject areas

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

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