Interface Structure and Energy Calculations for Carbide Precipitates in γ-TiAl

R. Benedek*, David N Seidman, C. Woodward

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations

Abstract

Ternary carbide precipitates improve the high-temperature creep strength of 2-phase TLAJ alloys. The perovskite (P-type) Ti3AlC nucleates at relatively low temperatures (750 deg. C), whereas hexagonal (H-type) Ti 2AlC precipitates occur at somewhat higher temperatures. Calculations are performed, based on first- principles-local-density-functional theory, of the interface structure and energy of these two carbides with a γ-TLAl matrix. Calculations are first done on coherent interfaces, and approximate corrections are then made for the effect of misfit. The perovskite is known to form needle-shaped precipitates oriented along the c-axis of the host. Our calculations yield a relatively low energy for the (100) perovskite-host interface, which is a favorable orientation owing to its low misfit, and because the terminating carbide layer for the coherent interface is pseudotnorphic with the host. Predictions are given for the critical thickness for coherence and the critical nucleation size for a P-type precipitate. Calculations for interfaces of H-type platelets with the host show a much larger interface energy than that for the P-type precipitate.

Original languageEnglish (US)
Pages (from-to)129-135
Number of pages7
JournalMaterials Research Society Symposium - Proceedings
Volume753
StatePublished - Nov 11 2003
EventDefect Properties and Related Phenomena in Intermetallic Alloys - Boston, MA, United States
Duration: Dec 3 2002Dec 5 2002

ASJC Scopus subject areas

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

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