Dislocation slip and twinning in Ni-based L12 type alloys

J. Wang, H. Sehitoglu

Research output: Contribution to journalArticlepeer-review

Abstract

We report theoretical results on dislocation slip and twinning in Ni 3 (Al, Ti, Ta, Hf) compositions with L12 crystal structures utilizing first-principles simulations. The lattice parameters of Ni3Al, Ni3Al0.75Ta0.25, Ni 3Al0.5Ta0.5, Ni3Ta, Ni3Ti and Ni3Al0.75Hf0.25 are calculated, and the crystal structures with lower structural energies are determined. We established the Generalized Stacking Fault Energy (GSFE) and Generalized Planar Fault Energy (GPFE), and calculated stacking fault energies APB (anti-phase boundary) and CSF (complex stacking fault) matched other calculations and experiments. Based on the extended Peierls-Nabarro model for slip and the proposed twin nucleation model, we predict slip and twinning stress and the results show a general agreement with available experimental data. The results show that in the studied intermetallic alloys, twinning stress is lower than slip stress; Ta and Hf ternary addition are substantial to increase flow stress in Ni 3Al. The models proposed in the paper provide quantitative understanding and guidelines for selecting optimal precipitate chemistry and composition to obtain higher mechanical strength in Shape Memory Alloys.

Original languageEnglish (US)
Pages (from-to)20-31
Number of pages12
JournalIntermetallics
Volume52
DOIs
StatePublished - Sep 2014

Keywords

  • A. Ternary alloy systems
  • D. Defects: dislocation geometry and arrangement
  • D. Defects: planar faults
  • E. Ab-initio calculations

ASJC Scopus subject areas

  • Chemistry(all)
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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