First-principles simulations of plasticity in body-centered-cubic magnesium-lithium alloys

Ilgyou Shin, Emily A. Carter

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

First-principles quantum mechanics is an increasingly important tool for predicting material properties when designing novel alloys with optimized mechanical properties. In this study, we employ first-principles orbital-free density functional theory (OFDFT) to study plastic properties of body-centered-cubic (bcc) Mg-Li alloys as potential lightweight metals for use in, e.g., vehicle applications. The accuracy of the method as a predictive tool is benchmarked against the more accurate Kohn-Sham DFT (KSDFT). With a new analytic local electron-ion pseudopotential, OFDFT is shown to be comparable in accuracy to KSDFT with the conventional non-local pseudopotential for many properties of Mg-Li alloys, including lattice parameters and energy differences between phases. After this validation, we calculate generalized stacking fault energies (SFEs) of a perfect lattice and Peierls stresses (σ p's) for dislocation motion in various bcc Mg-Li alloys. Such predictions have not been made previously with any level of theory. Based on analysis of SFE barriers, we propose that alloys with 31-50 at.% Li will exhibit the greatest strength. Their σp's are predicted to be 0.18-0.31 GPa. The Li concentration in this range (31-50 at.%) has little impact on plastic properties of bcc Mg-Li alloys, while atomic-level disorder may decrease the σp. This range of σp is similar to the industrial goal for potential lightweight Mg alloys.

Original languageEnglish (US)
Pages (from-to)198-207
Number of pages10
JournalActa Materialia
Volume64
DOIs
StatePublished - Feb 1 2014

All Science Journal Classification (ASJC) codes

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

Keywords

  • Atomistic simulation
  • Density functional theory
  • Magnesium alloy
  • Peierls stress
  • Stacking-fault energy

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