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 language | English (US) |
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Pages (from-to) | 198-207 |
Number of pages | 10 |
Journal | Acta Materialia |
Volume | 64 |
DOIs | |
State | Published - Feb 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