Abstract
We employ a free energy density for Mg–Al alloys that is dependent on concentration, strain, and temperature, and derived from quantum mechanical calculations by Ghosh & Bhattacharya (Acta Mater 193:28–39, 2020) , to model the dynamic precipitation of the Mg17Al12 phase during creep experiments in Mg–Al alloys. Our calculations show that the overall volume fraction of the dynamically formed precipitates is influenced by stress, and furthermore, this influence is anisotropic and asymmetric. Specifically, when the stress is volumetric or along the c-axis direction, the volume fraction of the precipitate phase is greater in compression and lower in tension. Surprisingly, stress along the a- or b-axis directions does not alter the volume fraction of the precipitates. The resistance to creep is improved by the presence of finely dispersed precipitates with a small aspect ratio, closer to spherical or ellipsoidal in shape and high number density. A greater volume fraction of these fine particles are produced during compressive creep tests than tensile creep experiments and thereby explaining the higher creep rate observed in tension than in compression in these alloys. Overall, our calculations explain the tension–compression asymmetry of the creep rate observed in creep experiments in Mg–Al alloys (Agnew et al. in Magn Technol 2000:285–290, 2000; Agnew et al. in Magn. Alloys Appl. 685–692, 2000).
| Original language | English |
|---|---|
| Pages (from-to) | 2363-2374 |
| Number of pages | 12 |
| Journal | Continuum Mechanics and Thermodynamics |
| Volume | 33 |
| Issue number | 6 |
| DOIs | |
| State | Published - Nov 2021 |
Funding
I would like to thank Professor Kaushik Bhattacharya (California Institute of Technology) for his mentorship. I would like to acknowledge Professor Sean Agnew (University of Virginia) for bringing to my notice the experimental work related to the asymmetric creep performance of Magnesium–Aluminum alloys. I also thank the anonymous reviewers for their valuable comments and suggestions. Part of this research was performed when I had held a position at the California Institute of Technology. I gratefully acknowledge funding in part from the Army Research Laboratory under Cooperative Agreement Number W911NF-12-2-0022. Some of the computations were conducted in the Resnick High Performance Center, a facility supported by Resnick Sustainability Institute at the California Institute of Technology. This research used resources of the Oak Ridge Leadership Computing Facility, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory under contract DE-AC05-00OR22725. This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). I would like to thank Professor Kaushik Bhattacharya (California Institute of Technology) for his mentorship. I would like to acknowledge Professor Sean Agnew (University of Virginia) for bringing to my notice the experimental work related to the asymmetric creep performance of Magnesium?Aluminum alloys. I also thank the anonymous reviewers for their valuable comments and suggestions. Part of this research was performed when I had held a position at the California Institute of Technology. I gratefully acknowledge funding in part from the Army Research Laboratory under Cooperative Agreement Number W911NF-12-2-0022. Some of the computations were conducted in the Resnick High Performance Center, a facility supported by Resnick Sustainability Institute at the California Institute of Technology. This research used resources of the Oak Ridge Leadership Computing Facility, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory under contract DE-AC05-00OR22725.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Office of Science | |
| Oak Ridge National Laboratory | DE-AC05-00OR22725 |
| Army Research Laboratory | W911NF-12-2-0022 |
| California Institute of Technology | |
| Resnick Sustainability Institute for Science, Energy and Sustainability, California Institute of Technology | |
| University of Virginia |
Keywords
- Anisotropy
- Creep
- First-principles
- Free-energy
- Magnesium alloys
- Precipitation