12th International Conference on Magnesium Alloys and their Applications (Mg 2021): Mechanical Behaviors
Program Organizers: Alan Luo, Ohio State University; Mihriban Pekguleryuz, McGill University; Sean Agnew, University of Virginia; John Allison, University of Michigan; Karl Kainer; Eric Nyberg, Kaiser Aluminum Trentwood; Warren Poole, University of British Columbia; Kumar Sadayappan, CanmetMATERIALS; Bruce Williams, Canmetmaterials Natural Resources Canada; Stephen Yue, Mcgill University
Friday 9:50 AM
June 18, 2021
Room: Invited IV
Location: Virtual
Session Chair: Norbert Hort, Helmholtz-Zentrum Hereon
9:50 AM Invited
Design of Ductile Mg Alloys by Tuning Hard <c+a> Dislocations into Easy Ones: Bin Li1; Yidi Shen1; Qi An1; 1University of Nevada, Reno
Mg presents low strain to failure in c-axis compression, due to the fact that pyramidal dislocations, aka <c+a> dislocations, are hard to activate. Recent in-situ transmission electron microscopy study revealed that single crystal Mg could present very large plasticity (> 25%) in c-axis compression as a result of activation of high density, mobile <c+a> dislocations. It follows that if alloying elements that are able to lower the energy barrier to activating <c+a> dislocations can be identified, ductile Mg alloys can then be designed and processed. In this talk, we show that these alloying elements can be found by performing first principles high-throughput screening. In this approach, how alloying elements influence the generalized stacking fault energy on the pyramidal planes is calculated. Those elements that are able to reduce the unstable stacking fault energy, i.e. the energy barrier to dislocation nucleation and glide, are identified by combing through the Periodic Table.
10:20 AM Invited
The Indentation Size Effect in Mg Alloys: Warren Poole1; Shuheng Li1; Ghazal Nayyeri1; 1University of British Columbia
Instrumented indentation tests have received considerable recent attention for measuring the activity of slip systems in magnesium alloys. This approach has the advantage that single crystals are not required as tests can be conducted on polycrystalline samples. In this study, a range of magnesium alloys has been studied using instrumented indentation with a range of indenter tip radii from 1-250 μm. The indentation force-displacement curves were converted to indentation stress-strain curves using the approach of Kalidindi and co-workers. It was observed that there was a strong dependence of the indentation yield stress on the radius of indenter tip. A dislocation theory based model was developed to analyze the size effect. It was found that by extrapolating to an infinite indenter radius and calculating the resolved shear stress under the indenter, the critically resolved shear stress values obtained were in strong agreement with experimental results from single crystal.