Orientation-dependence of incipient plasticity in a coarse-grained Mg revealed by nanoindentation pop-ins
Bibliographic record
Abstract
• We employed nanoindentation across a broad spectrum of crystallographic orientations in a Mg-2wt% Gd alloy to elucidate the influence of orientation on the onset of plasticity, i.e., pop-in events. • We demonstrated orientation-dependent pop-in events in a Mg alloy, providing new insights into how various slip systems—including basal 〈a〉, prismatic 〈a〉, and pyramidal 〈c + a〉—activate to induce incipient plasticity within different grains. • We reported a successive pop-in phenomenon, for the first time in Mg, in grains near (0001) orientations, which we attribute to the formation of basal-pyramidal dislocation locks. The nanoindentation pop-in behaviors of 13 grains with diverse crystallographic orientations were analysed using a coarse-grained Mg-2 wt.% Gd alloy. Within nanoscale stressed volumes within all grains, the converted shear stresses for the first pop-in, calculated using the indentation Schmid factor, ranged from 1 to 1.3 GPa, consistent with theoretical predictions for dislocation nucleation in Mg. The estimated activation volume of the first pop-in was approximately 27–40 ų (involving about ∼2 atoms), aligning with reported atomistic simulations of the surface dislocation semi-loop nucleation. While indented near the ⟨c⟩-axis, grains exhibit higher first pop-in loads and successive pop-ins, implying the possibility of a cross-slip nucleation mechanism to accommodate ⟨c⟩-axis deformation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".