Formability limits and fracture mechanisms in AA5182 Al-Mg sheets under room and cryogenic temperature conditions
Bibliographic record
Abstract
The formability of in-demand Al-Mg alloys, such as AA5182, is constrained by the Portevin-Le Chatelier (PLC) effect, which manifests as serrated plastic flow due to dynamic strain aging (DSA) from solute-dislocation interactions. This phenomenon contributes to the premature onset of necking (i.e., reduced ductility) and surface defects, hindering the broader application of these alloys in lightweight structural components. The formability limits and fracture mechanisms for AA5182 sheets subjected to uniaxial tension and Erichsen punch forming were investigated under room temperature (293 K) and cryogenic (77 K) conditions. The cryogenic tensile fracture strain and flow stress increased by 47 % and 91 %, respectively, the Considère necking criterion was globally satisfied and surface wrinkling was fully prevented. Cryogenic forming limit diagrams (FLDs) were obtained for the first time for AA5182 sheet material using the Erichsen punch tests. The major strain limits increased by 18 %, 43 % and 27 % for uniaxial (drawing), plane strain and biaxial stretching strain paths, respectively, compared to room temperature conditions. Optical microscopy of the through-thickness microstructure confirmed that PLC suppression at 77 K prevented unstable interactions with opposing shear planes, promoting more uniform strain distribution and sheet thinning. Scanning electron microscopy of the fractured edges revealed a higher frequency of dimple initiation sites and 29 % greater dimpled area post-forming under cryogenic conditions due to delayed fracture and correspondingly increased void formation and growth. The average post-forming surface roughness was also reduced (improved) by a factor of 5, representing the difference between Class B and Class A surface finishes. • First complete cryogenic forming limit diagrams (FLDs) at 77 K for AA5182 sheets. • Major strain limits from cryogenic, 77 K FLD increased up to 42 % compared to 293 K. • Portevin-Le Chatelier (PLC) bands suppressed; fracture delayed for cryogenic tests. • More even sheet thinning at 77 K since opposing PLC and shear planes were avoided. • Strain marks eliminated and post-forming surface roughness improved 400 % at 77 K.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".