Eutectic Segregation and Cracking in AZ91 Friction Stir Spot Welds
Bibliographic record
Abstract
<div class="htmlview paragraph">Friction stir spot welding of Mg-alloy AZ91 is investigated. The temperature cycles within the stir zone and in the TMAZ region are examined using thermocouples, which are located within the tool itself and also by locating thermocouples in drilled holes at specific locations relative to the bottom of the tool shoulder and the periphery of the rotating pin. The measured temperatures in the stir zone range from 437°C to 460°C (0.98T<sub>s</sub>, where T<sub>s</sub> is the solidus temperature in degrees Kelvin) in AZ91 spot welds produced using plunge rates from 2.5 and 25 mm/s.</div> <div class="htmlview paragraph">The thermal cycle within the stir zone formed during AZ91 spot welding could not be measured by locating thermocouples within the workpiece in drilled holes adjacent to the periphery of the rotating pin. It is suggested that the drilled holes containing the thermocouples are displaced both laterally and downwards as a result of the helical vertical rotational flow, which is created within the stir zone during the dwell period in spot welding.</div> <div class="htmlview paragraph">The stir zone microstructures in AZ91 spot welds typically comprise fine equiaxed α-Mg grains. However, spot welds produced with or without the introduction of a thermal insulating layer between the bottom of the AZ91 test section and the upper surface of the steel anvil show evidence of liquid penetration, eutectic segregation and cracking in the locations close to the stir zone extremities. Cracking is also observed in the TMAZ region of spot welds produced with a thermal insulating layer between the bottom of the AZ91 sections and the upper surface of the steel anvil.</div>
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| 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".