Influence of welding parameters on stir zone microstructures during friction stir welding of magnesium alloys
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Bibliographic record
Abstract
The microstructural features produced in friction stir welded AZ31, AZ80 and AZ91 alloys are examined using a combination of optical and scanning electron microscopy. The influences of tool rotation speed and travel speed are examined in terms of the stir zone phases and grain structures in the three base materials which contained different levels of Mg17Al12 phase. The microstructures primarily consist of α-Mg grains with α-Mg+Mg17Al12 colonies; however, melted films of Mg17Al12 are produced in AZ91 alloy when high rotation speeds are applied. When the rotation speeds are slow, or the travel speeds are fast, the Mg17Al12 was incorporated into the stir zone; however, they do not exhibit an elongated lamellar morphology associated with melted films. In the case of AZ80, the extruded base material contains a smaller fraction of Mg17Al12 and few of these phases are observed in the stir zones, while the AZ31 microstructure before and after welding remained as primary Mg grains. The results are explained based on the dissolution rate and melting temperatures of Mg17Al12 controlling the overall morphology and fraction of phases in the stir zone.On examine les caractéristiques des microstructures, produites dans les alliages AZ31, AZ80 et AZ91 soudés par friction-malaxage, en utilisant une combinaison de microscopie optique et de microscopie électronique à balayage. On examine l’influence de la vitesse de rotation de l’outil et de la vitesse de déplacement par rapport aux phases de la zone de malaxage et de la structure de grain des trois matériaux de base, qui contenaient des niveaux différents de la phase Mg17Al12. Les microstructures consistent principalement en grains de Mg-α avec colonies de MgzMg17Al12-α; cependant, des films fondus de Mg17Al12 sont produits dans l’alliage AZ91 lorsqu’on applique de grandes vitesses de rotation. Lorsque la vitesse de rotation est lente, ou que la vitesse de déplacement est rapide, le Mg17Al12 était incorporé dans la zone de malaxage; cependant, ils n’exhibent pas la morphologie lamellaire allongée associée aux films fondus. Dans le cas du AZ80, le matériau de base extrudé contient une plus petite fraction de Mg17Al12 et l’on observe peu de ces phases dans les zones de malaxage, alors que la microstructure du AZ31, avant et aprés le soudage, reste sous forme de grains primaires de Mg. On explique les résultats en se basant sur la vitesse de dissolution et les températures de fusion de Mg17Al12 contrôlant la morphologie globale et la fraction des phases dans la zone de malaxage.
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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 |
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