Plastic Deformation and Surface Damage Mechanisms during Hot-forming of Al and Mg Alloy Sheets
Notice bibliographique
Résumé
Material transfer and adhesion to die surface are major tribological issues encountered during hot-forming of aluminum and magnesium alloys, reducing process efficiency. This study aimed at understanding the tribological contact interface generated between material and die surface under dynamic conditions created by simultaneous effect of temperature and strain rate. Micromechanisms of plastic deformation occurring under simulated hot-forming conditions were identified and related to the coefficient of friction (COF). Sliding contact experiments were done using specially designed tribometer (operating temperature: 25 to 545°C, strain rate: 10\n-3\nto 10\n-1\ns\n-1\n). COF of AA5083(Al-4.5%Mg-0.7%Mn) and AZ31(Mg-3%Al-0.7%Zn) alloys were measured during their plastic deformation by the simultaneous effect of temperature and strain rate. The as received and plastically deformed surfaces were characterized using optical interferometry, SEM, FIB and TEM. Additionally, the force required to break the asperity junction formed at the first contact, or junction strength, was measured for both materials at different temperatures. Deformation mechanisms identified for AA5083 in the temperature range of 420 to 545°C and strain rate range of 5×10\n-3\nto 4×10\n-2\ns\n-1\nincluded diffusional flow, grain boundary sliding (GBS) and solute drag (SD) creep. Friction maps outlining general relationships between tribological behaviour and micromechanisms controlling deformation under a set of temperature, strain and strain rate were developed. GBS induced high surface roughness, resulting in high COF. Low average roughness and retention of strength reduced COF in SD region. Dynamic recrystallization was an additional factor controlling material transfer in magnesium AZ31 alloy. Changes in oxide layer morphology were established based on the microstructural characterization of sample's surface and subsurface. In AA5083 alloy, crack formation at temperatures 500°C were found in the magnesium rich surface oxide. Magnesium rich surface oxide reduced COF, and low COF was found in the material having high magnesium. AZ31 alloy always showed lower COF compared to AA5083. This was confirmed by junction strength experiment where adhesion strength was found to be low in high magnesium content material. Therefore, this investigation on the plastic deformation and surface damage mechanism, and their relation with the tribological behaviour provided better understanding of the hot-forming process.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,001 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».