Magnesium Sheet; Challenges and Opportunities
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Notice bibliographique
Résumé
Where light-weight components are desired, e.g. in automotive and aerospace applications, magnesium can provide an important advantage over other structural materials such as aluminum and steel. The density of magnesium is two thirds that of aluminum and a quarter that of galvanized steel. The combination of low density and reasonable strength of magnesium leads to a specific strength, which is much higher than that of steel or aluminum. Stiffness is often as important as strength and, with respect to bending stiffness, magnesium offers major advantages over both steel and aluminum. Using more magnesium would significantly decrease the weight of automobiles, which is one of the important goals in automobile design. However, usage of magnesium lags far behind that of aluminum. To date, most magnesium applications in the automobile industry are in the form of die cast parts. Wrought magnesium, particularly in the form of sheet, represents a tremendous growth opportunity in the application of magnesium, e.g. inner door panel, engine bonnet, seat components, roof, and fenders. The use of magnesium sheet is, however, severely limited because of: (a) the high cost of magnesium sheet, (b) the poor room temperature ductility of magnesium, and (c) the relatively high propensity to corrosion. Sheet materials are required to display sufficient formability when subjected to bending stresses during fabrication into parts. The poor plastic flow characteristics of magnesium at room temperature have considerably hampered its sheet applications. Essentially, because magnesium has a hexagonal close packed (hcp) structure, active slip systems at low temperatures are mainly limited to those involving basal planes. This is because the critical resolved shear stress (CRSS) for basal plane slip in magnesium single crystal is 100 times lower than that for non-basal plane slip (prismatic or pyramidal planes) near room temperature. Thus, the distribution of basal planes (0001) in magnesium plays an important role in determining formability at low temperatures. As the temperature increases, the CRSS of the non-basal slip systems decreases and, therefore, there is a significant increase in formability. Consequently, sheet forming at elevated temperatures is one possibility that is being contemplated, and there is considerable ongoing research in this general area, including those concerned with the viability of superplastic forming. In this chapter, the challenges to the production of magnesium sheet and the route toward overcoming them are explained. Then, deformation characteristics of magnesium and associated mechanisms are discussed.
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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 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,004 | 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 découle