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Controlling and modelling of twin induced strain localization in rolling of magnesium AZ31

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2019
İsmail, Kübra
Formability of AZ31 Magnesium alloy has certain limits below 200 ℃ and depends strongly on temperature, due to the strain localization and shear banding associated with the twinning activity. In this thesis, magnesium sheets with basal, off-basal (90° tilted) and mixed (50% basal + 50% off-basal) textures are rolled between room temperature and 165 ℃ to understand and control the twinning-induced localizations. By increasing strain from 0.1 to 0.6 and raising the temperature, the fraction of flow localized regions increases and the strain intensity in these regions is controlled by the starting texture. The sheet with basal texture develops the most intense localizations at room temperature and fails by shear banding at only 0.16 strain. Off-basal sheet, on the other hand, has similar fraction of twins and localizations but capable of deforming twice the strain (0.36) without shear banding. Maximum uniform strains increase with temperature and reach to 0.60, 0.50, and 0.33 at 165 ℃ for off-basal, mixed, and basal textures, respectively. When the fraction of strain localized regions and the strain intensity in them are incorporated into a model, it was possible to predict the maximum rolling strain for a given starting texture and temperature.