Twinning-induced shear banding and its control in rolling of magnesium

2018-05-16
Atik, Kubra
Efe, Mert
Rolling of magnesium sheets is challenging at temperatures below 200 degrees C due to the strain localization and shear banding associated with the twinning activity. In this study, magnesium sheets with basal, off-basal (90 degrees tilted), and mixed (50% basal + 50% off-basal) textures are rolled between room temperature and 165 degrees C to understand and control the twinning-induced localizations. While the fraction of strain-localized regions increases from 0.1 to 0.6 with strain and temperature, the intensity of them are controlled by the starting textures. The sheet with basal texture develops the most intense localizations at room temperature, and fails by shear banding at 0.16 strain. Off-basal sheet, on the other hand, has similar fraction of twins and localizations but deforms to the strain of 0.36 without shear banding. Maximum uniform strains increase with temperature and reach to 0.60, 0.50, and 0.33 at 165 degrees C for off-basal, mixed, and basal textures, respectively. When the fraction and intensity of localizations are incorporated to a model treating the continuum as a composite, it is possible to capture the shear banding and failure during rolling. The model correctly predicts the maximum strains for a given starting texture and temperature.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

Suggestions

Transient and steady state photoelectronic analysis in TlInSe2 crystals
QASRAWI, ATEF FAYEZ HASAN; Hasanlı, Nızamı (Elsevier BV, 2011-08-01)
The temperature and illumination effects on the transient and steady state photoconductivities of TlInSe2 crystals have been studied. Namely, two recombination centres located at 234 and at 94 meV and one trap center located at 173 meV were determined from the temperature-dependent steady state and transient photoconductivities, respectively. The illumination dependence of photoconductivity indicated the domination of sublinear and supralinear recombination mechanisms above and below 160 K, respectively. Th...
Ultrathin oxynitridation process through ion implantation in a poly Si1-xGex gate MOS capacitor
Jacob, AP; Myrberg, T; Friesel, M; Nur, O; Willander, M; Serincan, U; Turan, Raşit (Elsevier BV, 2003-02-01)
Effect of temperature and time of heat treatment on the distribution of ion-implanted nitrogen in poly Si0.65Ge0.35 gate MOS samples was studied. Secondary ion mass spectrometry (SIMS) was used for the qualitative analysis of the nitrogen distribution. Rapid thermal processing was carried out for a temperature range of 950-1070degreesC for the redistribution of ions. The nitrogen implantation doses were 5 x 10(14) cm(-2), 2 x 10(15) cm(-2) and 5 x 10(15) cm(-2), all with an implantation energy of 50 keV. Fo...
Initiation and early growth of short fatigue cracks at inclusions
Kaynak, Cevdet; Baker, TJ (Informa UK Limited, 1996-05-01)
In this study, the initiation and early growth behaviour of short fatigue cracks in En7A steel with a high content of elongated MnS inclusions was investigated by generating and evaluating data on the growth of short fatigue cracks under various stress levels and stress ratios for the six principal specimen orientations. Short cracks usually initiated at the debonded interfaces between the matrix and the inclusions. If there was no debonding, cracking sometimes occurred in the inclusions. In the early stage...
Electrical conductivity and Hall mobility in p-type TlGaSe2 crystals
Qasrawi, AF; Hasanlı, Nızamı (Elsevier BV, 2004-07-02)
Systematic dark electrical conductivity and Hall mobility measurements have been carried out in the temperature range of 200-350 K on p-type TlGaSe2 crystals. The analysis of the temperature-dependent electrical conductivity and carrier concentration reveals the extrinsic type of conduction with an acceptor impurity level located at 0.33 eV, and donor and acceptor concentrations of 9.0 x 10(15) and 1.3 x 10(16) cm(-3), respectively. A hole and electron effective masses of 0.520m(0) and 0.325m(0), respective...
Flow transitions and flow localization in large-strain deformation of magnesium alloy
Sagapuram, Dinakar; Efe, Mert; Trumble, Kevin P.; Chandrasekar, Srinivasan (Elsevier BV, 2016-04-06)
Understanding transitions from homogeneous to localized flow, and mechanisms underlying flow localization, is of paramount importance for deformation processing of magnesium. In this study, a shear based deformation method is utilized for imposing large strains (similar to 1), under controllable strain rates (10-10(5)/s) and temperatures (80-300 degrees C), in order to examine flow patterns in a magnesium alloy. Based on microstructure characterization, deformation twinning is suggested to contribute to the...
Citation Formats
K. Atik and M. Efe, “Twinning-induced shear banding and its control in rolling of magnesium,” MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, pp. 267–273, 2018, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/56477.