Influence of orientation on twin nucleation and growth at low strains in a magnesium alloy Barnett, MR, Ghaderi, A, Quinta Da Fonseca, J and Robson, JD 2014, Influence of orientation on twin nucleation and growth at low strains in a magnesium alloy, Acta Materialia, vol. 80, pp. 380-391, doi: 10.1016/j.actamat.2014.07.013. Attached Files Name Description MIMEType Size Downloads Title Influence of orientation on twin nucleation and growth at low strains in a magnesium alloy Author(s) Barnett, MR orcid.org/0000-0001-8287-9044 Ghaderi, A orcid.org/0000-0002-6774-9302 Quinta Da Fonseca, J Robson, JD Journal name Acta Materialia Volume number 80 Start page 380 End page 391 Publisher Elsevier Place of publication Amsterdam, The Netherlands Publication date 2014 ISSN 1359-6454 Keyword(s) Crystal plasticity EBSD Magnesium Twin nucleation and growth Science & Technology Technology Materials Science, Multidisciplinary Metallurgy & Metallurgical Engineering Materials Science SITU NEUTRON-DIFFRACTION FINITE-ELEMENT APPROACH MG ALLOY DEFORMATION PLASTICITY PROPAGATION BEHAVIOR COMPRESSION TEMPERATURE RELAXATION Summary The resolved shear stress is believed to play an important role in twin formation. The present study tests this idea for an extruded magnesium alloy by examining "tension" twinning in different grain orientations. Electron backscatter diffraction analysis is employed for alloy AZ31 tested in compression along the extrusion axis to strains between 0.008 and 0.015. For heavily twinned grains, it is seen that twinning occurs on 2.3 twin systems per grain on average. The active systems are also most commonly those with, or very near to, the highest Schmid factor. The most active system in multiply twinned grains accounts on average for ∼0.6 of the twinning events. In addition, it is found that the twin habit plane falls within 6° of the K1 plane. Orientations with the highest Schmid factors (0.45-0.5) for twinning display twin aspect ratios greater by ∼40% and twin number densities greater by ∼10 times than orientations with maximum Schmid factors for twinning of 0.15-0.2. Thus the Schmid factor for twinning is seen to affect nucleation more than thickening in the present material. Viscoplastic crystal plasticity simulations are employed to obtain approximations for the resolved shear stress. Both the twin aspect ratio and number density correlate quite well with this term. The effect of the former can be assumed to be linear and that of the latter follows a power law with exponent ∼13. Increased aspect ratios and number densities are seen at low Schmid factors and this may relate to stress fluctuations, caused most probably in the present material by the stress fields at the tips of blocked twins. Overall, it is evident that the dominance of twinning on high Schmid factor systems is preserved at the low strains examined in the present work, despite the stress fluctuations known to be present. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Language eng DOI 10.1016/j.actamat.2014.07.013 Field of Research 091207 Metals and Alloy Materials Socio Economic Objective 861199 Basic Metal Products (incl. Smelting HERDC Research category C1 Refereed article in a scholarly journal ERA Research output type C Journal article Copyright notice ©2014, Elsevier Persistent URL http://hdl.handle.net/10536/DRO/DU:30069823 Document type: Journal Article Collection: Institute for Frontier Materials Related Links Link Description Connect to published version Go to link with your DU access privileges     Unless expressly stated otherwise, the copyright for items in DRO is owned by the author, with all rights reserved. Versions Version Filter Type Wed, 18 Feb 2015, 13:41:48 EST Wed, 18 Feb 2015, 13:42:19 EST Thu, 19 Feb 2015, 04:01:56 EST Tue, 24 Mar 2015, 08:56:11 EST Wed, 22 Apr 2015, 06:09:52 EST Thu, 23 Apr 2015, 12:07:33 EST Thu, 23 Apr 2015, 12:08:16 EST Wed, 13 May 2015, 09:00:56 EST Tue, 13 Feb 2018, 11:20:36 EST Filtered Full Citation counts:   Cited 36 times in TR Web of Science Cited 39 times in Scopus Search Google Scholar Access Statistics: 319 Abstract Views, 2 File Downloads  -  Detailed Statistics Created: Wed, 18 Feb 2015, 13:42:19 EST

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