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The effect of precipitates on twinning in magnesium alloys
journal contribution
posted on 2019-04-01, 00:00 authored by J D Robson, Matthew BarnettMatthew BarnettUnderstanding how to strengthen against twin mediated deformation is critical for controlling the mechanical properties and formability of magnesium. One route to strengthening is through precipitation of shear resistant particles. This paper presents the current understanding of how precipitate particles and (Formula presented.) twins interact in magnesium, and how this influences strength. Precipitates increase the yield stress for twin dominated deformation but none of the current models reliably predict the strengthening effect. Precipitates have never been observed to completely suppress twinning, but usually lead to an increased number of narrower twins. Precipitates are not effective in increasing the stress for twin nucleation sufficiently to preferentially activate alternative deformation modes, but the effect on the stresses for both twin propagation and growth are significant. In the propagation stage, twin tips overcome precipitates by bowing of multiple twinning dislocations. For thick twins this can probably be assisted by pile up of twinning partials behind the tip. During growth, precipitates increase the stress to propagate new twinning steps, mainly due to increasing the unrelaxed back-stress. Since nucleation, propagation, and growth of twins all have to occur before macroscopic yield, a complete model to predict the strengthening effect must consider all of these stages.
History
Journal
Advanced engineering materialsVolume
21Issue
4Season
Special section: light materials – science and technologyArticle number
1800460Pagination
1 - 10Publisher
John Wiley & SonsLocation
Chichester, Eng.Publisher DOI
ISSN
1438-1656eISSN
1527-2648Language
engPublication classification
C1 Refereed article in a scholarly journalCopyright notice
2018, WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimUsage metrics
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