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Discontinuous yielding in wrought magnesium

journal contribution
posted on 2017-05-01, 00:00 authored by G Timár, Matthew BarnettMatthew Barnett, J Q da Fonseca
Recent reports of discontinuous yielding in the uniaxial compression of extruded magnesium suggest that twinning is accompanied by a significant stress decrease in the parent grain, leading to corresponding stress concentrations. We performed crystal plasticity finite element simulations using a simple twinning implementation that includes this “softening” effect for tensile twinning. With this method we were able to reproduce the experimentally observed yield point elongation and the Lüders-like propagation of strain and twinning over the sample. Twin variant selection was analysed in detail at various stages of deformation. Although lower rank variants were found to be activated, most of the twinning activity occurred on variants with the highest global Schmid factor. The stress fluctuations arising from the stress relaxation due to twinning did not appear to alter the dominance of the highest Schmid factor variant significantly. However, when twin softening is included, the twinning strain is dominated by a single variant. Despite giving rise to the highest stress fluctuations during yielding, simulations using the twin stress relaxation implementation actually showed less heterogeneity in stress after yielding. The results of our simple model suggest that “twin softening” could be key to the development of discontinuous yielding in extruded magnesium alloys.

History

Journal

Computational materials science

Volume

132

Pagination

81 - 91

Publisher

Elsevier

Location

Amsterdam, The Netherlands

ISSN

0927-0256

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2017, Elsevier B.V.