Variant selection during secondary twinning in Mg–3%Al

Martin, Étienne; Capolungo, Laurent; Jiang, Lan; Jonas, John J.

doi:10.1016/j.actamat.2010.03.027

Cited by 174 publications

(81 citation statements)

References 3 publications

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“…All double twin types have been identified in deformed Mg alloys via electron backscattering diffraction (EBSD) or transmission electron microscopy analyses Cizek & Barnett 2008;Ando et al 2010;Martin et al 2010). Type 1 is the most frequently observed, even in situations in which the type 1 secondary twin variant is unfavourably oriented with respect to the applied loading Barnett et al 2008;Martin et al 2010).…”

Section: (A) Classification Of Double Twin Variants: Types 1-4mentioning

confidence: 99%

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Double twinning mechanisms in magnesium alloys via dissociation of lattice dislocations

et al. 2012

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In this work, we propose dislocation mechanisms for the formation of {1011}−{1012} double twin structures in hexagonal close packed (HCP) crystals through the nucleation of secondary twins within primary twin domains. The model considers that secondary twins associated with the most commonly observed double twin variants (i.e. type 1 and type 2) nucleate and thicken by a sequence of three distinct dissociation reactions of mixed basal dislocations. Provided that the less frequently observed double twin variants (i.e. type 3 and type 4) also form by a dislocation-based mechanism, we show that their development must proceed by a separate set of dissociation reactions involving pyramidal c + a slip dislocations. Mechanistic, crystallographic and energetic considerations indicate that the type 1 variant should be the most prevalent. The mechanisms proposed here would also apply to the analysis of {1013}−{1012} compound twins and HCP metals other than Mg that exhibit double twinning, such as titanium.

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Section: (A) Classification Of Double Twin Variants: Types 1-4mentioning

confidence: 99%

“…As a consequence, the results have proved inconsistent with experimental observations. Recent studies have found that one double twin type occurs most frequently Martin et al 2010) and its prevalence is not driven entirely by the macroscopic applied stress (i.e. Schmid factors).…”

Section: *Author For Correspondence (Irene@lanlgov)mentioning

confidence: 99%

Double twinning mechanisms in magnesium alloys via dissociation of lattice dislocations

et al. 2012

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“…One possible reason for this is a variation of the local stress state, due both to a variation in the plastic strain supported by each grain, and to internal stresses resulting from nearby twins, or from slip processes within the untwinned parts of a grain [13]. Related arguments, based on self-strain accommodation have been proposed to account for the variant selection during double twinning in Mg-alloys [1,14,25]. Based on in-situ 3D-XRD observations Aydiner et al have reported that the stress state within a twin can be significantly different from that in the untwinned matrix [19].…”

Section: Dependence On the Local Stress Conditionsmentioning

confidence: 99%

“…The grain orientation dependence of twinning within individual grains has been discussed by several authors in terms of a Schmid factor (SF) [1,[9][10][11][12][13][14][15][16] analogous to that used in the analysis of dislocation glide. Although in many cases primary twinning has been found to…”

Section: Introductionmentioning

confidence: 99%

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Extension twin variant selection during uniaxial compression of a magnesium alloy

Pei

Godfrey

Jiang

et al. 2012

Materials Science and Engineering: A

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Samples of the magnesium alloy AZ31 have been deformed by compression to strains of 5% and 10% and microstructural observations made to investigate the activation of specific {10-12} extension twin variants. The twinning has been analyzed on a grain-by-grain basis for more than 260 grains to determine both the number of extension twin variants in each grain, and the volume fraction of each. At 5% strain approx. 30% of the grains contain twins corresponding to variants with the third or lower ranked Schmid factor, with the fraction increasing to 40% after 10% compression. A grain size effect is also observed in that smaller grains are less likely to contain lower ranked twin variants. For both 5% and 10% compression no clear relationship exists between the volume fraction of each twin variant in a given grain population and the Schmid factor for the twin variant. A positive linear relationship can be defined, however, between the maximum twinning fraction that a twin variant can reach and its Schmid factor. TITLE PAGE Abstract:Samples of the magnesium alloy AZ31 have been deformed by compression to strains of 5% and 10% and microstructural observations made to investigate the activation of specific {1012} extension twin variants. The twinning has been analyzed on a grain-by-grain basis for more than 260 grains to determine both the number of extension twin variants in each grain, and the volume fraction of each. At 5% strain approx. 30% of the grains contain twins corresponding to variants with the third or lower ranked Schmid factor, with the fraction increasing to 40% after 10% compression. A grain size effect is also observed in that smaller grains are less likely to contain lower ranked twin variants. For both 5% and 10% compression no clear relationship exists between the volume fraction of each twin variant in a given grain population and the Schmid factor for the twin variant. A positive linear relationship can be defined, however, between the maximum twinning fraction that a twin variant can reach and its Schmid factor.

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Dislocation Activity in AZ31B Magnesium Deformed at Moderately Elevated Temperatures via EBSD

Ruggles

Khosravani

Fullwood

et al. 2014

Magnesium Technology 2014

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Variant selection during secondary twinning in Mg–3%Al

Cited by 174 publications

References 3 publications

Double twinning mechanisms in magnesium alloys via dissociation of lattice dislocations

Double twinning mechanisms in magnesium alloys via dissociation of lattice dislocations

Extension twin variant selection during uniaxial compression of a magnesium alloy

Dislocation Activity in AZ31B Magnesium Deformed at Moderately Elevated Temperatures via EBSD

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