Effects of changes in strain path on work hardening in cubic metals

Zandrahimi, Morteza; Platias, Spyridon; Frice, D.; Barrett, Douglas J.; Bate, P. S.; Roberts, W. T.

doi:10.1007/bf02666682

Cited by 48 publications

(22 citation statements)

References 20 publications

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“…As reported in several papers (Li and Bate, 1991;Wilson et al, 1990;Zandrahimi et al, 1989) and as observed here for the aluminum AA1050, strain-path changes can, beside the transient effects, produce also persistent changes. If not only the flow stress but also the hardening rate is transiently changed due to the change in the strain path, this will cause a permanent effect on the flow stress.…”

Section: Transient Hardening Due To the Strain-path Changesupporting

confidence: 81%

“…A review of the major works on these metals can be found in Barlat et al (2003). Metals with low stacking-fault energy, where the effect of the changes in the strain paths is less pronounced, were studied as well (Hutchinson et al, 1976;Lamba and Sidebottom, 1978a, b;Li et al, 2006;Sakharova et al, 2008;Schmitt et al, 1991;Zandrahimi et al, 1989). Recently, the influence of the strain-path changes on detwinning in hexagonal metals was studied in zirconium (Proust et al, 2010) and beryllium (Brown et al, 2012;Sisneros et al, 2010).…”

Section: Microstructure and Mechanical Behavior After Strain-path Chamentioning

confidence: 99%

“…After a sufficiently large pre-deformation, the work-softening can lead to instability, because the subsequent increase in work hardening may be insufficient to compensate the geometrical softening, and the result is very early strain localization and necking (Li and Bate, 1991). The influence of strain-path changes on ductility and formability has been the subject of many studies (Ghosh and Backofen, 1973;Hutchinson et al, 1976;Hutchinson and Davis, 1983;Laukonis, 1979;Laukonis and Ghosh, 1978;Li and Bate, 1991;Lloyd and Sang, 1979;Wagoner and Laukonis, 1983;Wilson et al, 1990;Zandrahimi et al, 1989). To our knowledge, only few simulations have been performed with the aim to study strain localization after a strain-path change (see e.g.…”

mentioning

confidence: 99%

“…However, while changes in work hardening are transient, the flow stress can be influenced permanently (Li and Bate, 1991;Sun and Wagoner, 2013;Wilson et al, 1990;Zandrahimi et al, 1989). This is referred to as permanent softening (Brown, 1977;Wilson et al, 1990).…”

mentioning

confidence: 99%

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Strain-path change induced transients in flow stress, work hardening and r-values in aluminum

Maník

Holmedal

Hopperstad

2015

International Journal of Plasticity

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Commercially pure aluminum with random texture was prestrained either by rolling or by uniaxial compression, and then tested in uniaxial tension to study the transients in flow stress, work hardening and r-value induced by the strain-path change. New experimental results are reported on the variation of the r-value and the permanently reduced work hardening subsequent to the strain-path change. A continuum plasticity model was developed that can reproduce the observed behavior. The model applies a second-order "delayed pointer" tensor to represent the microstructural anisotropy and was implemented into the finite element software LS-DYNA. The model was calibrated to the experimental data, and a simulation of early strain localization subsequent to an orthogonal strain-path change was compared to strain fields measured by a digital image correlation technique.2

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Section: Transient Hardening Due To the Strain-path Changesupporting

confidence: 81%

Section: Microstructure and Mechanical Behavior After Strain-path Chamentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Strain-path change induced transients in flow stress, work hardening and r-values in aluminum

Maník

Holmedal

Hopperstad

2015

International Journal of Plasticity

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“…It should be noted that local complex 3D stress states may develop from the applied uniaxial stresses due to the plastic incompatibility between the soft and hard lamellae. The stress state change will promote dislocation accumulation and interaction by activating more slip systems (11,30,31), similar to what occurs in gradient structures (11,31). This will effectively increase the incidental dislocation density.…”

Section: Strain Partitioningmentioning

confidence: 91%

Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility

Yang

Yuan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

1,275

451

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Grain refinement can make conventional metals several times stronger, but this comes at dramatic loss of ductility. Here we report a heterogeneous lamella structure in Ti produced by asymmetric rolling and partial recrystallization that can produce an unprecedented property combination: as strong as ultrafine-grained metal and at the same time as ductile as conventional coarse-grained metal. It also has higher strain hardening than coarse-grained Ti, which was hitherto believed impossible. The heterogeneous lamella structure is characterized with soft micrograined lamellae embedded in hard ultrafine-grained lamella matrix. The unusual high strength is obtained with the assistance of high back stress developed from heterogeneous yielding, whereas the high ductility is attributed to back-stress hardening and dislocation hardening. The process discovered here is amenable to large-scale industrial production at low cost, and might be applicable to other metal systems.back-stress hardening | heterogeneous lamella structure | ductility | strength | strain partitioning S trong or ductile? For centuries engineers have been forced to choose one of them, not both as they would like to. This is because a material is either strong or ductile but rarely both at the same time. High strength is always desirable, especially under the current challenge of energy crisis and global warming, where stronger materials can help by making transportation vehicles lighter to improve their energy efficiency. However, good ductility is also required to prevent catastrophic failure during service.Grain refinement has been extensively explored to strengthen metals. Ultrafine-grained (UFG) and nanostructured metals can be many times stronger than their conventional coarse-grained (CG) counterparts (1-5), but low ductility is a roadblock to their practical applications. The low ductility is primarily due to their low strain hardening (6-12), which is caused by their small grain sizes. To further exacerbate the problem, their high strengths require UFG metals to have even higher strain hardening than weaker CG metals to maintain the same ductility according to the Considère criterion. This makes it appear hopeless for UFG materials to have high ductility and it has been taken for granted that they are super strong but inevitably much less ductile than their CG counterparts. Microstructure of Heterogeneous Lamella StructureHere we report that a previously unidentified heterogeneous lamella (HL) structure possesses both the UFG strength and the CG ductility, which to our knowledge has never been realized before. The HL structure was produced by asymmetric rolling (13, 14) and subsequent partial recrystallization (see Materials and Methods for details). The asymmetric rolling elongated the initial equiaxed grains (Fig. 1A) into a lamella structure (Fig. 1B), which is heterogeneous with some areas having finer lamella spacing than others. This was due to the variation of slip systems and plastic strain in grains with different initial orientation ...

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Modeling of Transients as a Response to Changes in Strain–Path of Commercially Pure Aluminium

Mánic¹,

Holmedal²,

Hopperstad³

2012

ICAA13: 13th International Conference on Aluminum Alloys

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Effects of changes in strain path on work hardening in cubic metals

Cited by 48 publications

References 20 publications

Strain-path change induced transients in flow stress, work hardening and r-values in aluminum

Strain-path change induced transients in flow stress, work hardening and r-values in aluminum

Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility

Modeling of Transients as a Response to Changes in Strain–Path of Commercially Pure Aluminium

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