On the evolution of crystallographic dislocation density in non-homogeneously deforming crystals

Arsenlis, A.; Parks, David M.; Becker, Richard; Bulatov, Vasily V.

doi:10.1016/j.jmps.2003.12.007

Cited by 240 publications

(186 citation statements)

References 46 publications

(58 reference statements)

Supporting

Mentioning

182

Contrasting

Unclassified

Order By: Relevance

“…J tms is the dislocation flux of direct transmission from bulk 1 to 2, J abs is the dislocation flux of direct transmission from bulk 1 to TB, and J des is the dislocation flux of direct transmission from TB to bulk 2. The ADT equation should generally serve as the boundary condition for crystal plasticity models that are predicated on bulk dislocation density ( bulk ) (35). However, for nanocrystalline metals, the role played by bulk crystal plasticity would be greatly diminished because dislocations seldom stay inside the bulk but are either absorbed into or piled up near the GB.…”

Section: Resultsmentioning

confidence: 99%

Interfacial plasticity governs strain rate sensitivity and ductility in nanostructured metals

Zhu

Li²,

Samanta³

et al. 2007

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

534

263

View full text Add to dashboard Cite

Nano-twinned copper exhibits an unusual combination of ultrahigh strength and high ductility, along with increased strain-rate sensitivity. We develop a mechanistic framework for predicting the rate sensitivity and elucidating the origin of ductility in terms of the interactions of dislocations with interfaces. Using atomistic reaction pathway calculations, we show that slip transfer reactions mediated by twin boundary are the rate-controlling mechanisms of plastic flow. We attribute the relatively high ductility of nanotwinned copper to the hardening of twin boundaries as they gradually lose coherency during plastic deformation. These findings provide insights into the possible means of optimizing strength and ductility through interfacial engineering.activation volume ͉ interfacial hardening ͉ nanoscale twins ͉ slip transfer reaction N anocrystalline metals with grain size finer than 100 nm routinely exhibit up to five times higher strength than their coarse-grained counterparts but suffer from greatly diminished ductility (1-3). showed that introduction of coherent nano-twins, typically tens of nanometers in thickness, in ultrafine-grained copper (with grain size of several hundred nanometers) leads to an unusual combination of ultrahigh strength (Ϸ1 GPa) and high ductility (14% elongation to failure). The plastic deformation characteristics of nanocrystalline metals have previously been rationalized on the basis of a number of mechanisms (7), including grain boundary (GB) sliding (8, 9), grain rotation (10), and diffusional creep (11). An effective experimental technique to probe the active deformation mechanism is to measure the sensitivity of flow stress to the rate of loading, ʈ because both the sensitivity index m and the associated activation volume v* can vary by orders of magnitude for different rate-limiting processes. For face-centered cubic metals such as copper, grain refinement into the nanocrystalline regime leads to an increase in m by up to an order of magnitude relative to microcrystalline metals with grain size in the micrometer range, and a concomitant decrease in the activation volume v* by two orders of magnitude (14,15). Nano-twinned copper shows the same characteristics of increased rate sensitivity and reduced activation volume as nanocrystalline copper without twins (4, 5, 12, 13) even when the average grain size is several hundred nanometers. However, it achieves very high strength without severely compromising ductility (4, 5).The commonly used strengthening model for nanocrystalline metals is the Hall-Petch relation (7, 16), which is a scaling function relating strength to grain size. The Hall-Petch relation is derived based on strengthening mechanisms (17) at internal interfaces, which proliferate in nanocrystals. However, it says nothing about ductility. To model ductility, it is necessary to revisit detailed physical processes at materials interfaces, in particular those involving dislocations, which are the carriers of plastic strain. Dislocation processes at internal interfac...

show abstract

Section: Resultsmentioning

confidence: 99%

Interfacial plasticity governs strain rate sensitivity and ductility in nanostructured metals

Zhu

Li²,

Samanta³

et al. 2007

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

534

263

View full text Add to dashboard Cite

show abstract

“…Similar problems have been encountered when implementing other theories dealing with dislocation plasticity. For instance, the streamline upwinding was used by Arsenlis et al [28] when implementing their edge-screw model, whereas the least-square Galerkin was utilized by Roy and Acharya [29] who dealt with equations quite similar to ours, however, resolving individual dislocations. The weighted essentially non-oscillatory method was used in the phase field modelling of individual dislocations by Xiang et al [30].…”

Section: Introductionmentioning

confidence: 99%

Continuum theory of evolving dislocation fields

Sedláček

Schwarz

Kratochvı́l

et al. 2007

Philosophical Magazine

View full text Add to dashboard Cite

International audienceContinuum theory of moving dislocations is used to set up a non-local constitutive law for crystal plasticity in the form of partial differential equations for evolving dislocation fields. The concept of single-valued dislocation fields that enables to keep track of the curvature of the continuously distributed gliding dislocations with line tension is utilized. The theory is formulated in the Eulerian as well as in so-called dislocation-Lagrangian forms. The general theory is then specialized to a form appropriate to formulate and solve plane-strain problems of continuum mechanics. The key equation of the specialized theory is identified as a transport equation of diffusion-convection type. The numerical instabilities resulting from the dominating convection are eliminated by resorting to the dislocation-Lagrangian approach. Several examples illustrate the application of the theory

show abstract

“…During deformation, a dislocation density of GNDs accumulates and makes the grain boundary strengthening, but the grains located at the free surface of micro specimen have less hardening effect than that of inner grains [32]. Therefore, the portion of flow stress attributed by dislocation density of GNDs in surface layer can be ignored, and the flow stress of surface layer can be expressed as:…”

Section: Constitutive Modellingmentioning

confidence: 99%

Influences of temperature and grain size on the material deformability in microforming process

Jiang

Zhao

et al. 2016

Int J Mater Form

View full text Add to dashboard Cite

This paper investigated the influences of temperature and grain size on the deformability of pure copper in micro compression process. Based on the dislocation theory, a constitutive model was proposed taking into account the influences of forming temperature, Hall-Petch relationship and surface layer model. Vacuum heat treatment was employed to obtain various grain sizes of cylindrical workpieces, and then laser heating method was applied to heat workpieces during microforming process. Finite element (FE) simulation was also performed, with simulated values agreed well with the experimental results in terms of metal flow stress. Both the FE simulated and experimental results indicate that forming temperature and grain size have a significant influence on the accuracy of the produced product shape and metal flow behaviour in microforming due to the inhomogeneity within the deformed material. The mechanical behaviour of the material is found to be more sensitive to forming temperature when the workpieces are constituted of fine grains. experimental results indicate that forming temperature and grain size have a significant influence on the accuracy of the produced product shape and metal flow behaviour in microforming due to the inhomogeneity within the deformed material. The mechanical behaviour of the material is found to be more sensitive to forming temperature when the workpieces are constituted of fine grains.

show abstract

On the evolution of crystallographic dislocation density in non-homogeneously deforming crystals

Cited by 240 publications

References 46 publications

Interfacial plasticity governs strain rate sensitivity and ductility in nanostructured metals

Interfacial plasticity governs strain rate sensitivity and ductility in nanostructured metals

Continuum theory of evolving dislocation fields

Influences of temperature and grain size on the material deformability in microforming process

Contact Info

Product

Resources

About