Special Issue "Plasticity of Crystals and Interfaces"

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: closed (18 July 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Sinisa Dj. Mesarovic

School of Mechanical & Materials Engineering, Washington State University, PO Box 642920, Pullman, Washington 99164-2920, USA
Website | E-Mail
Interests: plasticity of crystals and interfaces; granular materials; coupled problems with moving boundaries; multiscale/multiphysics models

Special Issue Information

Dear Colleagues,

Eight decades ago, brilliant insights of Orowan, Polanyi and Taylor brought about understanding of the basic plasticity mechanisms in crystals and ushered a new era of exploration of basic mechanical properties of polycrystalline materials. Much has been learned and many phenomena are either understood qualitatively or incorporated into predictive models. Nevertheless, some important questions still elude our efforts to fully comprehend plasticity of polycrystals and crystalline composites. The list of keywords given below provides brief summary of the open issues. The list is illustrative and the contributions are not limited to these topics.

The interactions of crystal dislocations with interfaces and with the interface dislocation structure have been investigated at length in past few decades, but the sheer complexity of the problem has, thus far, prevented a systematic description.  Moreover, these interactions are the key component of the observed size effects in plasticity. The problem is compounded by the variety of mechanisms for interface mobility at low and high temperatures. In a single crystal, the kinematics of glide at low temperatures is well understood, but the dislocation climb and its interaction with vacancy diffusion still lacks the full mathematical description.

The Special Issue on “Plasticity of Crystals and Interfaces” is intended as a forum to present the current state-of-the-art and recent advances, as well as to suggest the future directions. Experimental, computational and theoretical contributions are invited. Of particular interest are the contributions that provide understanding of micro-scale mechanisms and/or enable their description within meso-scale models.

Prof. Dr. Sinisa Dj. Mesarovic
Guest Editor

Manuscript Submission Information

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Keywords

•    Interface plasticity
•    Dislocation climb and diffusion
•    Grain boundary sliding and migration
•    Size-effects in plasticity
•    Dislocation nucleation

Published Papers (7 papers)

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Research

Open AccessArticle Dislocation Creep: Climb and Glide in the Lattice Continuum
Crystals 2017, 7(8), 243; doi:10.3390/cryst7080243
Received: 9 June 2017 / Revised: 29 July 2017 / Accepted: 31 July 2017 / Published: 4 August 2017
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Abstract
A continuum theory for high temperature creep of polycrystalline solids is developed. It includes the relevant deformation mechanisms for diffusional and dislocation creep: elasticity with eigenstrains resulting from vacancy diffusion, dislocation climb and glide, and the lattice growth/loss at the boundaries enabled by
[...] Read more.
A continuum theory for high temperature creep of polycrystalline solids is developed. It includes the relevant deformation mechanisms for diffusional and dislocation creep: elasticity with eigenstrains resulting from vacancy diffusion, dislocation climb and glide, and the lattice growth/loss at the boundaries enabled by diffusion. All the deformation mechanisms are described with respect to the crystalline lattice, so that the continuum formulation with lattice motion as the basis is necessary. However, dislocation climb serves as the source sink of lattice sites, so that the resulting continuum has a sink/source of its fundamental component, which is reflected in the continuity equation. Climb as a sink/source also affects the diffusion part of the problem, but the most interesting discovery is the climb-glide interaction. The loss/creation of lattice planes through climb affects the geometric definition of crystallographic slip and necessitates the definition of two slip fields: the true slip and the effective slip. The former is the variable on which the dissipative power is expanded during dislocation glide and is thus, the one that must enter the glide constitutive equations. The latter describes the geometry of the slip affected by climb, and is necessary for kinematic analysis. Full article
(This article belongs to the Special Issue Plasticity of Crystals and Interfaces)
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Open AccessArticle On the Derivation of Boundary Conditions for Continuum Dislocation Dynamics
Crystals 2017, 7(8), 235; doi:10.3390/cryst7080235
Received: 10 July 2017 / Revised: 27 July 2017 / Accepted: 28 July 2017 / Published: 30 July 2017
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Abstract
Continuum dislocation dynamics (CDD) is a single crystal strain gradient plasticity theory based exclusively on the evolution of the dislocation state. Recently, we derived a constitutive theory for the average dislocation velocity in CDD in a phase field-type description for an infinite domain.
[...] Read more.
Continuum dislocation dynamics (CDD) is a single crystal strain gradient plasticity theory based exclusively on the evolution of the dislocation state. Recently, we derived a constitutive theory for the average dislocation velocity in CDD in a phase field-type description for an infinite domain. In the current work, so-called rational thermodynamics is employed to obtain thermodynamically consistent boundary conditions for the dislocation density variables of CDD. We find that rational thermodynamics reproduces the bulk constitutive equations as obtained from irreversible thermodynamics. The boundary conditions we find display strong parallels to the microscopic traction conditions derived by Gurtin and Needleman (M.E. Gurtin and A. Needleman, J. Mech. Phys. Solids 53 (2005) 1–31) for strain gradient theories based on the Kröner–Nye tensor. Full article
(This article belongs to the Special Issue Plasticity of Crystals and Interfaces)
Open AccessArticle Incompatibility Stresses and Lattice Rotations Due to Grain Boundary Sliding in Heterogeneous Anisotropic Elasticity
Crystals 2017, 7(7), 203; doi:10.3390/cryst7070203
Received: 29 April 2017 / Revised: 23 June 2017 / Accepted: 26 June 2017 / Published: 4 July 2017
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Abstract
Non-uniform grain boundary sliding can induce strain and rotation incompatibilities at perfectly planar interfaces. Explicit analytic expressions of stress and lattice rotation jumps are thus derived at a planar interface in the general framework of heterogeneous anisotropic thermo-elasticity with plasticity and grain boundary
[...] Read more.
Non-uniform grain boundary sliding can induce strain and rotation incompatibilities at perfectly planar interfaces. Explicit analytic expressions of stress and lattice rotation jumps are thus derived at a planar interface in the general framework of heterogeneous anisotropic thermo-elasticity with plasticity and grain boundary sliding. Both elastic fields are directly dependent on in-plane gradients of grain boundary sliding. It is also shown that grain boundary sliding is a mechanism that may relax incompatibility stresses of elastic, plastic and thermal origin although the latter are not resolved on the grain boundary plane. This relaxation may be a driving force for grain boundary sliding in addition to the traditionally considered local shears on the grain boundary plane. Moreover, the obtained analytic expressions are checked by different kinds of bicrystal shearing finite element simulations allowing grain boundary sliding and where a pinned line in the interface plane aims at representing the effect of a triple junction. A very good agreement is found between the analytic solutions and the finite element results. The performed simulations particularly emphasize the role of grain boundary sliding as a possible strong stress generator around the grain boundary close to the triple line because of the presence of pronounced gradients of sliding. Full article
(This article belongs to the Special Issue Plasticity of Crystals and Interfaces)
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Open AccessArticle Combining Single- and Poly-Crystalline Measurements for Identification of Crystal Plasticity Parameters: Application to Austenitic Stainless Steel
Crystals 2017, 7(6), 181; doi:10.3390/cryst7060181
Received: 24 April 2017 / Revised: 12 June 2017 / Accepted: 16 June 2017 / Published: 21 June 2017
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Abstract
Crystal plasticity finite element models have been extensively used to simulate various aspects of polycrystalline deformations. A common weakness of practically all models lies in a relatively large number of constitutive modeling parameters that, in principle, would require dedicated measurements on proper length
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Crystal plasticity finite element models have been extensively used to simulate various aspects of polycrystalline deformations. A common weakness of practically all models lies in a relatively large number of constitutive modeling parameters that, in principle, would require dedicated measurements on proper length scales in order to perform reliable model calibration. It is important to realize that the obtained data at different scales should be properly accounted for in the models. In this work, a two-scale calibration procedure is proposed to identify (conventional) crystal plasticity model parameters on a grain scale from tensile test experiments performed on both single crystals and polycrystals. The need for proper adjustment of the polycrystalline tensile data is emphasized and demonstrated by subtracting the length scale effect, originating due to grain boundary strengthening, following the Hall–Petch relation. A small but representative volume element model of the microstructure is identified for fast and reliable identification of modeling parameters. Finally, a simple hardening model upgrade is proposed to incorporate the grain size effects in conventional crystal plasticity. The calibration strategy is demonstrated on tensile test measurements on 316L austenitic stainless steel obtained from the literature. Full article
(This article belongs to the Special Issue Plasticity of Crystals and Interfaces)
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Open AccessArticle Distribution of Dislocations near the Interface in AlN Crystals Grown on Evaporated SiC Substrates
Crystals 2017, 7(6), 163; doi:10.3390/cryst7060163
Received: 30 April 2017 / Revised: 27 May 2017 / Accepted: 1 June 2017 / Published: 4 June 2017
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Abstract
To exploit unique properties of thin films of group III-nitride semiconductors, the production of native substrates is to be developed. The best choice would be AlN; however, presently available templates on sapphire or SiC substrates are defective. The quality of AlN could be
[...] Read more.
To exploit unique properties of thin films of group III-nitride semiconductors, the production of native substrates is to be developed. The best choice would be AlN; however, presently available templates on sapphire or SiC substrates are defective. The quality of AlN could be improved by eliminating the substrate during the layer growth. In this paper, we demonstrate freestanding AlN layers fabricated by an SiC substrate evaporation method. Such layers were used to investigate dislocation structures near the former AlN–SiC interface. Specimens were characterized by synchrotron radiation imaging, triple-axis diffractometry and transmission electron microscopy (TEM). We found that the evaporation process under non-optimal conditions affected the dislocation structure. When the growth had been optimized, AlN layers showed a uniform distribution of dislocations. The dislocations tended to constitute low-angle subgrain boundaries, which produced out-of-plane and in-plane tilt angles of about 2–3 arc-min. Similar broadening was observed in both symmetric and asymmetric rocking curves, which proved the presence of edge, screws as well as mixed dislocation content. TEM revealed arrays of edge threading dislocations, but their predominance over the other threading dislocations was not supported by present study. To explain the experimental observations, a theoretical model of the dislocation structure formation is proposed. Full article
(This article belongs to the Special Issue Plasticity of Crystals and Interfaces)
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Open AccessArticle Modeling and Characterization of Grain Boundaries and Slip Transmission in Dislocation Density-Based Crystal Plasticity
Crystals 2017, 7(6), 152; doi:10.3390/cryst7060152
Received: 4 May 2017 / Revised: 19 May 2017 / Accepted: 22 May 2017 / Published: 24 May 2017
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Abstract
In this study, a dislocation density-based model is introduced to analyze slip transmission across grain boundaries in polycrystalline materials. The method applies a combination of the misorientation of neighboring grains and resolved shear stress on relative slip planes. This model is implemented into
[...] Read more.
In this study, a dislocation density-based model is introduced to analyze slip transmission across grain boundaries in polycrystalline materials. The method applies a combination of the misorientation of neighboring grains and resolved shear stress on relative slip planes. This model is implemented into a continuum dislocation dynamics framework and extended to consider the physical interaction between mobile dislocations and grain boundaries. The model takes full account of the geometry of the grain boundary, the normal and direction of incoming and outgoing slip systems, and the extended stress field of the boundary and dislocation pileups at the boundary. The model predicts that slip transmission is easier across grain boundaries when the misorientation angle between the grains is small. The modeling results are verified with experimental nanoindentation results for polycrystalline copper samples. Full article
(This article belongs to the Special Issue Plasticity of Crystals and Interfaces)
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Open AccessFeature PaperArticle Validation of the Concurrent Atomistic-Continuum Method on Screw Dislocation/Stacking Fault Interactions
Crystals 2017, 7(5), 120; doi:10.3390/cryst7050120
Received: 7 March 2017 / Revised: 10 April 2017 / Accepted: 19 April 2017 / Published: 26 April 2017
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Abstract
Dislocation/stacking fault interactions play an important role in the plastic deformation of metallic nanocrystals and polycrystals. These interactions have been explored in atomistic models, which are limited in scale length by high computational cost. In contrast, multiscale material modeling approaches have the potential
[...] Read more.
Dislocation/stacking fault interactions play an important role in the plastic deformation of metallic nanocrystals and polycrystals. These interactions have been explored in atomistic models, which are limited in scale length by high computational cost. In contrast, multiscale material modeling approaches have the potential to simulate the same systems at a fraction of the computational cost. In this paper, we validate the concurrent atomistic-continuum (CAC) method on the interactions between a lattice screw dislocation and a stacking fault (SF) in three face-centered cubic metallic materials—Ni, Al, and Ag. Two types of SFs are considered: intrinsic SF (ISF) and extrinsic SF (ESF). For the three materials at different strain levels, two screw dislocation/ISF interaction modes (annihilation of the ISF and transmission of the dislocation across the ISF) and three screw dislocation/ESF interaction modes (transformation of the ESF into a three-layer twin, transformation of the ESF into an ISF, and transmission of the dislocation across the ESF) are identified. Our results show that CAC is capable of accurately predicting the dislocation/SF interaction modes with greatly reduced DOFs compared to fully-resolved atomistic simulations. Full article
(This article belongs to the Special Issue Plasticity of Crystals and Interfaces)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

 

 

 

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