scholarly journals Size-Dependent Solute Segregation at Symmetric Tilt Grain Boundaries in α-Fe: A Quasiparticle Approach Study

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4197
Author(s):  
Helena Zapolsky ◽  
Antoine Vaugeois ◽  
Renaud Patte ◽  
Gilles Demange
Keyword(s):  
Grain Boundaries ◽  
Hydrostatic Stress ◽  
Strain Tensor ◽  
Elastic Field ◽  
High Angle ◽  
Atomic Size ◽  
Symmetric Tilt ◽  
Wide Range ◽  
Solute Atoms ◽  
The Impact

In the present work, atomistic modeling based on the quasiparticle approach (QA) was performed to establish general trends in the segregation of solutes with different atomic size at symmetric ⟨100⟩ tilt grain boundaries (GBs) in α-Fe. Three types of solute atoms X1, X2 and X3 were considered, with atomic radii smaller (X1), similar (X2) and larger (X3) than iron atoms, respectively, corresponding to phosphorus (P), antimony (Sb) and tin (Sn). With this, we were able to evidence that segregation is dominated by atomic size and local hydrostatic stress. For low angle GBs, where the elastic field is produced by dislocation walls, X1 atoms segregate preferentially at the limit between compressed and dilated areas. Contrariwise, the positions of X2 atoms at GBs reflect the presence of tensile and compressive areal regions, corresponding to extremum values of the σXX and σYY components of the strain tensor. Regarding high angle GBs Σ5 (310) (θ = 36.95°) and Σ29 (730), it was found that all three types of solute atoms form Fe9X clusters within B structural units (SUs), albeit being deformed in the case of larger atoms (X2 and X3). In the specific case of Σ29 (730) where the GB structure can be described by a sequence of |BC.BC| SUs, it was also envisioned that the C SU can absorb up to four X1 atoms vs. one X2 or X3 atom only. Moreover, a depleted zone was observed in the vicinity of high angle GBs for X2 or X3 atoms. The significance of this research is the development of a QA methodology capable of ascertaining the atomic position of solute atoms for a wide range of GBs, as a mean to highlight the impact of the solute atoms’ size on their locations at and near GBs.

A Predictive Framework for Dislocation-Density Pile-Ups in Crystalline Systems With Coincident Site Lattice and Random Grain Boundaries

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
David M. Bond ◽  
Mohammed A. Zikry
Keyword(s):  
Dislocation Density ◽  
Grain Boundaries ◽  
Coincident Site Lattice ◽  
Local Stress ◽  
Face Centered Cubic ◽  
Slip Systems ◽  
Triple Junctions ◽  
High Angle ◽  
Site Lattice ◽  
Wide Range

Evolving dislocation-density pile-ups at grain-boundaries (GBs) spanning a wide range of coincident site lattice (CSL) and random GB misorientations in face-centered cubic (fcc) bicrystals and polycrystalline aggregates has been investigated. A dislocation-density GB interaction scheme coupled to a dislocation-density-based crystalline plasticity formulation was used in a nonlinear finite element (FE) framework to understand how different GB orientations and GB-dislocation-density interactions affect local and overall behavior. An effective Burger's vector of residual dislocations was obtained for fcc bicrystals and compared with molecular dynamics (MDs) predictions of static GB energy, as well as dislocation-density transmission at GB interfaces. Dislocation-density pile-ups and accumulations of residual dislocations at GBs and triple junctions (TJs) were analyzed for a polycrystalline copper aggregate with Σ1, Σ3, Σ7, Σ13, and Σ21 CSLs and random high-angle GBs to understand and predict the effects of GB misorientation on pile-up formation and evolution. The predictions indicate that dislocation-density pile-ups occur at GBs with significantly misoriented slip systems and large residual Burger's vectors, such as Σ7, Σ13, and Σ21 CSLs and random high-angle GBs, and this resulted in heterogeneous inelastic deformations across the GB and local stress accumulations. GBs with low misorientations of slip systems had high transmission, no dislocation-density pile-ups, and lower stresses than the high-angle GBs. This investigation provides a fundamental understanding of how different representative GB orientations affect GB behavior, slip transmission, and dislocation-density pile-ups at a relevant microstructural scale.

Grain Boundary Mechanics – Influence of Mechanical Stress Fields on Grain Boundaries

2004 ◽  
Vol 819 ◽  
Author(s):  
Myrjam Winning
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Mechanical Stress ◽  
Rotation Axis ◽  
Temperature Deformation ◽  
High Angle ◽  
Symmetric Tilt ◽  
In Situ Experiments ◽  
Grain Boundary Motion

AbstractThe reaction of grain boundaries to mechanical stresses is reviewed. Results of in-situ experiments on planar, symmetric tilt grain boundaries with different tilt axes (<112>, <111> and <100>) as well as twist grain boundaries with <100> rotation axis will be presented. It was found that the motion of planar grain boundaries can be induced by an imposed external stress irrespective of the angle of misorientation i.e. irrespective whether the grain boundary was a low or high angle grain boundary. The observed activation enthalpies of the stress induced grain boundary motion allow conclusions on the migration mechanism. The motion of planar low and high angle grain boundaries under the influence of a mechanical stress field can be attributed to the movement of the grain boundary dislocations which comprise the structure of the boundary. A sharp transition between low and high angle grain boundaries was observed for different tilt axes. The fact that boundaries can also be moved by mechanical forces sheds new light on microstructure evolution during elevated temperature deformation.

Electron Diffraction Applied to the Study of the Structure of (110) Tilt Boundaries in Fe-3% Si

1981 ◽  
Vol 39 ◽  
pp. 290-291
Author(s):  
E. L. Hall ◽  
C. L. Briant ◽  
J. L. Walter
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Grain Boundaries ◽  
High Purity ◽  
Periodic Structures ◽  
High Angle ◽  
Wide Range ◽  
Tilt Boundaries ◽  
Diffraction Effects ◽  
Matrix Reflection

It has become clear in recent years that both low-angle and high-angle grain boundaries can be described in terms of periodic structures. It has also been shown that much useful information concerning the structure of grain boundaries can be obtained by a combination of imaging and electron diffraction in the TEM. In the present study, these techniques are applied to the investigation of grain boundaries in high-purity Fe-3% Si. This material was chosen since very little work has been done to date on the structure of boundaries in bcc materials, and because it was possible to produce nearly pure (110) tilt boundaries with a wide range of angular misorientation in this material by a series of rolling and annealing treatments.The geometry of electron diffraction effects associated with grain boundaries has been extensively described in the literature. In the case of a boundary which is parallel to the electron beam and which has a periodicity present with a direction and a spacing P, a row of spots will occur in reciprocal space at each matrix reflection with a direction and a spacing 1/P.

Measurement of the Displacement Across a Coincidence Grain Boundary

1977 ◽  
Vol 35 ◽  
pp. 124-125
Author(s):  
J. W. Matthews ◽  
W. M. Stobbs
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stacking Fault ◽  
The Other ◽  
Measuring Technique ◽  
High Angle ◽  
Twin Boundaries ◽  
Rigid Displacement ◽  
Cubic Crystals ◽  
Lattice Displacement

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.

Observation of Atom Rows in Thorium Pyromellitate Using a Field Emission STEM

1977 ◽  
Vol 35 ◽  
pp. 80-81
Author(s):  
H. Todokoro ◽  
S. Nomura ◽  
T. Komoda
Keyword(s):  
Field Emission ◽  
Amorphous Carbon ◽  
Carbon Film ◽  
Dark Field Image ◽  
Dark Field ◽  
Amorphous Carbon Film ◽  
Atomic Size ◽  
Wide Range ◽  
A Chain

It is interesting to observe polymers at atomic size resolution. Some works have been reported for thorium pyromellitate by using a STEM (1), or a CTEM (2,3). The results showed that this polymer forms a chain in which thorium atoms are arranged. However, the distance between adjacent thorium atoms varies over a wide range (0.4-1.3nm) according to the different authors.The present authors have also observed thorium pyromellitate specimens by means of a field emission STEM, described in reference 4. The specimen was prepared by placing a drop of thorium pyromellitate in 10-3 CH3OH solution onto an amorphous carbon film about 2nm thick. The dark field image is shown in Fig. 1A. Thorium atoms are clearly observed as regular atom rows having a spacing of 0.85nm. This lattice gradually deteriorated by successive observations. The image changed to granular structures, as shown in Fig. 1B, which was taken after four scanning frames.

Observations of dislocation interactions with recrystallized grain boundaries

1988 ◽  
Vol 46 ◽  
pp. 628-629
Author(s):  
C. W. Price
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Dislocation Structure ◽  
Hot Deformation ◽  
Static Recrystallization ◽  
High Dislocation Density ◽  
High Angle ◽  
Dislocation Interactions

Little evidence exists on the interaction of individual dislocations with recrystallized grain boundaries, primarily because of the severely overlapping contrast of the high dislocation density usually present during recrystallization. Interesting evidence of such interaction, Fig. 1, was discovered during examination of some old work on the hot deformation of Al-4.64 Cu. The specimen was deformed in a programmable thermomechanical instrument at 527 C and a strain rate of 25 cm/cm/s to a strain of 0.7. Static recrystallization occurred during a post anneal of 23 s also at 527 C. The figure shows evidence of dissociation of a subboundary at an intersection with a recrystallized high-angle grain boundary. At least one set of dislocations appears to be out of contrast in Fig. 1, and a grainboundary precipitate also is visible. Unfortunately, only subgrain sizes were of interest at the time the micrograph was recorded, and no attempt was made to analyze the dislocation structure.

Determination of the lattice translation across {110} APBs in GaAs

1988 ◽  
Vol 46 ◽  
pp. 600-601
Author(s):  
D.R. Rasmussen ◽  
N.-H. Cho ◽  
C.B. Carter
Keyword(s):  
Grain Boundaries ◽  
Lower Energy ◽  
Antiphase Boundary ◽  
The Other ◽  
Boundary Structure ◽  
Interface Plane ◽  
Inversion Symmetry ◽  
High Angle ◽  
Equilibrium Distance

Domains in GaAs can exist which are related to one another by the inversion symmetry, i.e., the sites of gallium and arsenic in one domain are interchanged in the other domain. The boundary between these two different domains is known as an antiphase boundary [1], In the terminology used to describe grain boundaries, the grains on either side of this boundary can be regarded as being Σ=1-related. For the {110} interface plane, in particular, there are equal numbers of GaGa and As-As anti-site bonds across the interface. The equilibrium distance between two atoms of the same kind crossing the boundary is expected to be different from the length of normal GaAs bonds in the bulk. Therefore, the relative position of each grain on either side of an APB may be translated such that the boundary can have a lower energy situation. This translation does not affect the perfect Σ=1 coincidence site relationship. Such a lattice translation is expected for all high-angle grain boundaries as a way of relaxation of the boundary structure.

Precipitation on Low Angle Boundaries in Al-Zn-Mg

1980 ◽  
Vol 38 ◽  
pp. 374-375
Author(s):  
Diane M. Vanderwalker
Keyword(s):  
Grain Boundaries ◽  
High Strength ◽  
Boundary Structure ◽  
Aircraft Industry ◽  
Precipitate Free Zone ◽  
High Angle ◽  
Adjacent Region ◽  
Free Zone ◽  
Widespread Interest

There is a widespread interest in understanding the properties of Al-base alloys so that progress can be made toward extending their present applications in the aircraft industry. Al-Zn-Mg is precipitation hardened to gain its high strength; however, during aging the formation of heterogeneous precipitates on the grain boundaries creates a precipitate-free zone in the adjacent region. Since high angle grain boundaries are not easily characterized, it is difficult to establish a relationship between the precipitate and the boundary structure. Therefore, this study involves precipitation on low angle grain boundaries where the boundary and the precipitate can be fully analyzed.

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