Mechanism of Stress-Driven Grain Boundary Migration in Nanotwinned Materials

2018 ◽  
Vol 55 (1) ◽  
pp. 21-25 ◽  
Author(s):  
N.V. Skiba
Keyword(s):  
Theoretical Model ◽  
Grain Boundary ◽  
Twin Boundary ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
High Angle ◽  
Twin Boundaries ◽  
Critical Stresses ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Abstract Stress-driven grain boundary (GB) migration in ultrafine-grained materials with nanotwinned structure is theoretically described. In the framework of the theoretical model, the stress-driven high-angle GB migration is accompanied by migration of twin boundaries which adjoin this GB. Energetic characteristics and critical stresses of the GB migration accompanied by the twin boundary migration are calculated.

Simulation of Recrystallization Using Molecular Dynamics; Effects of the Interatomic Potential

2007 ◽  
Vol 558-559 ◽  
pp. 1081-1086 ◽  
Author(s):  
Rasmus B. Godiksen ◽  
Zachary T. Trautt ◽  
Moneesh Upmanyu ◽  
Søren Schmidt ◽  
Dorte Juul Jensen
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Interatomic Potential ◽  
Driving Forces ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
High Angle ◽  
Embedded Atom ◽  
Atomic Interactions

Recrystallization is governed by the migration of high angle grain boundaries traveling through a deformed material driven by the excess energy located primarily in dislocation structures. A method for investigating the interaction between a migrating grain boundary and dislocation boundaries using molecular dynamics (MD) was recently developed. During simulations migrating high angle grain boundaries interact with dislocation boundaries, and individual dislocations from the dislocation boundaries are absorbed into the grain boundaries. Results obtained previously, using a simple Lennard-Jones (LJ) potential, showed surprisingly irregular grain boundary migration compared to simulations of grain boundary migration applying other types of driving forces. Inhomogeneous boundary-dislocation interactions were also observed in which the grain boundaries locally acquired significant cusps during dislocation absorption events. The study presented here makes comparisons between simulations performed using a LJ- and an embedded atom method (EAM) aluminum potential. The results show similarities which indicate that it is the crystallographic features rather than the atomic interactions that determine the details of the migration process.

scholarly journals High-Angle Grain Boundary Migration in Aluminium Bicrystals

1995 ◽  
Vol 05 (C3) ◽  
pp. C3-89-C3-106 ◽  
Author(s):  
G. Gottstein ◽  
D. A. Molodov ◽  
U. Czubayko ◽  
L. S. Shvindlerman
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
High Angle

scholarly journals Investigating the dislocation reactions on Σ3{111} twin boundary during deformation twin nucleation process in an ultrafine-grained high-manganese steel

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chang-Yu Hung ◽  
Tomotsugu Shimokawa ◽  
Yu Bai ◽  
Nobuhiro Tsuji ◽  
Mitsuhiro Murayama
Keyword(s):  
Grain Boundary ◽  
Twin Boundary ◽  
Deformation Twin ◽  
Coarse Grained ◽  
Manganese Steel ◽  
High Manganese ◽  
Twin Boundaries ◽  
Dominant Type ◽  
Twin Nucleation ◽  
Ultrafine Grained

AbstractSome of ultrafine-grained (UFG) metals including UFG twinning induced plasticity (TWIP) steels have been found to overcome the paradox of strength and ductility in metals benefiting from their unique deformation modes. Here, this study provides insights into the atomistic process of deformation twin nucleation at Σ3{111} twin boundaries, the dominant type of grain boundary in this UFG high manganese TWIP steel. In response to the applied tensile stresses, grain boundary sliding takes place which changes the structure of coherent Σ3{111} twin boundary from atomistically smooth to partly defective. High resolution transmission electron microscopy demonstrates that the formation of disconnection on Σ3{111} twin boundaries is associated with the motion of Shockley partial dislocations on the boundaries. The twin boundary disconnections act as preferential nucleation sites for deformation twin that is a characteristic difference from the coarse-grained counterpart, and is likely correlated with the lethargy of grain interior dislocation activities, frequently seen in UFG metals. The deformation twin nucleation behavior will be discussed based on in-situ TEM deformation experiments and nanoscale strain distribution analyses results.

Observation of Stress-Driven Migration of Specific Planar Grain Boundaries in Al Bicrystals

2012 ◽  
Vol 706-709 ◽  
pp. 2886-2891 ◽  
Author(s):  
Dmitri A. Molodov ◽  
Tatiana Gorkaya ◽  
Günter Gottstein
Keyword(s):  
Shear Stress ◽  
Grain Boundary ◽  
Temperature Dependence ◽  
Boundary Migration ◽  
Activation Parameters ◽  
Tilt Boundary ◽  
Grain Boundary Migration ◽  
High Angle ◽  
Tilt Boundaries ◽  
Shear Coupling

Stress induced grain boundary migration was experimentally investigated in aluminum bicrystals. Migration of planar symmetrical <100> and <111> tilt boundaries under a shear stress was observed to be accompanied by a lateral translation of the adjacent grains. This coupling proved to be the typical migration mode for all investigated boundaries, no matter whether low-or high angle, low Σ CSL coincidence or non-coincidence boundary. The migration-shear coupling was also observed for asymmetrical tilt boundaries. Measurements of the temperature dependence of coupled boundary migration revealed that there is a specific misorientation dependence of the migration activation parameters. Contrary to expectations, a high angle Σ7 tilt boundary moved under an applied stress, but produced practically no shear during its migration.

A Mechanism for Particle Coalescence, Grain Growth and Twin Formation During Annealing of Gold Particles in an Amorphous Silica Matrix

1983 ◽  
Vol 21 ◽  
Author(s):  
J. McGinn ◽  
V.A. Greenhut ◽  
T. Tsakalakos
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Amorphous Silica ◽  
Direct Evidence ◽  
Boundary Migration ◽  
Silica Matrix ◽  
Grain Boundary Migration ◽  
High Angle ◽  
Gold Particles ◽  
Particle Coalescence

ABSTRACTDirect evidence was obtained for the coalescence of discrete gold particles (∼;lO0 nm) surrounded by a continuous amorphous silica matrix during annealing at 900°C. The particles were found to form high angle boundaries as coalescence occurred. Subsequent annealing revealed that grain growth occurred with relatively rapid elimination of high angle grain boundaries. The coalesced particles became approximately spherical in shape and seven particle morphologies could be distinguished. A majority of particles showed either no defect structure or conventional f.c.c. twins. In more limited cases, a small area of high angle grain boundary, usually of coincidence lattice type, was observed which accommodated intersecting twins. A single self-consistent mechanism can explain the elimination of high angle boundaries and all the various twin structures observed. The mechanism is based on Gleiter's [l] model for grain boundary migration with twin structures resulting from growth accidents on the migrating high angle boundary.

scholarly journals Модель растворения пор на границах зерен при отжиге ультрамелкозернистого алюминиевого сплава

2021 ◽  
Vol 47 (18) ◽  
pp. 40
Author(s):  
М.Ю. Гуткин ◽  
Т.С. Орлова ◽  
Н.В. Скиба
Keyword(s):  
Theoretical Model ◽  
Grain Boundary ◽  
Total Energy ◽  
Grain Boundaries ◽  
Ultrafine Grained ◽  
Model Pore ◽  
Ultrafine Grained Materials ◽  
Good Agreement ◽  
Zr Alloy

A theoretical model which describes the mechanism of pore dissolution at grain boundaries in ultrafine-grained materials during the ageing annealing is suggested. Within the framework of the model, pore dissolution occurs due to the emission of vacancies and the climb of grain-boundary dislocations along the grain boundary towards the pore. It is shown that in this case there is a significant decrease in the total energy of the system. The results of the model are in good agreement with the available experimental observations of pore dissolution during annealing of ultrafine-grained Al-Zr alloy.

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.

Measurement of solute segregation to grain boundaries in the AEM: A review

1988 ◽  
Vol 46 ◽  
pp. 606-607
Author(s):  
D. B. Williams ◽  
A. D. Romig
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Boundary Misorientation ◽  
Collector Plate ◽  
Segregation Process ◽  
Grain Boundary Misorientation ◽  
Structure Boundary ◽  
Equilibrium Segregation

The segregation of solute or imparity elements to grain boundaries can occur by three well-defined processes. The first is Gibbsian segregation in which an element of minimal matrix solubility confines itself to a monolayer at the grain boundary. Classical examples include Bi in Cu and S or P in Fe. The second process involves the depletion of excess matrix solute by volume diffusion to the boundary. In the boundary, the solute atoms diffuse rapidly to precipitates, causing them to grow by the ‘collector-plate mechanism.’ Such grain boundary diffusion is thought to initiate “Diffusion-Induced Grain Boundary Migration,” (DIGM). This process has been proposed as the origin of eutectoid transformations or discontinuous grain boundary reactions. The third segregation process is non-equilibrium segregation which result in a solute build-up around the boundary because of solute-vacancy interactions.All of these segregation phenomena usually occur on a sub-micron scale and are often affected by the nature of the grain boundary (misorientation, defect structure, boundary plane).

Domain coarsening by grain boundary migration in ordered Ni4Mo

1986 ◽  
Vol 44 ◽  
pp. 560-561
Author(s):  
K. Vasudevan ◽  
H. P. Kao ◽  
C. R. Brooks ◽  
E. E. Stansbury
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Short Range ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Rapid Cooling ◽  
Temperature Range ◽  
Fee Structure ◽  
Domain Coarsening ◽  
Boundary Reaction

The Ni4Mo alloy has a short-range ordered fee structure (α) above 868°C, but transforms below this temperature to an ordered bet structure (β) by rearrangement of atoms on the fee lattice. The disordered α, retained by rapid cooling, can be ordered by appropriate aging below 868°C. Initially, very fine β domains in six different but crystallographically related variants form and grow in size on further aging. However, in the temperature range 600-775°C, a coarsening reaction begins at the former α grain boundaries and the alloy also coarsens by this mechanism. The purpose of this paper is to report on TEM observations showing the characteristics of this grain boundary reaction.

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