Grain Boundary Dynamics in High Magnetic Fields. Fundamentals and Implications for Materials Processing

2004 ◽  
Vol 467-470 ◽  
pp. 697-706 ◽  
Author(s):  
Dmitri A. Molodov
Keyword(s):  
Magnetic Fields ◽  
Grain Boundary ◽  
Boundary Migration ◽  
Materials Processing ◽  
High Magnetic Fields ◽  
Boundary Motion ◽  
Grain Boundary Mobility ◽  
Curvature Driven ◽  
Grain Boundary Motion ◽  
Boundary Dynamics

The latest research on dynamics of grain boundaries in non-magnetic materials in high magnetic fields is reviewed. A control of grain boundary migration means control of microstructure evolution, which is a key for the design of materials with desire properties. Grain boundary motion can be affected by a magnetic field, if the anisotropy of the magnetic susceptibility generates a gradient of the magnetic free energy. In contrast to curvature driven boundary motion, a magnetic driving force also acts on planar boundaries so that the motion of crystallographically well-defined boundaries can be investigated, and the true grain boundary mobility can be determined. The results of migration measurements obtained on bismuth and zinc bicrystals are addressed. Selective growth of new grains in locally deformed zinc single crystals driven by a magnetic force is reported as well. Implications for materials processing, in particular the effect of magnetic fields on texture development in hcp metals are finally discussed.

Grain Boundary Migration and Compensation Effect

2007 ◽  
Vol 550 ◽  
pp. 387-392
Author(s):  
Pavel Lejček
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Compensation Effect ◽  
Activation Enthalpy ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Boundary Motion ◽  
Exponential Factor ◽  
Grain Boundary Motion

Anisotropy of grain boundary motion in a Fe–6at.%Si alloy is represented by a spectrum of values of the activation enthalpy of migration and the pre-exponential factor, depending on the orientation of individual grain boundaries. The general plot of these values exhibits a pronounced linear interdependence called the compensation effect. It is shown that changes of these values, caused by changes of intensive variables, are thermodynamically consistent.

Transition State Model for Grain Boundary Motion During Ion Bombardment

1988 ◽  
Vol 100 ◽  
Author(s):  
Harry A. Atwater ◽  
Carl V. Thompsonm ◽  
Henry I. Smith
Keyword(s):  
Grain Boundary ◽  
Transition State ◽  
Boundary Migration ◽  
Ion Bombardment ◽  
State Model ◽  
Boundary Motion ◽  
Frenkel Defect ◽  
Thermally Induced ◽  
Two Phases ◽  
Grain Boundary Motion

ABSTRACTIon bombardment of polycrystalline Ge, Si, and Au films leads to rates of grain boundary motion that greatly exceed rates of thermally-induced motion at the same temperature and which exhibit a weak temperature dependence. The enhanced migration rate is proportional to the rate of energy deposition in nuclear collisions at or very near the grain boundary. Experimental work is reviewed, and a transition state model is presented which accounts for the observed kinetics of grain boundary migration during bombardment. This model suggests that the rate limiting step in grain boundary motion may be thermally-induced migration of a bombardment-generated defect across the boundary. Also, the ratio of atomic jumps at grain boundaries to the local collision-induced Frenkel defect generation rate is shown to be characteristic of each material, but independent of ion mass and ion flux. The model is extended to the motion of an interface between two phases, and applications to crystallization during ion bombardment are discussed.

Study of Deformation Behavior of Ultrafine-grained Materials Through in Situ Nanoindentation in a Transmission Electron Microscope

2005 ◽  
Vol 20 (7) ◽  
pp. 1735-1740 ◽  
Author(s):  
M. Jin ◽  
A.M. Minor ◽  
D. Ge ◽  
J.W. Morris
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Transmission Electron Microscope ◽  
Deformation Behavior ◽  
Boundary Migration ◽  
Boundary Motion ◽  
Transmission Electron ◽  
Ultrafine Grained ◽  
Grain Boundary Motion

The mechanical properties of ultrafine-grained and nanograined materials have received a great deal of recent attention because of their unusual and promising values. However, some of the most important mechanisms of deformation remain unclear. In this work, the deformation behavior of ultrafine-grained Al films and ultrafine-grained Fe is studied through in situ nanoindentation in a transmission electron microscope. Deformation-induced coarsening by grain boundary migration was observed in the ultrafine-grained Al films during deformation at room temperature, whereas no grain boundary motion was found in ultrafine-grained Fe. The lack of grain boundary motion in Fe was attributed to the pinning effect of nano-sized particles at the Fe grain boundaries.

Magnetically Controlled Grain Boundary Motion and Grain Growth in Zinc

2013 ◽  
Vol 753 ◽  
pp. 107-112 ◽  
Author(s):  
Christoph Günster ◽  
Dmitri A. Molodov ◽  
Günter Gottstein
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Driving Force ◽  
Boundary Migration ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Cold Rolled ◽  
Grain Growth Kinetics ◽  
Grain Boundary Motion

The motion of grain boundaries in zinc bicrystals (99.995%) driven by the “magnetic” driving force was investigated. Planar symmetrical and asymmetrical tilt grain boundaries with rotation angles in the range between 60° and 90° were examined. At a given temperature the boundary migration rate was found to increase linearly with an applied driving force. The absolute grain boundary mobility was determined. The boundary mobility and its temperature dependence were found to depend on the misorientation angle and the inclination of the boundary plane. An application of a magnetic field during the annealing of cold rolled (90%) Zn-1.1%Al sheet specimens resulted in an asymmetry of the two major texture components. This is interpreted in terms of magnetically affected grain growth kinetics.

Grain Growth Kinetics in Microcrystalline Materials

1994 ◽  
Vol 343 ◽  
Author(s):  
V. G. Sursaeva
Keyword(s):  
Activation Energy ◽  
Grain Boundary ◽  
Grain Growth ◽  
Dark Field ◽  
Boundary Mobility ◽  
Boundary Motion ◽  
Grain Boundary Mobility ◽  
Grain Growth Kinetics ◽  
Microcrystalline Materials ◽  
Grain Boundary Motion

ABSTRACTCertain experimental results are presented concerning grain growth in microcrystalline Ag films. Dark field TEM technique was used for the measurement of grain size, trijunction velocity and grain boundary mobility. We found that the activation energy for trijunction motion is 25.0 kJ/g.atom, and the activation energy for the grain boundary motion is 50.0 kJ/g.atom.

scholarly journals Regularities of Structural Rearrangements in Single- and Bicrystals Near the Contact Zone

2020 ◽  
pp. 301-322
Author(s):  
Konstantin P. Zolnikov ◽  
Dmitrij S. Kryzhevich ◽  
Aleksandr V. Korchuganov
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Contact Zone ◽  
Boundary Migration ◽  
Shear Loading ◽  
Structural Defects ◽  
Grain Boundary Migration ◽  
Boundary Motion ◽  
Symmetric Tilt ◽  
Grain Boundary Motion

AbstractThe chapter is devoted to the analysis of the features of local structural rearrangementsin nanostructured materialsunder shear loadingand nanoindentation. The study was carried out using molecular dynamics-based computer simulation. In particular, we investigated the features of symmetric tilt grain boundary migration in bcc and fcc metals under shear loading. The main emphasis was on identifying atomic mechanisms responsible for the migration of symmetric tilt grain boundaries. We revealed that grain boundaries of this type can move with abnormally high velocities up to several hundred meters per second. The grain boundary velocity depends on the shear rate and grain boundary structure. It is important to note that the migration of grain boundary does not lead to the formation of structural defects. We showed that grain boundary moves in a pronounced jump-like manner as a result of a certain sequence of self-consistent displacements of grain boundary atomic planes and adjacent planes. The number of atomic planes involved in the migration process depends on the structure of the grain boundary. In the case of bcc vanadium, five planes participate in the migration of the Σ5(210)[001] grain boundary, and three planes determine the Σ5(310)[001] grain boundary motion. The Σ5(310)[001] grain boundary in fcc nickel moves as a result of rearrangements of six atomic planes. The stacking order of atomic planes participating in the grain boundary migration can change. A jump-like manner of grain boundary motion may be divided into two stages. The first stage is a long time interval of stress increase during shear loading. The grain boundary is motionless during this period and accumulates elastic strain energy. This is followed by the stage of jump-like grain boundary motion, which results in rapid stress drop. The related study was focused on understanding the atomic rearrangements responsible for the nucleation of plasticity near different crystallographic surfaces of fcc and bcc metals under nanoindentation. We showed that a wedge-shaped region, which consists of atoms with a changed symmetry of the nearest environment, is formed under the indentation of the (001) surface of the copper crystallite. Stacking faults arise in the (111) atomic planes of the contact zone under the indentation of the (011) surface. Their escape on the side free surface leads to a step formation. Indentation of the (111) surface is accompanied by nucleation of partial dislocations in the contact zone subsequent formation of nanotwins. The results of the nanoindentation of bcc iron bicrystal show that the grain boundary prevents the propagation of structural defects nucleated in the contact zone into the neighboring grain.

X-Ray Method for Continuous Tracking of Grain Boundary Motion: Investigation of Grain Boundary Migration in Al-Bicrystals

1994 ◽  
Vol 157-162 ◽  
pp. 125-130
Author(s):  
U. Czubayko ◽  
Dmitri A. Molodov ◽  
B.-C. Petersen ◽  
Günter Gottstein ◽  
Lasar S. Shvindlerman
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Boundary Motion ◽  
Ray Method ◽  
X Ray ◽  
Grain Boundary Motion
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