In Situ Measurements of Magnetically Driven Grain Boundary Migration in Zn Bicrystals

2012 ◽  
Vol 715-716 ◽  
pp. 467-472
Author(s):  
Christoph Günster ◽  
Dmitri A. Molodov ◽  
Günter Gottstein
Keyword(s):  
Grain Boundary ◽  
Activation Enthalpy ◽  
Boundary Migration ◽  
Activation Parameters ◽  
Grain Boundary Migration ◽  
Boundary Mobility ◽  
Exponential Factor ◽  
Grain Boundary Mobility ◽  
Enthalpy Changes

The results of investigations of magnetically driven grain boundary migration in high purity (99.995%) zinc bicrystals are presented. In-situ measurements were conducted by means of a specially designed and fabricated polarization microscopy probe. The migration of planar tilt grain boundaries with various misorientation angles in the range between 60° and 90° was studied. The absolute grain boundary mobility and its temperature dependence was measured in the regime between 330°C and 415°C and the corresponding migration activation parameters were determined. The results revealed that there is a pronounced misorientation dependence of grain boundary mobility in the investigated angular range. The migration activation enthalpy was found to vary between 1.18 eV and 2.15 eV. The obtained activation parameters comply with the compensation law, i.e. the migration activation enthalpy changes linearly with the logarithm of the pre-exponential factor.

Magnetically Controlled Grain Boundary Migration and Microstructure Evolution in Zn

2013 ◽  
Vol 333 ◽  
pp. 101-106
Author(s):  
Dmitri A. Molodov ◽  
Christoph Günster ◽  
Günter Gottstein
Keyword(s):  
Magnetic Field ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Microstructure Evolution ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Cold Rolled

The migration of planar grain boundaries induced by a magnetic field was measured in specially grown zinc bicrystals (99.995%). Particularly, symmetrical and asymmetrical <> tilt grain boundaries with rotation angles in the range between 60° and 90° were investigated. Boundary migration was measured in-situ in the temperature range between 330°C and 415°C and the absolute values of grain boundary mobility were obtained. The results revealed that grain boundary mobility essentially depends 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 substantially affected the texture and microstructure evolution. This effect is attributed to the additional magnetic driving force for grain growth arising due to the magnetic anisotropy of zinc.

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.

The recrystallization process in some polycrystalline metals

1962 ◽  
Vol 267 (1328) ◽  
pp. 11-30 ◽  
Keyword(s):  
Activation Energy ◽  
Electron Microscope ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Recrystallization Process ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Polycrystalline Metals

Electron microscope observations on some polycrystalline metals suggest that after small to moderate deformation, recrystallization occurs by the migration of the original grain boundaries. A theory based on this mechanism can account for the known form of the recrystallization kinetics without necessarily introducing any anisotropy of grain boundary mobility. For this mechanism the so-called recrystallization activation energy is identical to the activation energy for grain boundary migration.

Investigation of Grain Boundary Migration in Situ by Synchrotron X-Ray Topography

1988 ◽  
Vol 143 ◽  
Author(s):  
C. L. Bauer ◽  
J. Gastaldi ◽  
C. Jourdan ◽  
G. Grange
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Boundary Structure ◽  
Grain Boundary Migration ◽  
X Ray ◽  
Grain Boundary Mobility ◽  
Advantages And Disadvantages ◽  
Grain Boundary Character ◽  
Crystallographic Facets

AbstractGrain boundary migration has been investigated in prestrained monocrystalline specimens of aluminum in situ, continuously and at temperatures ranging from 415 to 610°C by synchrotron (polychromatic) x-ray topography (SXRT). In general, new (recrystallized) grains nucleate at prepositioned surface indentations and expand into the prestrained matrix, revealing complex evolution of crystallographic facets and occasional generation of (screw) dislocations in the wake of the moving boundaries. Analysis of corresponding migration rates for several faceted grain boundaries yields activation energies ranging from 56 to 125 kCal/mole, depending on grain boundary character. it is concluded that grain boundary mobility is a sensitive function of grain boundary inclination, resulting in ultimate survival of low-mobility (faceted) inclinations as a natural consequence of growth selection. Advantages and disadvantages associated with measurement of grain boundary migration by SXRT are enumerated and corresponding results are interpreted in terms of fundamental relationships between grain boundary structure and corresponding migration kinetics.

Stress Induced Grain Boundary Motion in Al Bicrystals

2012 ◽  
Vol 715-716 ◽  
pp. 227-234 ◽  
Author(s):  
Dmitri A. Molodov ◽  
Tatiana Gorkaya ◽  
Günter Gottstein
Keyword(s):  
Grain Boundary ◽  
Activation Enthalpy ◽  
Boundary Migration ◽  
Activation Parameters ◽  
Boundary Region ◽  
Tilt Boundary ◽  
Grain Boundary Migration ◽  
Solute Content ◽  
Mobility Factor ◽  
Grain Boundary Motion

Recent results of experimental research into stress induced grain boundary migration in aluminum bicrystals are briefly reviewed. Boundary migration under a shear stress was observed to be coupled to a lateral translation of the grains for any <100> tilt boundary in the entire misorientation range (0-90°). Measurements of the temperature dependence of coupled boundary migration revealed that there is a specific misorientation dependence of migration activation parameters. Grain boundaries can act during their motion under the applied stress as sources of lattice dislocations that leads to the generation and growth of new grains in the boundary region. The rate of stress induced boundary migration decreases with increasing solute content in aluminum. Both the migration activation enthalpy and the pre-exponential mobility factor were found to increase with rising impurity concentration.

Grain Boundary Migration and Grain Growth Texture Evolution in Zn in a High Magnetic Field

2011 ◽  
Vol 702-703 ◽  
pp. 635-638
Author(s):  
Christoph Günster ◽  
Dmitri A. Molodov ◽  
Günter Gottstein
Keyword(s):  
Magnetic Field ◽  
Grain Boundary ◽  
Grain Growth ◽  
Texture Evolution ◽  
Boundary Migration ◽  
Activation Parameters ◽  
Boundary Plane ◽  
Grain Boundary Migration ◽  
Cold Rolled

The magnetically driven motion of planar symmetrical and asymmetrical <> tilt grain boundaries in high purity (99,995%) zinc bicrystals was measured in-situ by means of a po­la­rization microscopy probe in the temperature range between 330°C and 415°C and the corres­pon­ding migration activation parameters were obtained. The results revealed that grain boundary mobi­lity essentially depends on the misorientation angle and the inclination of the boundary plane. The magnetic annealing of the cold rolled (90%) Zn-1.1%Al sheet specimens resulted in an asymmetry of the two major texture components. This effect is attributed to a magnetic driving force for grain growth. The grain microstructure evolution was also essentially affected by a magnetic field.

Mechanically Driven Migration of Tilt Grain Boundaries in Al-Bicrystals

2007 ◽  
Vol 558-559 ◽  
pp. 927-932 ◽  
Author(s):  
Dmitri A. Molodov ◽  
Tatiana Gorkaya ◽  
Günter Gottstein
Keyword(s):  
Grain Boundaries ◽  
Activation Enthalpy ◽  
Lateral Displacement ◽  
Boundary Migration ◽  
Activation Parameters ◽  
Boundary Mobility ◽  
Boundary Motion ◽  
Grain Boundary Mobility ◽  
Normal Boundary ◽  
Misorientation Angles

The stress induced migration of planar grain boundaries in aluminium bicrystals was measured. Symmetrical <100> tilt grain boundaries with misorientation angles in the range between 5.7° and 17.8° were examined. Boundary migration under a shear stress was observed to be ideally coupled to the lateral translation of grains. The measured ratios of the normal boundary motion to the lateral displacement of grains are in an excellent agreement with the respective boundary geometry. The temperature dependence of grain boundary mobility was measured, and the corresponding activation parameters were determined. The activation enthalpy of boundary migration was found to be independent of misorientation angle in the investigated misorientation range and amounts to H=1.44 eV.

Mechanisms of New Orientation Formation during Recrystallization of Old Deformed Aluminium Bicrystals

2005 ◽  
Vol 495-497 ◽  
pp. 1249-1254 ◽  
Author(s):  
Henryk Paul ◽  
Julian H. Driver ◽  
Arnaud Lens
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Pure Aluminium ◽  
Local Orientation ◽  
Sample Heating ◽  
Orientation Mapping ◽  
Grain Orientations ◽  
Slip Planes

The crystallography of recrystallization nucleation has been investigated in channel-die deformed pure aluminium bicrystals with {100}<011>/{110}<001> and {100}<001>/{110}<001> orientations. The new grain orientations and misorientations were followed by systematic local orientation measurements using SEM and semi-automatic measurements in a TEM. In particular, orientation mapping combined with in-situ sample heating was used to investigate the formation and growth of new grains and their crystallographic orientation changes at very early stages of recrystallization. Grain boundary migration and ‘consumption’ of the as-deformed areas was always favoured along directions parallel to the traces of the {111} slip planes that had been most active during deformation. The orientations of the first formed nuclei were misoriented with respect to the orientations identified within the neighbouring deformed areas by α(<111>, <112>, or <100>)relations.

In situ atomistic observation of grain boundary migration subjected to defect interaction

2020 ◽  
Vol 199 ◽  
pp. 42-52 ◽  
Author(s):  
Q. Zhu ◽  
S.C. Zhao ◽  
C. Deng ◽  
X.H. An ◽  
K.X. Song ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Defect Interaction

Anisotropy of Grain Boundary Migration Observed in Situ by Synchrotron Radiation

2004 ◽  
Vol 467-470 ◽  
pp. 911-916 ◽  
Author(s):  
Václav Paidar ◽  
Pavel Lejček ◽  
M. Polcarová ◽  
J. Brádler ◽  
Alain Jacques
Keyword(s):  
Synchrotron Radiation ◽  
Grain Boundary ◽  
Moving Boundary ◽  
Elevated Temperatures ◽  
Rotation Axis ◽  
Boundary Migration ◽  
Crystal Defects ◽  
Grain Boundary Migration ◽  
Grain Boundary Motion

Grain boundary motion was studied in situ at elevated temperatures by x-ray topography using synchrotron radiation. In addition to the position of grain boundary, other crystal defects that may interact with the moving boundary were observed simultaneously. Two types of bicrystals with the [001] rotation axis were selected for the experiments, the first one with a high coincidence S5 misorientation of about 37° and the other one with no coincidence of two crystals for the misorientation of 45°. The geometrical differences between chosen bicrystals are examined and attention is also paid to faceting – local orientations of the boundary plane.

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