scholarly journals Grain Growth in Polar Ice: I. Theory

1986 ◽  
Vol 32 (112) ◽  
pp. 415-424 ◽  
Author(s):  
R. B. Alley ◽  
J.H. Perepezko ◽  
C.R. Bentley
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
High Velocity ◽  
Driving Force ◽  
Polar Ice ◽  
Low Velocity ◽  
Cross Sectional ◽  
Glacial Ice ◽  
Boundary Velocity ◽  
Velocity Characteristic

AbstractMany observations regarding grain growth in ice sheets are glaciologically interesting but imperfectly understood. Here we develop the theory of grain growth in ice that is not deforming rapidly, and in the succeeding paper we use this theory to explain observations from glacial ice. In the absence of significant strain energy, the driving force for grain growth arises from grain-boundary curvature. Grain growth is slowed by the interaction of grain boundaries with extrinsic materials (microparticles, bubbles, and dissolved impurities). If the driving force for growth is not large enough to cause boundaries to separate from an extrinsic material, then the grain-boundary velocity is determined by the velocity characteristic of the extrinsic material (low-velocity regime). If the driving force is large enough to cause separation, then boundaries migrate more rapidly than the extrinsic material (high-velocity regime) but the net driving force is reduced through transient pinning by the extrinsic material. Polar ice is typically in the low-velocity regime relative to dissolved impurities and the high-velocity regime relative to microparticles and bubbles. Cross-sectional area of grains is predicted to increase linearly with time under most but not all circumstances.

scholarly journals Grain Growth in Polar Ice: I. Theory

1986 ◽  
Vol 32 (112) ◽  
pp. 415-424 ◽  
Author(s):  
R. B. Alley ◽  
J.H. Perepezko ◽  
C.R. Bentley
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
High Velocity ◽  
Driving Force ◽  
Polar Ice ◽  
Low Velocity ◽  
Cross Sectional ◽  
Glacial Ice ◽  
Boundary Velocity ◽  
Velocity Characteristic

AbstractMany observations regarding grain growth in ice sheets are glaciologically interesting but imperfectly understood. Here we develop the theory of grain growth in ice that is not deforming rapidly, and in the succeeding paper we use this theory to explain observations from glacial ice. In the absence of significant strain energy, the driving force for grain growth arises from grain-boundary curvature. Grain growth is slowed by the interaction of grain boundaries with extrinsic materials (microparticles, bubbles, and dissolved impurities). If the driving force for growth is not large enough to cause boundaries to separate from an extrinsic material, then the grain-boundary velocity is determined by the velocity characteristic of the extrinsic material (low-velocity regime). If the driving force is large enough to cause separation, then boundaries migrate more rapidly than the extrinsic material (high-velocity regime) but the net driving force is reduced through transient pinning by the extrinsic material. Polar ice is typically in the low-velocity regime relative to dissolved impurities and the high-velocity regime relative to microparticles and bubbles. Cross-sectional area of grains is predicted to increase linearly with time under most but not all circumstances.

scholarly journals The Influence of Mg-Based Inclusions on the Grain Boundary Mobility of Austenite in SS400 Steel

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 370
Author(s):  
Chih-Ting Lai ◽  
Hsuan-Hao Lai ◽  
Yen-Hao Su ◽  
Fei-Ya Huang ◽  
Chi-Kang Lin ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
High Temperatures ◽  
Growth Curves ◽  
Solute Drag ◽  
Grain Structure ◽  
Growth Equation ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Boundary Velocity

In this study, the effects of the addition of Mg to the grain growth of austenite and the magnesium-based inclusions to mobility were investigated in SS400 steel at high temperatures. A high-temperature confocal scanning laser microscope (HT-CSLM) was employed to directly observe, in situ, the grain structure of austenite under 25 torr Ar at high temperatures. The grain size distribution of austenite showed the log-normal distribution. The results of the grain growth curves using 3D surface fitting showed that the n and Q values of the growth equation parameters ranged from 0.2 to 0.26 and from 405 kJ/mole to 752 kJ/mole, respectively, when adding 5.6–22 ppm of Mg. Increasing the temperature from 1150 to 1250 °C for 20 min and increasing the addition of Mg by 5.6, 11, and 22 ppm resulted in increases in the grain boundary velocity. The effects of solute drag and Zener pinning on grain boundary mobility were also calculated in this study.

scholarly journals Grain Growth and Mechanical Behaviour of Polar Ice

1985 ◽  
Vol 6 ◽  
pp. 79-82 ◽  
Author(s):  
P. Duval
Keyword(s):  
Crystal Growth ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Migration ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Polar Ice ◽  
Dislocation Glide ◽  
Ice Caps ◽  
Polar Snow

Crystal size in polar ice caps increases with depth from the snow surface down to several hundred meters. Data on crystal growth in isothermal polar snow and ice show the same linear relationship between the size of crystals and their age. This paper reviews the mechanical behavior of polar ice which exhibits grain growth. Grain boundary migration associated with grain growth appears to be an efficient accomodation process for grain boundary sliding and dislocation glide. For grain growth to occur, strain energy must always be lower than the free energy of boundaries. The sintering of ice particles in polar firn is energized by the pressure due to the overburden of snow. Dislocation creep must be taken into account to explain the densification rate in the intermediate and final stage Constants of power law creep should depend on the crystal growth rate.

scholarly journals Deformation and recrystallization processes of ice from polar ice sheets

2000 ◽  
Vol 30 ◽  
pp. 83-87 ◽  
Author(s):  
Paul Duval ◽  
Laurent Arnaud ◽  
Olivier Brissaud ◽  
Maureen Montagnat ◽  
Sophie de la Chapelle
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Migration ◽  
Ice Sheets ◽  
Ice Cores ◽  
Grain Boundary Sliding ◽  
Tertiary Creep ◽  
Dislocation Slip ◽  
Polar Ice ◽  
Polar Ice Sheets

AbstractInformation on deformation modes, fabric development and recrystallization processes was obtained by study of deep ice cores from polar ice sheets. It is shown that intracrystalline slip is the main deformation mechanism in polar ice sheets. Grain-boundary sliding does not appear to be a significant deformation mode. Special emphasis was laid on the occurrence of "laboratory" tertiary creep in ice sheets. The creep behavior is directly related to recrystallization processes. Grain-boundary migration associated with grain growth and rotation recrystallization accommodates dislocation slip and counteracts strain hardening. The fabric pattern is similar to that induced only by slip, even if rotation recrystallization slows down fabric development. Fabrics which develop during tertiary creep, and are associated with migration recrystallization, are typical recrystallization fabrics. They are associated with the fast boundary migration regime as observed in temperate glaciers. A decrease of the stress exponent is expected from 3, when migration recrystallization occurs, to a value ≤ 2 when normal grain growth occurs.

scholarly journals A mesoscopic approach for modelling texture evolution of polar ice including recrystallization phenomena

2003 ◽  
Vol 37 ◽  
pp. 23-28 ◽  
Author(s):  
Günter Gödert
Keyword(s):  
Grain Boundary ◽  
Texture Evolution ◽  
Boundary Migration ◽  
Volume Averaging ◽  
Texture Development ◽  
Order Structure ◽  
Grain Boundary Migration ◽  
Polar Ice ◽  
Low Velocity ◽  
Diffusion Type

AbstractA material model for the simulation of anisotropic behaviour due to texture development in polar ice is presented. Emphasis is laid on the strain-induced texture development and its relaxation due to rotation recrystallization and grain boundary migration in the low-velocity regime. The model is based on two scales (mesoscopic approach). Kinematics, balance equations and constitutive assumptions are defined with respect to the grain level (mesoscale). Slip-system behaviour is assumed to be Newtonian. Recrystallization and grain boundary migration are taken into account via a diffusion-type evolution of the crystallites orientation. Due to the inextensibility of the ice crystallites along their c axes, the Sachs–Reuss assumption is adopted. Volume averaging yields associated macroscopic relations, where the internal structure is represented by a second-order structure tensor. The proposed approach is illustrated by applying it to initially isotropic material under homogeneous deformation, giving results qualitatively in agreement with experimental evidence. Finally, it is shown that the proposed model is, under some simplifying conditions, directly related to phenomenological internal variable models (e.g. Morland and Staroszczyk, 1998).

Magnetically Driven Selective Grain Growth in Locally Deformed Zn Single Crystals

2004 ◽  
Vol 467-470 ◽  
pp. 763-770 ◽  
Author(s):  
P.J. Konijnenberg ◽  
Dmitri A. Molodov ◽  
Günter Gottstein
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Grain Growth ◽  
Driving Force ◽  
Grain Orientation ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
Single Temperature ◽  
Individual Grains

In magnetically anisotropic materials a driving force for grain boundary migration can be induced by an external magnetic ¯eld. It is experimentally shown that annealing of locally deformed Zn single crystals in a suitably directed high magnetic ¯eld results in a growth of new individual grains. Velocities of some solitary moving grain boundaries were measured and their absolute mobilities were estimated at a single temperature. Results are discussed in terms of preferential grain orientation and boundary character.

scholarly journals Computer simulation of grain growth kinetics with solute drag

1999 ◽  
Vol 14 (3) ◽  
pp. 1113-1123 ◽  
Author(s):  
D. Fan ◽  
S. P. Chen ◽  
Long-Qing Chen
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Growth Kinetics ◽  
Driving Force ◽  
Boundary Energy ◽  
Solute Drag ◽  
Lattice Diffusion ◽  
Diffuse Interface ◽  
Growth Exponent ◽  
Grain Growth Kinetics

The effects of solute drag on grain growth kinetics were studied in two-dimensional (2D) computer simulations by using a diffuse-interface field model. It is shown that, in the low velocity/low driving force regime, the velocity of a grain boundary motion departs from a linear relation with driving force (curvature) with solute drag. The nonlinear relation of migration velocity and driving force comes from the dependence of grain boundary energy and width on the curvature. The growth exponent m of power growth law for a polycrystalline system is affected by the segregation of solutes to grain boundaries. With the solute drag, the growth exponent m can take any value between 2 and 3, depending on the ratio of lattice diffusion to grain boundary mobility. The grain size and topological distributions are unaffected by solute drag, which are the same as those in a pure system.

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.

scholarly journals The grain boundary mobility tensor

2020 ◽  
Vol 117 (9) ◽  
pp. 4533-4538 ◽  
Author(s):  
Kongtao Chen ◽  
Jian Han ◽  
Xiaoqing Pan ◽  
David J. Srolovitz
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Driving Force ◽  
Chemical Potential ◽  
Md Simulations ◽  
Stress Generation ◽  
Grain Boundary Mobility ◽  
Mobility Tensor ◽  
The Impact ◽  
Shear Coupling

The grain-boundary (GB) mobility relates the GB velocity to the driving force. While the GB velocity is normally associated with motion of the GB normal to the GB plane, there is often a tangential motion of one grain with respect to the other across a GB; i.e., the GB velocity is a vector. GB motion can be driven by a jump in chemical potential across a GB or by shear applied parallel to the GB plane; the driving force has three components. Hence, the GB mobility must be a tensor (the off-diagonal components indicate shear coupling). Performing molecular dynamics (MD) simulations on a symmetric-tilt GB in copper, we demonstrate that all six components of the GB mobility tensor are nonzero (the mobility tensor is symmetric, as required by Onsager). We demonstrate that some of these mobility components increase with temperature, while, surprisingly, others decrease. We develop a disconnection dynamics-based statistical model that suggests that GB mobilities follow an Arrhenius relation with respect to temperature T below a critical temperatureTcand decrease as1/Tabove it.Tcis related to the operative disconnection mode(s) and its (their) energetics. For any GB, which disconnection modes dominate depends on the nature of the driving force and the mobility component of interest. Finally, we examine the impact of the generalization of the mobility for applications in classical capillarity-driven grain growth. We demonstrate that stress generation during GB migration (shear coupling) necessarily slows grain growth and reduces GB mobility in polycrystals.

scholarly journals Competition between grain growth and grain-size reduction in polar ice

2011 ◽  
Vol 57 (205) ◽  
pp. 942-948 ◽  
Author(s):  
Jens Roessiger ◽  
Paul D. Bons ◽  
Albert Griera ◽  
Mark W. Jessell ◽  
Lynn Evans ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Migration ◽  
Boundary Energy ◽  
Ice Core ◽  
Size Reduction ◽  
Polar Ice ◽  
Average Grain Size ◽  
Log Normal

AbstractStatic (or ‘normal’) grain growth, i.e. grain boundary migration driven solely by grain boundary energy, is considered to be an important process in polar ice. Many ice-core studies report a continual increase in average grain size with depth in the upper hundreds of metres of ice sheets, while at deeper levels grain size appears to reach a steady state as a consequence of a balance between grain growth and grain-size reduction by dynamic recrystallization. The growth factorkin the normal grain growth law is important for any process where grain growth plays a role, and it is normally assumed to be a temperature-dependent material property. Here we show, using numerical simulations with the program Elle, that the factorkalso incorporates the effect of the microstructure on grain growth. For example, a change in grain-size distribution from normal to log-normal in a thin section is found to correspond to an increase inkby a factor of 3.5.

Sign in / Sign up

Export Citation Format

Share Document