scholarly journals Influence of Finite Mobilities of Triple Junctions on the Grain Morphology and Kinetics of Grain Growth

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 185
Author(s):  
Ernst Gamsjäger ◽  
Boris Gschöpf ◽  
Jiří Svoboda
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Triple Junction ◽  
Cell Model ◽  
Grain Morphology ◽  
Triple Junctions ◽  
Grain Sizes ◽  
Heat Treated ◽  
Niobium Microalloyed Steel ◽  
Kinetics Of

Grain boundary networks composed of equal microstructural elements were investigated in a recent paper. In this work a more complicated artificial grain topology consisting of one four-sided, two six-sided and one eight-sided grain is designed to further investigate the influence of grain boundary and triple junction mobilities on the kinetics of the system in more detail. Depending on the value of the equal mobility of all triple junctions, the initially square-shaped four-sided grain changes its shape to become more or less rectangular. This indicates that the grain morphology is influenced by the value of the mobility of the triple junctions. It is also demonstrated that a grain arrangement with low mobility triple junctions controlling the kinetics of grain growth enhances growth of the large eight-sided grains. In addition, grain growth is investigated for different values of mobilities of triple junctions and grain boundaries. A strong elongation of several grains is predicted by the modeling results for reduced mobilities of the microstructural grain boundary elements. The two-dimensional modeling results are compared to micrographs of a heat-treated titanium niobium microalloyed steel. This feature, namely the evolution of elongated grains, is observed in the micrograph due to the pinning effect of (Ti, Nb)C precipitates at elevated soaking temperatures of around 1100 °C. Furthermore, the experiments show that a broader distribution of the grain sizes occur at 1100 °C compared to soaking temperatures, where pinning due to precipitates plays a less prominent role. A widening of the distribution of the grain sizes for small triple junction mobilities is also predicted by the unit cell model.

Thermodynamics and Kinetics of 1D Structural Elements and Stability of Nanocrystalline Materials

2015 ◽  
Vol 5 ◽  
pp. 173-195
Author(s):  
Günter Gottstein ◽  
Lazar S. Shvindlerman
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Triple Junction ◽  
Nanocrystalline Materials ◽  
Triple Line ◽  
Second Phase ◽  
Structural Elements ◽  
Triple Junctions ◽  
Line Energy ◽  
The Impact

Grain boundary triple junctions are the structural elements of a polycrystal. Recently it was recognized that they can strongly impact the microstructural evolution, and therefore there engender new opportunities to control and to design the grain microstructure of fine-grained and nanocrystalline materials due to their effect on recovery, recrystallization and grain growth. The measurement of triple junction energy and mobility is thus of great importance. The line energy of a triple junction constructs an additional driving force of grain growth. Taking the triple line energy into account, a modified form of the Zener force and the Gibbs-Thomson relation can be derived to reveal the influence of the triple line energy on second phase particles and the change of the equilibrium concentration of vacancies in the vicinity of voids at a grain boundary. The impact of triple junctions on the sintering of nanopowders is discussed. The role of “grain boundary - free surface” triple lines in the adhesive contact formation between spherical nanoparticles is considered. It is shown that there is a critical value of the triple line energy above which the nanoparticles do not stick together. Based on this result, a new nanoparticle agglomeration mechanism is proposed, which accounts for the formation of large agglomerates of crystallographically aligned nanoparticles during the nanopowder processing.

Triple Junction Controlled Grain Growth

2004 ◽  
Vol 467-470 ◽  
pp. 1093-1098 ◽  
Author(s):  
Vladimir Yu. Novikov
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Growth Kinetics ◽  
Triple Junction ◽  
Nanocrystalline Materials ◽  
Triple Junctions ◽  
Restricted Mobility ◽  
Triple Junction Mobility ◽  
Grain Diameter

Grain growth in 2D polycrystals was simulated under the supposition that triple junctions possess a restricted mobility and so impede the migration of grain boundaries. A parameter 0 L = 0 D m taking into account the effect of triple junctions was varied in the range from 0.003 to 270 (m is the ratio of the triple junction mobility to that of grain boundary and 0 D the initial grain diameter). It was shown that at 0 L <0.4–0.5, i.e. at a small 0 D and small m, the growth kinetics becomes linear. It is supposed that the effect of triple junctions on grain growth can be observed in nanocrystalline materials.

scholarly journals Kinetics of Grain Boundary Networks Controlled by Triple Junction and Grain Boundary Mobility

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 977 ◽  
Author(s):  
Ernst Gamsjäger ◽  
Daniel Ogris ◽  
Jiří Svoboda
Keyword(s):  
Analytical Solution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Triple Junction ◽  
Irreversible Thermodynamics ◽  
Force Balance ◽  
Structural Elements ◽  
Grain Boundary Mobility ◽  
Kinetics Of

The kinetics of a triple junction of grain boundaries with distinct specific energies and mobilities and a finite mobility of the triple junction is investigated. The microstructure is approximated by different 2D settings consisting of typical structural elements. First, the migration of the triple point together with the adjacent grain boundaries, is simulated, assuming that the grains are infinitely large. Secondly, growth or shrinkage of finite n-sided grains is simulated by altering the boundary conditions and the results are compared to the already published analytical solution. The numerical results coincide with the corrected analytical solution. This solution can be derived either by applying the principle of maximum dissipation, or by applying the force balance at the triple junction within the framework of linear irreversible thermodynamics. The change of the area of infinite and finite grains is investigated analytically and numerically. By comparing the results of both approaches, the influence of the initial topology of the structural elements on the kinetics of grain growth can be estimated. Furthermore, the kinetics of grain growth of different idealized grain boundary networks is investigated. It is shown that square shaped grains surrounded by hexagons and dodecagons result in a more realistic grain growth scenarios than squares surrounded by octagons. A deviation from idealized grain boundary arrangements is e.g., observed, due to different triple junction mobilities, and the initially n-sided regular grain deforms in a complex manner.

The Effect of Variability Among Grain Boundary Energies on Grain Growth in Thin Film Strips

1994 ◽  
Vol 338 ◽  
Author(s):  
H.J. Frost ◽  
Y. Hayashi ◽  
C.V. Thompson ◽  
D.T. Walton
Keyword(s):  
Thin Film ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Energy ◽  
Strip Width ◽  
Grain Boundary Energy ◽  
Triple Junctions ◽  
Interconnect Reliability ◽  
Bamboo Structure ◽  
Grain Boundary Pinning

ABSTRACTGrain growth in thin-film strips is important to interconnect reliability because grain boundary structures strongly effect the rate and mechanism of electromigration-induced failure. Previous simulations of this process have indicated that the transformation to the fully bamboo structure proceeds at a rate which decreases exponentially with time, and which is inversely proportional to the square of the strip width. We have also reported that grain boundary pinning due to surface grooving implies that there exists a maximum strip width to thickness ratio beyond which the transformation to the bamboo structure does not proceed to completion. In this work we have extended our simulation of grain growth in thin films and thin film strips to consider the effects of variations in grain boundary energy. Boundary energy is taken to depend on the misorientation between the two neighboring grain and the resulting variations in grain boundary energy mean that dihedral angles at triple junctions deviate from 120°. The proportionality between boundary velocities and local curvatures, and the critical curvature for boundary pinning due to surface grooving also both depend on boundary energy. In the case of thin-film strips, the effect of boundary energy variability is to impede the transformation to the bamboo structure, and reduce the width above which the complete bamboo structure is never reached. Those boundaries which do remain upon stagnation tend to be of low energy (low misorientation angle) and are therefore probably of low diffusivity, so that their impact on reliability is probably reduced.

Diffusion Mechanisms in Nanocrystalline and Nanolaminated Au-Cu

2007 ◽  
Vol 266 ◽  
pp. 13-28 ◽  
Author(s):  
Alan F. Jankowski
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Bulk Diffusion ◽  
Grain Boundary Diffusion ◽  
Dominant Mechanism ◽  
Temperature Range ◽  
Diffusion Mechanisms ◽  
Kinetics Of

Thermal anneal treatments are used to identify the temperature range of the two dominant diffusion mechanisms – bulk and grain boundary. To assess the transition between mechanisms, the low temperature range for bulk diffusion is established utilizing the decay of static concentration waves in composition-modulated nanolaminates. These multilayered structures are synthesized using vapor deposition methods as thermal evaporation and magnetron sputtering. However, at low temperature the kinetics of grain-boundary diffusion are much faster than bulk diffusion. The synthesis of Au-Cu alloys (0-20 wt.% Cu) with grain sizes as small as 5 nm is accomplished using pulsed electro-deposition. Since the nanocrystalline grain structure is thermally unstable, these structures are ideal for measuring the kinetics of grain boundary diffusion as measured by coarsening of grain size with low temperature anneal treatments. A transition in the dominant mechanism for grain growth from grain boundary to bulk diffusion is found with an increase in temperature. The activation energy for bulk diffusion is found to be 1.8 eV·atom-1 whereas that for grain growth at low temperatures is only 0.2 eV·atom-1. The temperature for transitioning from the dominant mechanism of grain boundary to bulk diffusion is found to be 57% of the alloy melt temperature and is dependent on composition.

Topological Stability of 2-D Vanishing Grains

1992 ◽  
Vol 278 ◽  
Author(s):  
V. E. Fradkov ◽  
M. E. Glicksman ◽  
J. Nordberg ◽  
M. Palmer ◽  
K. Rajan
Keyword(s):  
Computer Simulation ◽  
Grain Boundary ◽  
Grain Growth ◽  
Triple Junctions ◽  
Polycrystalline Films ◽  
Topological Stability ◽  
Von Neumann ◽  
Small Grains ◽  
The Mean ◽  
Boundary Model

AbstractGrain growth in polycrystals occurs by decreasing the total number of grains as a result of the disappearance of small ones. That is why the both the kinetic and topological details of shrinking of small grains are important.In 2-D, “uniform boundary model” assumptions imply the von Neumann-Mullins law, and all grains having less than 6 neighbors tend to shrink. The mean topological class ef vanishing grains was found experimentally to be about 4.3. This result suggests that most vanishing grains are either 4- or 5-sided, not transforming to 3-sided ones.Shrinking of 4- and 5-sided 2-D grains was studied experimentally on transparent, pure SCN, (succinonitrile) polycrystalline films and by direct computer simulation of grain boundary capillary motion together with triple junctions. It was found that the grains which are much smaller than their neighbors are topologically stable.

New Understanding of Abnormal Grain Growth Approached by Solid-State Wetting along Grain Boundary or Triple Junction

2004 ◽  
Vol 467-470 ◽  
pp. 745-750 ◽  
Author(s):  
Nong Moon Hwang
Keyword(s):  
Solid State ◽  
Grain Boundary ◽  
Grain Growth ◽  
Triple Junction ◽  
Boundary Energy ◽  
Growth Front ◽  
Abnormal Grain Growth ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Mc Simulation

Although it has been generally believed that the advantage of the grain boundary mobility induces abnormal grain growth (AGG), it is suggested that the advantage of the low grain boundary energy, which favors the growth by solid-state wetting, induces AGG. Analyses based on Monte Carlo (MC) simulation show that the approach by solid-state wetting could explain AGG much better than that by grain boundary mobility. AGG by solid-state wetting is supported not only by MC simulations but also by the experimental observation of microstructure evolution near or at the growth front of abnormally growing grain. The microstructure shows island grains and solid-state wetting along grain boundary and triple junction.

Effects of Triple Line Tension on the Surface Topography of Polycrystals

2002 ◽  
Vol 731 ◽  
Author(s):  
Jon L. Hilden ◽  
Alexander H. King
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Triple Line ◽  
Line Tension ◽  
Triple Junctions ◽  
Polycrystalline Thin Film ◽  
Surface Evolver ◽  
Grain Sizes ◽  
Solid Specimen ◽  
Numerical Software

AbstractA balance of surface energies exists where grain boundaries meet the surface of a flat solid specimen. The energy balance leads to grain boundary grooving on the surface, and the establishment of the equilibrium dihedral angle. Triple junctions are defined at the intersections of three grain boundaries. Surface grooves are typically observed to be the deepest at the triple junctions. In this work, a simple model is constructed of a polycrystalline thin film using Surface Evolver numerical software. The equilibrium sur face groove depths at triple junctions are investigated as a function of triple junction line tension. Results show that line tension can affect grain boundary groove depths for grain sizes less than ∼1μm.

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