Molecular dynamics study of migration mechanism of triple junctions of tilt boundaries in fcc metals

Полетаев, Г. М.; Zorya, I. V.; Rakitin, R. Yu.

doi:10.1016/j.commatsci.2018.02.047

Cited by 20 publications

(11 citation statements)

References 17 publications

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“…3 a and 3 b). The analogy of the migration mechanisms of <110> boundaries with the mechanisms of migration of <111> and <100> boundaries considered earlier in [7,8] is clearly visible. During migration, in the grain towards which the migration took place, regions of the same shape orderly rotated through the angle of misorientation were formed, the size of which, in the case of low-angle boundaries, depended on the distance between neighboring grain boundary dislocations.…”

Section: Resultsmentioning

confidence: 61%

“…Low-angle <110> tilt boundaries are unique compared to other tilt boundaries -grain boundary dislocations at such boundaries are ordinary perfect edge dislocations with straight cores that do not contain jogs (or steps) on them. At the tilt boundaries with other misorientation axes, for example <111> and <100>, grain boundary dislocations are more complex, they are, as a rule, paired (i. e. dislocations from two sets with different slip planes combined in one core) and contain obligatory jogs along the cores [7,8]. Dislocations in <110> tilt boundaries do not have jogs and are relatively very mobile, which makes them unique.…”

Section: Resultsmentioning

confidence: 99%

“…Previously in [7,8], we have studied the atomic mechanism of migration of tilt boundaries with <100> and <111> misorientation axes, as well as their triple junctions, using the molecular dynamics method. It was shown that the migration and elongation of the low-angle <100> boundaries are occurred by splitting of the paired grain boundary dislocations with the subsequent change of the dislocationspartners.…”

Section: Introductionmentioning

confidence: 99%

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Migration mechanism of <110> tilt boundaries in nickel

2020

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The features and migration mechanism of tilt boundaries with the misorientation axis <110> in an fcc crystal using nickel as an example were studied by the method of molecular dynamics. The dependences of the boundaries energy and the rate of their migration at a temperature of 1700 K on the misorientation angle are obtained. It is shown that the migration rate of <110> tilt boundaries under the same conditions is an order of magnitude lower than the migration rate of <111> and <100> boundaries, which is primarily due to the relatively low energy of <110> boundaries. In addition, the low-angle <110> tilt boundaries are unique compared to other tilt boundaries-grain boundary dislocations in them are ordinary perfect edge dislocations with straight cores that do not contain jogs periodically located on them, as in <111> and <100> boundaries. In <110> boundaries, as well as in <111> and <100> boundaries, there are two different sets of dislocations, but they are not always combined, as is often the case in <111> and <100> boundaries. Combined dislocations in <110> boundaries turned out to be less mobile during boundary migration than non-combined ones. An analogy of migration mechanisms of low-angle <110> boundaries with the previously considered <111> and <100> boundaries was noted. During migration, in the grain towards which the migration took place, regions of the same shape orderly rotated through the angle of misorientation were formed, the size of which depended on the distance between neighboring grain boundary dislocations.

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Section: Resultsmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Migration mechanism of <110> tilt boundaries in nickel

2020

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“…The former are characterized by a periodic distribution of free volume, while the latter -by a continuous one. Low-angle tilt boundaries, as is known, are periodically located edge dislocations [17,19,22], while it is not possible to distinguish them at high-angle ones.…”

Section: Resultsmentioning

confidence: 99%

Modeling the formation of free volume at grain boundaries and triple junctions during nickel crystallization

et al. 2020

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The molecular dynamics method was used to study the formation of free volume at grain boundaries and triple junctions during crystallization using nickel as an example. To simulate the crystallization process, crystalline nuclei were used-small ideal crystals with a fixed lattice. The orientation of the crystal lattice in the nuclei was set randomly, but so that tilt boundaries with the misorientation axis <100> or <111> were formed in the result of crystallization. It is shown that the free volume during crystallization is predominantly concentrated at grain boundaries and triple junctions, and more so in the latter ones, i. e. where the last solidification of the structure occurs and crystallization fronts are encountered. The reduced density of the structure at triple junctions compared with grain boundaries is explained by the fact that when three crystallization fronts meet, the volume is fixed, where the liquid phase having a density lower than that of the crystal solidifies. The velocity of crystallization front motion is several tens of times lower than the speed of sound in a metal, therefore, defects, as a rule, formed only in the last turn-when the fronts meet, i. e. at grain boundaries and triple junctions. Disclinations at triple junctions were not observed in this work. During crystallization, relatively small subgrains with an orientation different from the neighboring grains, and usually in a stretched state, sometimes appeared in the region of triple junctions. But they "healed" relatively quickly, being absorbed by neighboring growing grains.

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“…On the other hand, the results of [5,6], on the contrary, indirectly support the predominance of the slip mechanism of grain-boundary dislocations. In [7,8], we have studied the atomic mechanism of migration of tilt boundaries with the <100> and <111> misorientation axes, as well as their triple junctions, using the molecular dynamics method. It is shown that the migration and elongation of the low-angle <100> boundaries is carried out by splitting of the paired grain boundary dislocations with the subsequent change of the dislocations-partners.…”

Section: Introductionmentioning

confidence: 99%

Effect of carbon and oxygen impurity atoms on the migration rate of tilt boundaries in fcc metals: a molecular dynamics simulation

et al. 2019

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The effect of carbon and oxygen impurity atoms on the migration rate of tilt boundaries with the <100> and <111> misorientation axes in fcc metals Ni, Ag, Al was studied by means of the molecular dynamics method. It is shown that the introduction of impurity atoms of light elements led to a significant inhibition of the migration of grain boundaries: with the introduction of 5 % by almost an order of magnitude, 10 % -by two orders of magnitude. Carbon atoms tend to form aggregates, which, being fixed on the grain boundary, become effective stoppers that prevent the boundary moving. Oxygen atoms did not form aggregates, but because of the high values of the binding energy with the boundaries, they also effectively hampered their migration. In contrast to the formation of aggregates by carbon atoms, in the case of oxygen impurity, another effect takes place -"loosening" and an increase in the width of the boundary. For impurity atoms of carbon and oxygen, the binding energies with grain-boundary edge dislocations in the metals under consideration were calculated. The obtained values correlate well with the dependences of the grain boundary migration rate on the impurity concentration: the greatest effect of impurities on the boundary migration rate and the value of the binding energy were obtained for the Al-C system, the smallest -for Ag-O.

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Molecular dynamics study of migration mechanism of triple junctions of tilt boundaries in fcc metals

Cited by 20 publications

References 17 publications

Migration mechanism of <110> tilt boundaries in nickel

Migration mechanism of <110> tilt boundaries in nickel

Modeling the formation of free volume at grain boundaries and triple junctions during nickel crystallization

Effect of carbon and oxygen impurity atoms on the migration rate of tilt boundaries in fcc metals: a molecular dynamics simulation

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