Grain boundary diffusion mechanisms in metals

Balluffi, R. W.; Mehl, R. F.

doi:10.1007/bf02648378

Cited by 189 publications

(75 citation statements)

References 56 publications

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“…In metals grain boundary diffusion has been studied more widely than in ceramics and is reasonably well understood [1,2]. As far as the authors are aware grain boundary diffusion is always much faster than bulk diffusion in metals and is typified by the summary for fcc metals shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Grain Boundary Diffusion in Ceramics

Atkinson

Monty²

1989

Surfaces and Interfaces of Ceramic Materials

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ABSTRACT. Diffusion at a grain boundary occurs at a different rate from that in the bulk crystalline lattice. Usually bulk lattice diffusion is relatively slow and boundary diffusion is much more rapid so that the boundary acts as an easy (or short circuit) path for transport in parallel with bulk diffusion.The experimental approaches to direct measurement of tracer diffusion along grain boundaries are well-established and, in principle, can give the grain boundary diffusion coefficient and the grain boundary width (or, in the case of an impurity atom, the product of boundary width and the segregation coefficient).Published data cover a range of materials in doped and undoped forms, and specimen types (single crystals, bicrystals, sintered powders and thin films), with host atoms or impurities as the diffusing species. In addition, atomistic simulations have been carried out using static lattice methods to help interpret the experimental observations. There is much disagreement in the detailed results in this field, but certain general conclusions are emerging.

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Section: Introductionmentioning

confidence: 99%

Grain Boundary Diffusion in Ceramics

Atkinson

Monty²

1989

Surfaces and Interfaces of Ceramic Materials

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“…Adiabatic shear bands are generated by strain localization and temperature rise due to plastic instability at impacted regions, and work as a critical factor abruptly reducing impact resistance. [1][2][3][4][5][6][7][8][9] Thus, research on how to remove or prevent the formation of adiabatic shear bands is demanded for the development of Ti-6Al-4V alloy for armor plates.…”

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confidence: 99%

“…Grain boundary diffusion has been shown to depend on the grain boundary structure, which also impacts their effectiveness as vacancy sinks and sources. [6][7][8][9][10] Coincident site lattice boundaries (CSLBs) have been shown to be more resistant to creep fracture under conditions where grain boundary diffusivity controls creep. [5] When power law creep is dominant, CSLBs will affect creep through dislocation adsorption as described by Thaveeprunsriporn and Was.…”

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confidence: 99%

Grain boundary engineering of ferritic-martensitic alloy T91

Gupta

Was

Alexandreanu

2004

Metall Mater Trans A

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Ferritic-martensitic alloys such as T91 are proposed for applications in high-temperature, advanced nuclear reactor core materials applications where tolerance to radiation damage and retention of high-temperature strength and creep resistance are required. One strategy for improving creep resistance is via grain boundary structure engineering, in which the fraction of special boundaries is increased. Such increases in special boundaries have proven effective in reducing creep rates in ferritic and austenitic alloys. [1][2][3][4][5] Diffusional flow creep and power law creep are the two principal mechanisms of creep observed in alloy T91. Grain boundary diffusion has been shown to depend on the grain boundary structure, which also impacts their effectiveness as vacancy sinks and sources. [6][7][8][9][10] Coincident site lattice boundaries (CSLBs) have been shown to be more resistant to creep fracture under conditions where grain boundary diffusivity controls creep. [5] When power law creep is dominant, CSLBs will affect creep through dislocation adsorption as described by Thaveeprunsriporn and Was. [1] In either case, grain boundary structure engineering is expected to enhance creep strength of this alloy.Grain boundary structure engineering involves a series of thermomechanical treatments designed to increase the CSLB fraction. The CSL model refers to the two-dimensional superlattice that forms at certain angle-axis combinations at which a fraction of the lattice points from one crystal are superimposed on lattice points from the adjacent crystal. [11,12] The basic idea is to introduce a small amount of deformation into the sample either by compression or tension. A finite fraction of the energy expended in cold work is stored in the metal as strain energy associated with various lattice defects created by the deformation. The subsequent annealing step causes recovery and realignment of the grain boundary region into a lower energy state that reduces the mismatch between the boundaries of the grains and converts a fraction of the high-energy boundaries to low-energy boundaries. [13] Ferritic-martensitic alloys present a unique challenge due to their complicated microstructure. T91 is a low-carbon, 9Cr-1MoVNb steel that is used in the two-phase, ferriticmartensitic structure. The standard heat treatment consists of a solution anneal at 1066°C for 46 minutes to completely austenitize the microstructure and dissolve the carbides, and a tempering treatment of 790°C for 42 minutes to relieve the stresses and enhance toughness. The resulting microstructure ( Figure 1) consists of tempered martensitic laths forming subgrains in a ferrite matrix, with (V, Nb) carbonitrides precipitated mainly on dislocations within the subgrains and M 23 C 6 precipitated on the prior austenite grain boundaries and on subgrain boundaries. [14] The subgrain structure produced by martensitic transformation and the precipitation of carbides and carbonitrides are the primary microstructural features responsible for high-temperature creep str...

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“…GB can migrate with the translation of grains if the shear stress is applied on the metallic materials and such GB migration may be defined as the coupled motion [8][9][10]. The common GB migration without stress is dominated by the diffusion of vacancies [11], and the coupled motion of GB is dominated by the collective movement of atoms [12]. The coupled motion has a lower migration barrier and higher migration speed compared with the common GB migration.…”

Section: Introductionmentioning

confidence: 99%

Effect of hydrogen on grain boundary migration in tungsten

Shu

Liu

et al. 2015

Sci. China Phys. Mech. Astron.

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Motivated by a grain boundary (GB) healing mechanism that GB turns into a mobile sink through migration to eliminate the vacancies in a bulk, we have further investigated the influence of the retained hydrogen (H) on the GB migration in tungsten using a molecular dynamics simulation. We show that H hinders the GB migration at different H concentrations and temperatures, and such friction of GB migration due to the presence of H increases with the H concentration and decreases with temperature. We demonstrate that H follows the GB-migration as the temperature is higher than 300 K. Most importantly, the presence of H induces a disordering of GB, which affects the GB migration significantly. tungsten grain boundary, hydrogen, migration, molecular dynamics, disordering PACS number(s): 28.52.Fa, 61.72.Mm, 61.82.Bg, 31.15.Qg Citation: Yu Y, Shu X L, Liu Y N, et al. Effect of hydrogen on grain boundary migration in tungsten.

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Grain boundary diffusion mechanisms in metals

Cited by 189 publications

References 56 publications

Grain Boundary Diffusion in Ceramics

Grain Boundary Diffusion in Ceramics

Grain boundary engineering of ferritic-martensitic alloy T91

Effect of hydrogen on grain boundary migration in tungsten

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