Relationship between carbon segregation and the carbide precipitation along grain boundary based on the structural unit model

An electron microscope structure image of a σ = 21/[111] tilt grain boundary in Au was obtained and atomic column positions identified to yield a structural unit model of the interface consisting of repeating polyhedron shapes. This result represents the smallest projected spacings at a grain boundary containing defect structures imaged by an electron microscope and interpreted atomistically.

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Effect of Grain Boundary Structure on Grain Boundary Diffusivities in the Au/Ag System

MRS Proceedings ◽

10.1557/proc-209-33 ◽

1990 ◽

Vol 209 ◽

Cited By ~ 4

Author(s):

Qing Ma ◽

R. W. Balluffi

Keyword(s):

Thin Film ◽

Grain Boundary ◽

Grain Boundaries ◽

Tilt Angle ◽

Structural Unit ◽

Boundary Structure ◽

Grain Boundary Structure ◽

Unit Model ◽

Tilt Boundaries ◽

Accumulation Method

ABSTRACTGrain boundary chemical diffusivities for a series of symmetric [001] tilt boundaries in the Au/Ag system were measured by the surface accumulation method using newly developed thin-film multi-crystal specimens, in which the grain boundaries feeding the accumulation surface were all of the same type. Possible effects due to segregation at the grain boundaries and surfaces were avoided. CSL boundaries of low-Σ ( i.e., 5, 13, 17, 25) and also more general boundaries with tilt angles between the low-Σ orientations were selected. The diffusivities were found to vary monotonically with tilt angle ( i.e., no cusps at low-Σ's were found) in a manner consistent with the Structural Unit model.

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Computer simulation on surfaces and [001] symmetric tilt grain boundaries in Ni, Al, and Ni3Al

Journal of Materials Research ◽

10.1557/jmr.1989.0062 ◽

1989 ◽

Vol 4 (1) ◽

pp. 62-77 ◽

Cited By ~ 151

Author(s):

S. P. Chen ◽

D. J. Srolovitz ◽

A. F. Voter

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Structural Unit ◽

Boundary Energy ◽

Boundary Structure ◽

Grain Boundary Energy ◽

Local Composition ◽

Embedded Atom ◽

Grain Boundary Structure ◽

Unit Model

We have used “local volume” (embedded atom) type potentials to study the surfaces and grain boundaries of Ni, Al, and Ni3Al. The simulations show that with appropriately fit potentials, the surface and grain boundary structure can be realistically calculated. The surface rippling and relaxation show good agreement with experiments. The energies of most surfaces and grain boundaries also agree with existing data. The structural unit model for grain boundaries in Ni3Al shows the same generic units as in pure metals, but with large variations due to distortions and multiplicity. The utility of the structural unit model is thus more limited for alloys. The grain boundary energies were found to be the highest for Al-rich Ni3Al grain boundaries, and depend significantly on the local composition of the grain boundary. The cusps in the grain boundary energy as a function of misorientation angle are different for different grain boundary stoichiometries. The Ni3Al grain boundaries have approximately the same grain boundary energy and cohesive energy as that of Ni.

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The grain-boundary structural unit model redux

Acta Materialia ◽

10.1016/j.actamat.2017.05.002 ◽

2017 ◽

Vol 133 ◽

pp. 186-199 ◽

Cited By ~ 27

Author(s):

Jian Han ◽

Vaclav Vitek ◽

David J. Srolovitz

Keyword(s):

Grain Boundary ◽

Structural Unit ◽

Unit Model

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On the structural unit model of grain boundary structure

Philosophical Magazine Letters ◽

10.1080/09500838908214777 ◽

1989 ◽

Vol 59 (2) ◽

pp. 53-59 ◽

Cited By ~ 39

Author(s):

A. P. Sutton

Keyword(s):

Grain Boundary ◽

Structural Unit ◽

Boundary Structure ◽

Grain Boundary Structure ◽

Unit Model

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Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087331 ◽

1991 ◽

Vol 49 ◽

pp. 604-605

Author(s):

A.H. Advani ◽

L.E. Murr ◽

D. Matlock

Keyword(s):

Heat Treatment ◽

Grain Boundary ◽

Stress Corrosion Cracking ◽

Stainless Steels ◽

Deformation Twin ◽

Austenitic Stainless Steels ◽

Carbide Precipitation ◽

Strain Induced Martensite ◽

Type 304

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.

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