Hardening effects of grain boundary defect structure

The grain boundary defect structure can be changed to advantage by appropriate mechanical and thermal treatments. Researchers continue to show interest in understanding the effects of boundary defect structure on the mechanical properties of polycrystalline metals and alloys. Grain boundary structural features such as boundary ledges have been considered as a means of strengthening in metals and alloys. Considering the various models of Hall-Petch analyses, the grain boundary strength, σg can be expressed as σg = 8αGb(l-υ)m(L/ℓ); where m is the grain boundary ledge density, L is the grain size, ℓ is the distance of dislocation source in the adjacent grain matrix from the boundary, and G, b, and υ have the usual meaning. In particular, the influence of grain boundary ledge density on the strength (hardness) of grain boundaries is considered in the present paper.In the present investigation, pure (99.98%) nickel sheet mill (hot) rolled to 0.022 in. thick was used.

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Effect of Grain Boundary Ledges on the Flow Stress in Nickel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078948 ◽

1977 ◽

Vol 35 ◽

pp. 284-285

Author(s):

Eswarahalli S. Venkatesh ◽

L.E. Murr

Keyword(s):

Flow Stress ◽

Grain Boundary ◽

Grain Boundaries ◽

Polycrystalline Materials ◽

Structure And Properties ◽

Boundary Dislocation ◽

Dislocation Source ◽

Type Relation ◽

Ledge Density ◽

Boundary Ledge

In a recent paper1 it was shown that grain boundary ledge structure can be changed by appropriate thermomechanical treatments. Grain boundary ledges are sources of dislocations2. Recently the effects of grain boundaries on the mechanical properties in metals and alloys were studied3,4. For a few years now the structure and properties of grain boundaries and their control have been considered as a means of strengthening polycrystalline materials5,6. Li5 has derived a Hall-Petch type relation in terms of grain boundary dislocation source (ledge) density, m, in the form where L is the grain size, σ0 and α are constants, and G ana b have the usual meaning. The influence of grain boundary ledge density, on the flow stress is considered in this paper.In the present work, pure (99.98%) nickel sheet mill rolled (hot) to 0.022 in. thick was used.

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Grain size dependent grain boundary defect structure: case of doped zirconia

Acta Materialia ◽

10.1016/s1359-6454(03)00052-1 ◽

2003 ◽

Vol 51 (9) ◽

pp. 2539-2547 ◽

Cited By ~ 128

Author(s):

Xin Guo ◽

Zaoli Zhang

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Defect Structure ◽

Size Dependent ◽

Boundary Defect

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Structure of Grain Boundaries in Metals and Alloys: Direct Observations in the TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070977 ◽

1973 ◽

Vol 31 ◽

pp. 106-107

Author(s):

L. E. Murr

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Small Angle ◽

Structural Features ◽

Metals And Alloys ◽

Boundary Structure ◽

Screw Dislocations ◽

Direct Observations ◽

Grain Boundary Structure

Many models of grain boundaries in metals and alloys have been developed in attempts to interpret their properties and observed structures. Because of the complexity of grain boundary structure, it is generally possible to apply any of the proposed models in any material, and to describe grain boundaries as possessing dislocation structures, ledges, protrusions, island structures, facets, coincidence regions which exhibit good atomic fit and establish a kind of superlattice array, and combinations of these structural features.The dislocation nature of small angle grain boundaries is well known, consisting of tilt or twist arrays or combinations of edge or screw dislocations.

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The influence of grain boundary ledge density on the flow stress in nickel

Materials Science and Engineering ◽

10.1016/0025-5416(78)90155-6 ◽

1978 ◽

Vol 33 (1) ◽

pp. 69-80 ◽

Cited By ~ 15

Author(s):

Eswarahalli S. Venkatesh ◽

Lawrence E. Murr

Keyword(s):

Flow Stress ◽

Grain Boundary ◽

Ledge Density ◽

Boundary Ledge

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Correlation of grain boundary defect structure with boundary orientation in Ba2YCu3O7−x

Applied Physics Letters ◽

10.1063/1.100502 ◽

1988 ◽

Vol 53 (21) ◽

pp. 2105-2107 ◽

Cited By ~ 21

Author(s):

S. Nakahara ◽

G. J. Fisanick ◽

M. F. Yan ◽

R. B. van Dover ◽

T. Boone

Keyword(s):

Grain Boundary ◽

Defect Structure ◽

Boundary Defect ◽

Boundary Orientation

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Metallurgical Effects of Grain Boundary Ledges

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078225 ◽

1977 ◽

Vol 35 ◽

pp. 126-129

Author(s):

L.E. Murr

Keyword(s):

Grain Boundary ◽

Quantitative Data ◽

Mechanical Treatment ◽

Unit Length ◽

Physical And Mechanical Properties ◽

Direct Observations ◽

Transmission Electron ◽

Properties Of Materials ◽

Thermo Mechanical Treatment ◽

Ledge Density

Ledges in grain boundaries can be identified by their characteristic contrast features (straight, black-white lines) distinct from those of lattice dislocations, for example1,2 [see Fig. 1(a) and (b)]. Simple contrast rules as pointed out by Murr and Venkatesh2, can be established so that ledges may be recognized with come confidence, and the number of ledges per unit length of grain boundary (referred to as the ledge density, m) measured by direct observations in the transmission electron microscope. Such measurements can then give rise to quantitative data which can be used to provide evidence for the influence of ledges on the physical and mechanical properties of materials.It has been shown that ledge density can be systematically altered in some metals by thermo-mechanical treatment3,4.

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Grain-Boundary Defect Chemistry of Acceptor-Doped Titanates: Inversion Layer and Low-Field Conduction

Journal of the American Ceramic Society ◽

10.1111/j.1151-2916.1997.tb03121.x ◽

2005 ◽

Vol 80 (9) ◽

pp. 2301-2314 ◽

Cited By ~ 101

Author(s):

Markus Vollmann ◽

Rainer Hagenbeck ◽

Rainer Waser

Keyword(s):

Grain Boundary ◽

Inversion Layer ◽

Defect Chemistry ◽

Low Field ◽

Boundary Defect

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Inspection Of Recombination Active Defects For Sige And Solar Cells

MRS Proceedings ◽

10.1557/proc-442-43 ◽

1996 ◽

Vol 442 ◽

Cited By ~ 3

Author(s):

O.V. Astafiev ◽

V.P. Kalinushkin ◽

N.V. Abrosimov

Keyword(s):

Solar Cells ◽

Solar Cell ◽

Light Scattering ◽

Grain Boundary ◽

Single Crystals ◽

Defect Structure ◽

Scattering Method ◽

Recombination Activity ◽

Cell Production ◽

Materials Used

AbstractMapping Low Angle Light Scattering method (MLALS) is proposed to study defect structure in materials used for solar cell production. Several types of defects are observed in Czochralski Si1−xGex (0.022<x<0.047) single crystals. Recombination activity of these defects is investigated. The possibility of contactless visualisation of grain boundary recombination in polysilicon is also demonstrated.

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