Grain boundary segregation in metals

1992 ◽  
Vol 50 (2) ◽  
pp. 1204-1205
Author(s):  
C.L. Briant
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Material Properties ◽  
Electron Spectroscopy ◽  
High Vacuum ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Local Concentration ◽  
The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

TEM study of grain boundary phase transformations in Cu-12 at PPM Bi polycrystals

1992 ◽  
Vol 50 (1) ◽  
pp. 210-211
Author(s):  
E.C. Urdaneta ◽  
C. J. McMahon ◽  
D. E. Luzzi
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Boundary Phase ◽  
Two Component ◽  
Fracture Surface Analysis ◽  
Bi Segregation

Grain boundary segregation-induced faceting is being studied in Cu-12 at ppm Bi polycrystals as a model two-component alloy for grain boundary transformations. It has been demonstrated that Bi segregation is responsible for grain boundary faceting in copper and that this transformation is reversible. Previous Auger electron spectroscopy fracture surface analysis in Bi-doped Cu have shown that grain boundary faceting only occurs after the segregated Bi reaches a saturation concentration of about 1 monolayer.

Atomic Scale Characterisation of Electrodeposited Nanocrystalline Ni-P Alloys

1999 ◽  
Vol 581 ◽  
Author(s):  
Matthias Abraham ◽  
Mattias Thuvandert ◽  
Helen M. Lane ◽  
Alfred Cerezo ◽  
George D.W. Smith
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Three Dimensional ◽  
Boundary Segregation ◽  
Atom Probe ◽  
Atomic Scale ◽  
Grain Boundary Segregation ◽  
P Concentration

ABSTRACTNanocrystalline Ni-P alloys produced by electrodeposition have been characterised by three-dimensional atom probe (3DAP) analysis. In the as-deposited materials, there are indications of some variation in P concentration between grains and segregation to grain boundaries. After heat treatment however, strong grain boundary segregation and the formation of Ni3P precipitates have been observed.

Fracture Modes in Ll2 Compounds

1988 ◽  
Vol 133 ◽  
Author(s):  
C. L. Briant ◽  
A. I. Taub
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Fracture Modes ◽  
Beneficial Effects ◽  
Boron Segregation ◽  
Total Composition ◽  
Carbon Additions

ABSTRACTThis paper reports a study of grain boundary segregation and fracture modes in Ll2 intermetallic compounds. Data obtained on Ni3A1, Ni3Si, Ni3Ga, Ni3Ge, and Pt3Ga will be presented. It will be shown that the amount of boron segregation and its ability to improve cohesion depends on the total composition of the compound. The beneficial effects of boron can be counteracted by the presence of borides on the grain boundaries. Carbon additions also produce some improvement in ductility in Ni3Si.

Grain-Boundary Segregation and Phase-Separation Mechanism in Yttria-Stabilized Tetragonal Zirconia Polycrystal

2011 ◽  
Vol 484 ◽  
pp. 82-88
Author(s):  
Koji Matsui ◽  
Hidehiro Yoshida ◽  
Yuichi Ikuhara
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Cubic Phase ◽  
Phase Boundaries ◽  
Transmission Electron ◽  
Sintering Condition

Microstructure development during sintering in 3 mol% Y2O3-stabilized tetragonal ZrO2 polycrystal (Y-TZP) was systematically investigated in two sintering conditions: (a) 1100-1650°C for 2 h and (b) 1300°C for 0-50 h. In the sintering condition (a), the density and grain size in Y-TZP increased with the increasing sintering temperature. Scanning transmission electron microscopy (STEM) and nanoprobe X-ray energy dispersive spectroscopy (EDS) measurements revealed that the Y3+ ion distribution was nearly homogeneous up to 1300°C, i.e., most of grains were the tetragonal phase, but cubic-phase regions with high Y3+ ion concentration were clearly formed in grain interiors adjacent to the grain boundaries at 1500°C. High-resolution transmission electron microscopy (HRTEM) and nanoprobe EDS measurements revealed that no amorphous or second phase is present along the grain-boundary faces, and Y3+ ions segregated not only along the tetragonal-tetragonal phase boundaries but also along tetragonal-cubic phase boundaries over a width below about 10 nm, respectively. These results indicate that the cubic-phase regions are formed from the grain boundaries and/or the multiple junctions in which Y3+ ions segregated. We termed this process a “grain boundary segregation-induced phase transformation (GBSIPT)” mechanism. In the sintering condition (b), the density was low and the grain-growth rate was much slow. In the specimen sintered at 1300°C for 50 h, the cubic-phase regions were clearly formed in the grain interiors adjacent to the grain boundaries. This behavior shows that the cubic-phase regions were formed without grain growth, which can be explained by the GBSIPT model.

Structure And Composition Of Grain Boundaries In SrTiO3

1999 ◽  
Vol 5 (S2) ◽  
pp. 94-95
Author(s):  
O. Kienzle ◽  
F. Ernst ◽  
Manfred Rühle
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Point Defects ◽  
Coincidence Site Lattice ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Boundary Structure ◽  
Dopant Atoms ◽  
Charged Point ◽  
Atomistic Structure

The electrical properties of SrTiO3 (strontium titanate) ceramics are strongly influenced or even dictated by grain boundary segregation of charged point defects, such as dopant atoms, impurities, vacancies, or self-interstitials. The atomistic structure of the grain boundaries, their energy, and the segregation of point defects mutually depend on each other. Grain boundary segregation of charged point defects induces the formation of space charge layers in the adjoining crystals. In order to investigate the relation between grain boundary structure and composition, grain boundaries in Fedoped SrTiO3 bicrystals and in SrTiO3 ceramics were studied by HRTEM and by AEM with subnanometer resolution.Quantitative HRTEM served to investigate the atomistic structure of Σ=3, (111) grain boundaries in Fe-doped SrTiO3 bicrystals with a doping level of Fe/Ti= 0.04at% (Fig. 1). Analysis of the translation state revealed that the Σ=3, (111) grain boundary has an excess volume: normal to the boundary plane, the spacing between the two crystals exceeds what one would expect from a coincidence site lattice model by (0.06 ±0.01 )nm.

Sign in / Sign up

Export Citation Format

Share Document