Studies of Grain Boundary Structure in Pure Metals and Alloys by Combined X-Ray Diffraction and Computer Simulation

1993 ◽  
Vol 126-128 ◽  
pp. 25-34 ◽  
Author(s):  
P.D. Bristowe ◽  
I. Majid ◽  
C. Counterman ◽  
D. Wang ◽  
R.W. Ballufi
Keyword(s):  
Computer Simulation ◽  
Grain Boundary ◽  
Metals And Alloys ◽  
Boundary Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Boundary Structure ◽  
Pure Metals

On The Study Of Grain Boundary Segregation Using X-Ray Diffraction And Computer Simulation

1991 ◽  
Vol 238 ◽  
Author(s):  
C. A. Counterman ◽  
I. Majid ◽  
P. D. Bristowe ◽  
R. W. Balluffi
Keyword(s):  
Computer Simulation ◽  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Boundary Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Grain Boundary Structure ◽  
Structure Factors ◽  
Diffraction Effects

ABSTRACTThe possibility of studying grain boundary segregation using X-ray diffraction is explored by performing a computer simulation of the diffraction effects expected from the segregation of solute atoms to grain boundaries in two gold alloy systems, i.e. Au-Ag and Au-Ni. Using atomistic Monte-Carlo and molecular statics methods, equilibrium boundary structures are determined and analyzed by computing the grain boundary structure factors. Various changes in both relative and absolute grain boundary structure factors are found which can be directly related to structural and compositional changes due to segregation. In addition, systematic diffraction effects are found as a function of boundary misorientation. The experimental conditions required for verifying these predictions are discussed.

Effect of Thermomechanical Treatment on the Grain Boundary Structure in Pure Aluminum

1975 ◽  
Vol 33 ◽  
pp. 172-173
Author(s):  
Eswarahalli Venkatesh ◽  
L.E. Murr
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Thermomechanical Treatment ◽  
Pure Aluminum ◽  
Metals And Alloys ◽  
Boundary Structure ◽  
Air Cooling ◽  
Grain Boundary Structure ◽  
Cold Rolled ◽  
Pure Metals

In recent years, many researchers have shown great interest in understanding the structure of grain boundaries and their influence on the mechanical properties in metals and alloys. In recent years, the structure of grain boundaries and their control have been considered as a means of understanding the strengthening mechanisms in metals and alloys. There are many ways by which the grain boundary structure can be changed both in pure metals and alloys. One such means considered here is the thermomechanical treatment of pure metals.In the present work, high purity (99.9999%) aluminum sheet, mill rolled to 0.004 in. thick, is used. The as-received condition of the sample was flash-annealed at 903°K in an argon atmosphere. Batch specimens from this stock were cold rolled to 50% reduction in thickness and annealed in air at 903°K followed by either furnace cooling or air cooling to room temperature.

scholarly journals Characterization of Nanophase Materials by X-Ray Diffraction and Computer Simulation

1989 ◽  
Vol 153 ◽  
Author(s):  
J. A. Eastman ◽  
L. J. Thompson
Keyword(s):  
Computer Simulation ◽  
Grain Boundary ◽  
Interplanar Spacing ◽  
Structural Parameters ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanophase Materials ◽  
Boundary Width ◽  
Model Structures

AbstractX-ray diffraction experiments on nanophase Pd have been performed with the primary goal of determining the nature of grain boundary structures in nanophase materials. A kinematical diffraction analysis has been developed to interpret x-ray θ-2θ data by comparing actual scans with scans produced by computer simulation. This simulation program has been used to explore the effects on diffracted intensity of a variety of microstructural and grain boundary structural parameters such as void concentration, grain size, grain boundary width, and changes in interplanar spacing and density in grain boundary regions. It has been found that a reasonable match to experimental data is produced by at least two model structures; in one, the material contains randomly positioned voids or vacancies, while in the other, the interplanar spacings in grain boundary regions are varied with respect to the spacings found in the grain interiors.

Grain Boundary Structure and Deformation Defects in Nanostructured Al–Mg Alloys Processed by High Pressure Torsion

2008 ◽  
Vol 584-586 ◽  
pp. 528-534 ◽  
Author(s):  
M. Liu ◽  
Hans Jørgen Roven ◽  
Tamás Ungár ◽  
L. Balogh ◽  
Maxim Yu. Murashkin ◽  
...  
Keyword(s):  
High Pressure ◽  
Grain Boundary ◽  
Line Profile ◽  
High Pressure Torsion ◽  
Boundary Structure ◽  
X Ray ◽  
Grain Boundary Structure ◽  
Average Grain Size ◽  
Deformation Defects ◽  
Non Equilibrium

An Al–0.5 Mg alloy and a commercial AA5182 alloy were subjected to high pressure torsion (HPT) to five turns under pressure of 6 GPa at room temperature. The grain boundary structure and deformation defects were investigated after HPT using high-resolution transmission electron microscopy (HRTEM). Low-angle, high-angle, equilibrium and non-equilibrium grain/subgrain boundaries, twin boundaries, full dislocations, dipoles, microtwins and stacking faults were identified by HRTEM. Extrinsic 60° dislocations in the form of dipoles were frequently observed in non-equilibrium grain/subgrain boundaries. In addition subgrain size distributions and dislocation densities were quantified by x-ray line profile analysis. It was observed that the average grain size decreased from about 120 nm to 55 nm as the Mg content increased from 0.5 to 4.1 wt%. Concomitantly the average stored dislocation density increased from 1.7 to 12.8  1014 m-2. Based on the HRTEM investigations and the x-ray line profile analyses, the deformation mechanism associated with the typical grain boundaries and deformation defects in the aluminium alloys were discussed.

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

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.

Imaging of Magnetic Steel Filaments with an HB-5 STEM

1981 ◽  
Vol 39 ◽  
pp. 322-323
Author(s):  
I. Y. T. Chan ◽  
H. G. F. Wilsdorf
Keyword(s):  
Vapor Deposition ◽  
Chemical Vapor ◽  
Boundary Structure ◽  
X Ray Diffraction ◽  
Iron Carbides ◽  
Similar Composition ◽  
X Ray ◽  
Grain Boundary Structure ◽  
Ion Microscopy ◽  
Magnetic Steel

The tensile strength of polycrystalline steel filaments 0.2-0.6 cm long with diameters between 1 μm and 20μm can be as high as 8 GPa. When compared to steels of similar composition (α-Fe with 1.5 w/o C, 0.8 w/o O) obtained by solidification, they exhibit an exceptional microstructure due to their production by chemical vapor deposition in the presence of a strong magnetic field. Regardless of the diameter, the grain size is between 10 nm and 30 nm. TEM, field ion microscopy, electron and x-ray diffraction studies have shown that within the grains a microdispersion of iron oxides, iron carbides, and carbon exists. Also, it was found in a recent investigation that the boundaries between grains are not sharp and planar but consist of regions about 2 nm wide. The following research was aimed at clarifying the grain boundary structure.

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