Interaction between planar lattice defects and migrating grain boundaries

1980 ◽  
Vol 59 (1) ◽  
pp. 163-170
Author(s):  
R. Pareja ◽  
J. Serna
Keyword(s):  
Grain Boundaries ◽  
Lattice Defects ◽  
Planar Lattice

Microstructures and Mechanical Property of Ni Processed by High-Pressure Torsion and Their Evolution upon Annealing

2006 ◽  
Vol 114 ◽  
pp. 45-50 ◽  
Author(s):  
Zhi Qing Yang
Keyword(s):  
High Pressure ◽  
Grain Boundaries ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Small Difference ◽  
Dynamical Evolution ◽  
Peripheral Region ◽  
Lattice Defects ◽  
Grain Sizes ◽  
Xrd And Tem

XRD, TEM, microhardness and thermal analysis were carried out on a series of Ni samples produced by high-pressure torsion (HPT). The evolution of microstructures and their inhomogeneity were investigated. The local microstrain showed dynamical oscillations as a function of the HPT rotations, demonstrating dynamical evolution of lattice defects during the procedure. Both XRD and TEM showed that a small difference in grain sizes remains even after 5 revolutions of HPT with smaller grain sizes at the peripheral region of the sample. The higher microhardness at the peripheral region is the result of the smaller grain sizes and the higher density of lattice defects, compared with the central region. Thermal treatment at a heating rate of 20K/min from room temperature to 473K did not result in decreased microhardness, but increased by about 10% for samples treated with not more than 3 rotations of HPT. The increase in microhardness was attributed to further grain refinement, the formation of a larger fraction of high-angle grain boundaries and grain boundaries being closer to equilibrium after recovery.

Grain boundaries and lattice defects in YBa2Cu3O7−x ceramics

1987 ◽  
Vol 5 (11-12) ◽  
pp. 425-428 ◽  
Author(s):  
Wen Shulin ◽  
Feng Jingwei ◽  
Song Xingyun ◽  
Lu Lisheng ◽  
Li Chenghong ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Lattice Defects

Fourier modelling of the anisotropic line broadening of X-ray diffraction profiles due to line and plane lattice defects

1999 ◽  
Vol 32 (4) ◽  
pp. 671-682 ◽  
Author(s):  
Paolo Scardi ◽  
Matteo Leoni
Keyword(s):  
Line Profile ◽  
Lattice Defect ◽  
Structural Parameters ◽  
Lattice Defects ◽  
Line Broadening ◽  
Structural Refinement ◽  
Planar Lattice ◽  
Plane Lattice ◽  
Profile Fitting ◽  
Multi Phase

A new model of line-profile broadening due to the effect of linear and planar lattice defects has been incorporated into the conventional Rietveld algorithm for the structural refinement and whole-pattern fitting of powder data. The proposed procedure, applied to face-centred cubic (f.c.c.) structure materials, permits better modelling, even in the case of anisotropic line broadening and otherhkl-dependent effects that can be related to the presence of dislocations and planar defects (stacking faults and twinning). Besides better quality of the profile fitting, detailed information on the defect structure can be produced: dislocation density and cut-off radius, stacking- and twin-fault probabilities can be refined together with the structural parameters. For each phase (in different samples or in multi-phase samples) the appropriatesize–strainmodel can be selected. The Fourier formalism, which is the basis of the line-profile modelling, also permits an easy adaptation to different lattice-defect models. New approaches can be easily introduced and tested against or together with the existing ones. Finally, the devised program can also be used for the simulation of powder patterns for materials with different types and amounts of line and plane lattice defects.

Using origami design principles to fold reprogrammable mechanical metamaterials

Science ◽  
2014 ◽  
Vol 345 (6197) ◽  
pp. 647-650 ◽  
Author(s):  
Jesse L. Silverberg ◽  
Arthur A. Evans ◽  
Lauren McLeod ◽  
Ryan C. Hayward ◽  
Thomas Hull ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Compressive Modulus ◽  
Unit Cell ◽  
Lattice Defects ◽  
Programmable Matter ◽  
Nanometer Size ◽  
Scale Free ◽  
Mechanical Metamaterials ◽  
Geometric Character ◽  
Crystallographic Structures

Although broadly admired for its aesthetic qualities, the art of origami is now being recognized also as a framework for mechanical metamaterial design. Working with the Miura-ori tessellation, we find that each unit cell of this crease pattern is mechanically bistable, and by switching between states, the compressive modulus of the overall structure can be rationally and reversibly tuned. By virtue of their interactions, these mechanically stable lattice defects also lead to emergent crystallographic structures such as vacancies, dislocations, and grain boundaries. Each of these structures comes from an arrangement of reversible folds, highlighting a connection between mechanical metamaterials and programmable matter. Given origami’s scale-free geometric character, this framework for metamaterial design can be directly transferred to milli-, micro-, and nanometer-size systems.

Lattice Defects Affecting Moisture-Induced Embrittlement of Ni-based L12 Ordered Intermetallics

1996 ◽  
Vol 460 ◽  
Author(s):  
T. Takasugi ◽  
S. Hanada
Keyword(s):  
Heat Treatment ◽  
Tensile Test ◽  
Grain Boundaries ◽  
Tensile Ductility ◽  
Lattice Defects ◽  
The Other ◽  
Treatment Conditions ◽  
Deformation And Heat Treatment ◽  
Test Atmosphere ◽  
Kinetics Of

ABSTRACTMoisture-induced embrittlement of Ll2 alloys (such as Ni3(Si,Ti) and Ni3AI) is observed by tensile test and SEM fractography. A variety of microstructures were prepared by selecting pre-deformation and heat treatment conditions. It is shown that tensile ductility and the associated fractography depend on structure as well as test atmosphere. Well-annealed specimens are susceptible to moisture-induced embrittlement while pre-deformed specimens are resistive to moisture-induced embrittlement. Also, this embrittlement is generally sensitive to the heat treatment scheme preceded by the pre-deformation. Results indicate that the embrittlement occurs when hydrogen is enriched on grain boundaries. On the other hand, the embrittlement can be suppressed when hydrogen is trapped at lattice defects such as dislocations and vacancies. These results are discussed in association with the kinetics of hydrogen in the pre-deformed microstructure.

Observation of {111} Atomic Planes in Silicon and Germanium

1968 ◽  
Vol 26 ◽  
pp. 342-343
Author(s):  
V. A. Phillips ◽  
J. A. Hugo
Keyword(s):  
Image Quality ◽  
Phase Transformations ◽  
Grain Boundaries ◽  
Lattice Defects ◽  
Local Strains ◽  
Size Scale ◽  
Physical Research ◽  
Acceptable Quality ◽  
Silicon And Germanium ◽  
Lattice Resolution

The resolution of features with a size scale of lattice dimensions promises to open up a whole new field of physical research. Studies of lattice defects, local strains, grain boundaries, and mechanisms of phase transformations appear feasible. Resolution of atom rows or even individual atoms may prove possible. The new Philips EM300 microscope incorporates a number of special features which facilitate lattice resolution studies. Using this instrument we have successfully resolved the (111) planes of 3.27 Å spacing in germanium (Fig.l) previously resolved by Parsons and Hoelke, and the (111) planes of 3.14 Å spacing in silicon (Fig.2). The image quality was very good, permitting enlargement at up to 25X directly off the plate of acceptable quality.

Compositional Control of Ceramic Microstructures: An Overview

1985 ◽  
Vol 60 ◽  
Author(s):  
M. P. Harmer ◽  
H. M. Chan ◽  
D. M. Smyth
Keyword(s):  
Growth Inhibition ◽  
Grain Boundaries ◽  
Surface Diffusion ◽  
Grain Growth ◽  
Lattice Defects ◽  
Compositional Variation ◽  
New Developments ◽  
Sintering Additives ◽  
The Subject ◽  
Compositional Control

AbstractA review is given of the controlled use of compositional variation in the sintering of ceramics. The difficulties in determining the mechanisms of operation of sintering additives are outlined and the mechanistic approaches for studying the subject are described. Important remaining issues, new developments and opportunities for developing unique ceramic microstructures through the controlled use of compositional variation are described. Attention is focused on lattice defects and grain growth inhibition, particle pinning, multiple doping, anion effects, anisotropy effects, scavenging, surface diffusion and the formation of wavy grain boundaries.

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