Surface Relief Formation in Relation to the Underlying Dislocation Arrangement

2016 ◽  
Vol 258 ◽  
pp. 526-529 ◽  
Author(s):  
Veronika Mazánová ◽  
Milan Heczko ◽  
Ivo Kuběna ◽  
Jaroslav Polák
Keyword(s):  
Electron Microscopy ◽  
Dislocation Structure ◽  
Fatigue Crack Initiation ◽  
Surface Profile ◽  
Specimen Surface ◽  
Slip Bands ◽  
Transmission Electron ◽  
Persistent Slip Bands ◽  
Relief Formation ◽  
Cyclic Slip

Two fatigued materials with f.c.c. lattice, i.e. pure polycrystalline copper and austenitic Sanicro 25 stainless steel, were subjected to the study of the persistent slip markings (PSMs) developed on the surface of the suitably oriented grains. They were observed using scanning electron microscopy (SEM) and thin surface FIB lamellae were prepared and studied by transmission electron microscopy (TEM). The aim was to correlate the specimen surface profile with the underlying internal dislocation structure. The localization of the intensive cyclic slip into persistent slip bands (PSBs) of the material was observed and associated with the PSMs on the specimen surface. Extrusions, intrusions and the dislocation structure appertaining to them were analysed, documented and discussed in relation to the models of fatigue crack initiation.

Plasticity and Microstructure of Irradiated Pd

1998 ◽  
Vol 540 ◽  
Author(s):  
N. Baluc ◽  
Y. Dai ◽  
M. Victoria
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plastic Deformation ◽  
Ambient Temperature ◽  
Tensile Deformation ◽  
Microscopic Level ◽  
Macroscopic Scale ◽  
Slip Bands ◽  
Transmission Electron ◽  
Mev Protons

AbstractSingle crystalline specimens of pure Pd have been irradiated at ambient temperature with 590 MeV protons to doses ranging between 10−4 and 10−1 dpa. Tensile deformation experiments revealed that irradiation induces hardening and embrittlement, while scanning (SEM) and transmission electron microscopy (TEM) observations showed that plastic deformation of specimens irradiated to a dose ≥ 10−2 dpa is strongly localized and yields the creation of slip bands at the macroscopic scale and of defect-free channels at the microscopic level.

Substructures in deformed Fe-15 Ni-0.8 C austenite

1984 ◽  
Vol 42 ◽  
pp. 472-473
Author(s):  
Anil K. Sachdev ◽  
M. M. Shea
Keyword(s):  
Electron Microscopy ◽  
Shear Bands ◽  
Strain Rates ◽  
Normal Strain ◽  
Austenite Matrix ◽  
Band Formation ◽  
Slip Bands ◽  
Transmission Electron ◽  
The Common ◽  
Intense Shear

In a recent study, the mechanical behavior of an Fe-15 Ni-0.8 C austenite was determined at various strain rates and temperatures. An important finding of this study was the formation of intense shear bands during deformation at temperatures much greater than which bore no resemblance to the common morphologies of martensites. There is much disagreement in the literature regarding the mechanism of band formation and the associated substructure. These bands have been reported to be fine BCC martensite particles or laths delineating slip bands or thin twins in the austenite matrix. The purpose of the present work was to determine by transmission electron microscopy and diffraction the substructure of the fine bands and to attempt to clarify the various interpretations. For comparison, the substructure produced at a lower deformation temperature was also evaluated where the martensite was known to have the normal strain-induced morphology.

Dislocation Dissociation in the Σ13 Grain Boundary in Silicon

1991 ◽  
Vol 238 ◽  
Author(s):  
Laurent Sagalowicz ◽  
Richard Beanland ◽  
William A. T. Clark
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Crystal Lattice ◽  
Dislocation Structure ◽  
Alternative Structures ◽  
Transmission Electron ◽  
Dislocation Dissociation

ABSTRACTTransmission electron microscopy has been used to study the atomic and dislocation structure of deformed and undeformed Σ13 {510} boundary in Si. It is shown that there are several alternative structures for this boundary, which may be separated by imperfect and partial grain boundary dislocations. It is also shown that the dissociation of crystal lattice dislocations which interact with the boundary during deformation results is far more complicated than simple geometrical models applicable in monatomic materials predicts.

The Structure of a Near Coincidence Σ=5, [001] Twist Boundary in Silicon

1982 ◽  
Vol 14 ◽  
Author(s):  
Mark Vaudin ◽  
Dieter Ast
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Dislocation Structure ◽  
Lattice Theory ◽  
Small Deviation ◽  
Twist Boundary ◽  
Transmission Electron ◽  
Primary Dislocation ◽  
Dislocation Content

ABSTRACTThe dislocation structure of a near coincidence Σ=5 [001]twist boundary in silicon was studied using transmission electron microscopy. Secondary dislocations, with localized cores, were observed in the boundary accommodating a small deviation (<.5°) from perfect coincidence. The O-lattice theory for general low angle boundaries was extended to calculate the expected dislocation content of near coincidence boundaries. Comparison between predictions and observations was used to deduce information on the primary dislocation structure of the boundary.

Cyclic Slip Localization and Crack Initiation in Crystalline Materials

2014 ◽  
Vol 891-892 ◽  
pp. 452-457 ◽  
Author(s):  
Jaroslav Polák ◽  
Jiří Man
Keyword(s):  
Point Defect ◽  
Defect Formation ◽  
Fatigue Cracks ◽  
Extended Model ◽  
Crystalline Materials ◽  
Defect Migration ◽  
Persistent Slip Bands ◽  
Dislocation Interactions ◽  
Relief Formation ◽  
Cyclic Slip

Cyclic plastic straining in crystalline materials is localized to persistent slip bands (PSBs) and results in formation of persistent slip markings (PSMs) consisting of extrusions and intrusions. Intensive plastic strain in PSBs results in dislocation interactions and formation of point defects. The extended model based on point defect formation, migration and annihilation is presented describing surface relief formation in the form of extrusion-intrusion pairs. Point defect migration and resulting mass transfer is the principle source of cyclic slip irreversibility leading to crack-like defects - intrusions. Fatigue cracks start in the tip of sharp intrusions.

Sign in / Sign up

Export Citation Format

Share Document