Cyclic Slip Localization and Crack Initiation in Crystalline Materials

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.

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Surface Relief Formation in Relation to the Underlying Dislocation Arrangement

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.258.526 ◽

2016 ◽

Vol 258 ◽

pp. 526-529 ◽

Cited By ~ 1

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.

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Vacancy Migration Barrier Energetics and Pathways in Silica

MRS Proceedings ◽

10.1557/proc-538-317 ◽

1998 ◽

Vol 538 ◽

Author(s):

L. R. Corrales ◽

R.M. Van Ginhoven ◽

J. Song ◽

H. Jónsson

Keyword(s):

Point Defect ◽

Defect Formation ◽

Vacancy Defect ◽

Elastic Band ◽

Simulation Methodology ◽

Defect Migration ◽

Migration Pathway ◽

Empirical Potentials ◽

Band Method ◽

Migration Pathways

AbstractA study of vacancy defect migration pathways and energetics in a-quartz is carried out using an empirical simulation methodology that is coupled with the nudged elastic band method. Results from this study indicate that the migration pathway for migration is between adjacent sites. We anticipate the results will guide modifications to empirical potentials for use in the study of point defect formation of more complex systems.

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Formation of Persistent Slip Band in Fatigued Copper Single Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100054807 ◽

1982 ◽

Vol 40 ◽

pp. 470-471

Author(s):

N. Y. Jin

Keyword(s):

Volume Fraction ◽

Fatigue Cracks ◽

Wall Structure ◽

Matrix Structure ◽

Dislocation Dipole ◽

Slip Bands ◽

Persistent Slip Bands ◽

The Matrix ◽

Hard Shell ◽

Copper Single Crystals

Localised plastic deformation in Persistent Slip Bands(PSBs) is a characteristic feature of fatigue in many materials. The dislocation structure in the PSBs contains regularly spaced dislocation dipole walls occupying a volume fraction of around 10%. The remainder of the specimen, the inactive "matrix", contains dislocation veins at a volume fraction of 50% or more. Walls and veins are both separated by regions in which the dislocation density is lower by some orders of magnitude. Since the PSBs offer favorable sites for the initiation of fatigue cracks, the formation of the PSB wall structure is of great interest. Winter has proposed that PSBs form as the result of a transformation of the matrix structure to a regular wall structure, and that the instability occurs among the broad dipoles near the center of a vein rather than in the hard shell surounding the vein as argued by Kulmann-Wilsdorf.

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Energetics of point defect formation in Ni3Al

Scripta Materialia ◽

10.1016/s1359-6462(01)01194-0 ◽

2002 ◽

Vol 46 (1) ◽

pp. 37-41 ◽

Cited By ~ 26

Author(s):

Hannes Schweiger ◽

Olga Semenova ◽

Walter Wolf ◽

Wolfgang Püschl ◽

Wolfgang Pfeiler ◽

...

Keyword(s):

Point Defect ◽

Defect Formation

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Point defect formation and annihilation in silica glass by heat-treatment: Role of water and stress

Journal of Non-Crystalline Solids ◽

10.1016/j.jnoncrysol.2007.08.039 ◽

2008 ◽

Vol 354 (14) ◽

pp. 1509-1515 ◽

Cited By ~ 9

Author(s):

J.-W. Lee ◽

M. Tomozawa ◽

R.K. MacCrone

Keyword(s):

Heat Treatment ◽

Point Defect ◽

Silica Glass ◽

Defect Formation

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Point defect formation near the epitaxial Ge(001) growth surface and the impact on phosphorus doping activation

Journal of Applied Physics ◽

10.1063/5.0064952 ◽

2021 ◽

Vol 130 (12) ◽

pp. 125702

Author(s):

Anurag Vohra ◽

Geoffrey Pourtois ◽

Roger Loo ◽

Wilfried Vandervorst

Keyword(s):

Point Defect ◽

Defect Formation ◽

Growth Surface ◽

Phosphorus Doping ◽

The Impact

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Point defect-dislocation interactions in copper following pulsed neutron and electron irradiations

Journal of Physics F Metal Physics ◽

10.1088/0305-4608/17/3/006 ◽

1987 ◽

Vol 17 (3) ◽

pp. 577-592 ◽

Cited By ~ 4

Author(s):

D M Parkin ◽

J A Goldstone ◽

H M Simpson ◽

J M Hemsky

Keyword(s):

Point Defect ◽

Dislocation Interactions ◽

Pulsed Neutron

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On the ab initio calculation of vibrational formation entropy of point defect: the case of the silicon vacancy

EPJ Photovoltaics ◽

10.1051/epjpv/2017006 ◽

2017 ◽

Vol 8 ◽

pp. 85505 ◽

Cited By ~ 2

Author(s):

Pia Seeberger ◽

Julien Vidal

Keyword(s):

Point Defect ◽

First Principles ◽

Defect Formation ◽

Finite Size ◽

Direct Calculation ◽

Finite Size Effects ◽

Numerical Errors ◽

Silicon Vacancy ◽

Size Dependent ◽

Very High

Formation entropy of point defects is one of the last crucial elements required to fully describe the temperature dependence of point defect formation. However, while many attempts have been made to compute them for very complicated systems, very few works have been carried out such as to assess the different effects of finite size effects and precision on such quantity. Large discrepancies can be found in the literature for a system as primitive as the silicon vacancy. In this work, we have proposed a systematic study of formation entropy for silicon vacancy in its 3 stable charge states: neutral, +2 and –2 for supercells with size not below 432 atoms. Rationalization of the formation entropy is presented, highlighting importance of finite size error and the difficulty to compute such quantities due to high numerical requirement. It is proposed that the direct calculation of formation entropy of VSi using first principles methods will be plagued by very high computational workload (or large numerical errors) and finite size dependent results.

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