Extrusions and intrusions in fatigued metals. Part 1. State of the art and history†

Man, Jiří; Obrtlík, Karel; Polák, Jaroslav

doi:10.1080/14786430902917616

Cited by 167 publications

(88 citation statements)

References 139 publications

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“…PSBs emerging at the specimen surface cause so-called persistent slip markings (PSMs) forming a pronounced surface relief composed of extrusions and intrusions [97,98], which are preferred locations for crack initiation. Two different approaches were pursued in the literature investigating the influence of PSBs/PSMs on the crack initiation and propagation [99,100]: (i) development of extrusion/intrusion profile in dependence on the number of cycles [101] and (ii) determination of the half-cycle slip activity of PSB. Schwab et al [84] as well as Hollmann [85] performed half-cycle experiments on nickel single crystals at room temperature [81] and low temperatures [85] in order to study the slip activity of PSBs.…”

Section: Ecci and The Slip Activity Of Psbsmentioning

confidence: 99%

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Weidner

Biermann

2015

Philosophical Magazine

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In 1967, Coates discovered the electron channelling contrast of backscattered electrons (BSEs) in scanning electron microscopy, and by this the possibility to investigate arrangements of lattice defects in deformed microstructures of materials. Since that time, a straightforward development of the scanning electron microscopes as well as of the electron channelling contrast technique took place. Nowadays, the performance of scanning electron microscopes is high enough that the resolution of electron channelling contrast imaging (ECCI) micrographs is comparable with conventional bright field transmission electron microscopy (TEM) micrographs. In the first part of the present paper, a historical review on the development of the ECCI technique starting from its discovery more than 45 years ago up to the combination with other advanced methods of scanning electron microscopy like electron backscatter diffraction or high-resolution selected area channelling patterning in the last few years is given. Major important investigations using this technique for the visualization of individual lattice defects like stacking faults (SFs) and dislocations or dislocation arrangements are chronologically summarized. The second part demonstrates that nowadays, ECCI micrographs taken in high-resolution scanning electron microscopes can be called high-resolution ECCI (HR-ECCI). It is shown that the resolution of individual SFs and dislocations in the HR-ECCI micrographs is comparable to that of conventional TEM (about 15 nm defect image width). Furthermore, the paper is demonstrating that HR-ECCI micrographs can be obtained for various types of materials after different mechanical loadings and different grain sizes ranging from large grain size of 500 μm (cast steel) down to less than 2 μm (γ-TiAl).

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Section: Ecci and The Slip Activity Of Psbsmentioning

confidence: 99%

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Weidner

Biermann

2015

Philosophical Magazine

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“…Accordingly, the mean free path of dislocations is kept constant and this value scales with c * . Smaller c * induces a quicker increase of SSD densities and its saturation value is also higher, since the saturation density is inversely proportional to the mean free path as shown in Equation (13). By this mechanism, the first term of the increment of the atomic vacancy density scales with 1/c * .…”

Section: Accumulation and Annihilation Of The Ssds And A Modified Modmentioning

confidence: 93%

“…Vacancy concentration in Fe deformed 20% at room temperature was reported to be at the order of 10 −5 [1], which is obviously far beyond the thermal equilibrium concentration. There have been a wide variety of studies on the effect of excess vacancies on diffusion [2,3], nucleation of precipitate [4], recrystallisation [5], movement of grain boundaries [6,7], creep deformation [8], generation of nano-voids [9][10][11], fatigue crack initiation in persistent slip bands [12][13][14][15] and strain localisation and plastic instability [16][17][18]. Interactions between hydrogen and vacancy [19,20], or hydrogen-vacancy complex and dislocations [21] are other points of current discussion.…”

Section: Introductionmentioning

confidence: 99%

Generation and accumulation of atomic vacancies due to dislocation movement and pair annihilation

Ohashi

2018

Philosophical Magazine

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Generation and accumulation of atomic vacancy due to pair annihilation of edge dislocations during plastic slip deformation of metallic materials are numerically evaluated by crystal plasticity analysis. Dislocation density-based models are utilised in the deformation analysis and a theoretical model for the generation of atomic vacancies is introduced. Purely uniform single-and double-slip deformations are analysed and results show that the evolution of the vacancy density depends largely on the microstructure length scale and multiplication of slip activity on different slip systems. ARTICLE HISTORY

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“…The threshold values of the intrusion depth for the microcrack initiation were 90 and 160 nm in the axial and torsional fatigue tests, respectively. According to the previous study, 28) the extrusion and intrusion are believed to be critical precursors to the initiation of fatigue cracks. Therefore, the microcrack initiation was considered to occur in the unirradiated austenitic stainless steel regard- Grain boundaries before fatigue test Grain boundaries where microcrack initiated due to fatigue test (RT in air, Δε ta = 0.6%, N = 4-6 x 10 3 ) Fig.…”

Section: Microcrack Initiation In Unirradiated Specimenmentioning

confidence: 99%

Fatigue Crack Initiation in Proton-Irradiated Austenitic Stainless Steel

Nogami

Sato

Hasegawa

2011

Journal of Nuclear Science and Technology

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The effect of irradiation on slip band formation and growth and microcrack initiation behavior under low cycle fatigue in SUS316L austenitic stainless steel was investigated using accelerator-based proton irradiation and a low cycle fatigue test at room temperature in air. The mean space of the slip line in proton-irradiated specimens was 25-40% wider than that in unirradiated specimens under the same number of cycles, possibly due to localized deformation by proton irradiation. The microcrack initiation life of the proton-irradiated specimens was approximately 20% of that of the unirradiated specimens. While the microcrack initiation in the unirradiated specimens was observed at the grain boundary, twin boundary, slip band, and triple junction, that in the proton-irradiated specimens was observed only at the twin boundary and slip band, possibly due to irradiation hardening. The step-height of an extrusion near the microcrack was almost the same in the unirradiated and proton-irradiated specimens regardless of the initiation site (100-150 nm). Therefore, the microcrack initiation was considered to occur when the surface morphology change involving the extrusion exceeded the specific threshold value.

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Extrusions and intrusions in fatigued metals. Part 1. State of the art and history†

Cited by 167 publications

References 139 publications

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Generation and accumulation of atomic vacancies due to dislocation movement and pair annihilation

Fatigue Crack Initiation in Proton-Irradiated Austenitic Stainless Steel

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