Effect of Grain Boundaries and Grain Orientation on Structure and Properties

Hansen, Niels; Huang, Xiaoxu; Winther, Grethe

doi:10.1007/s11661-010-0292-5

Cited by 47 publications

(25 citation statements)

References 55 publications

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“…We can incorporate this in an approximate way by making the proportionality factor in Eq. (35) inversely proportional to the GND density. We measure the latter by summing the square of all components of , hence | | = ijk ijk /2 and v u = D | | σ mk umk , where D is a positive material-dependent constant.…”

Section: Climb-glide Dynamics (Cgd)mentioning

confidence: 99%

Scaling theory of continuum dislocation dynamics in three dimensions: Self-organized fractal pattern formation

Chen

Choi

Papanikolaou

et al. 2013

International Journal of Plasticity

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We focus on mesoscopic dislocation patterning via a continuum dislocation dynamics theory (CDD) in three dimensions (3D). We study three distinct physically motivated dynamics which consistently lead to fractal formation in 3D with rather similar morphologies, and therefore we suggest that this is a general feature of the 3D collective behavior of geometrically necessary dislocation (GND) ensembles. The striking self-similar features are measured in terms of correlation functions of physical observables, such as the GND density, the plastic distortion, and the crystalline orientation. Remarkably, all these correlation functions exhibit spatial power-law behaviors, sharing a single underlying universal critical exponent for each type of dynamics. PACS numbers: 61.72.Bb, 61.72.Lk, 05.45.Df, 05.45.Pq I. INTRODUCTIONDislocations in plastically deformed crystals, driven by their long-range interactions, collectively evolve into complex heterogeneous structures where dislocation-rich cell walls or boundaries surround dislocation-depleted cell interiors. These have been observed both in single crystals 1-3 and polycrystals 4 using transmission electron microscopy (TEM). The mesoscopic cellular structures have been recognized as scale-free patterns through fractal analysis of TEM micrographs 5-8 . The complex collective behavior of dislocations has been a challenge for understanding the underlying physical mechanisms responsible for the development of emergent dislocation morphologies.Complex dislocation microstructures, as an emergent mesoscale phenomenon, have been previously modeled using various theoretical and numerical approaches 9 . Discrete dislocation dynamics (DDD) models have provided insights into the dislocation pattern formations: parallel edge dislocations in a two-dimensional system evolve into 'matrix structures' during single slip 10 , and 'fractal and cell structures' during multiple slip 11,12 ; random dislocations in a threedimensional system self-organize themselves into microstructures through junction formation, cross-slip, and shortrange interactions 13,14 . However, DDD simulations are limited by the computational challenges on the relevant scales of length and strain. Beyond these micro-scale descriptions, CDD has also been used to study complex dislocation structures. Simplified reaction-diffusion models have described persistent slip bands 15 , dislocation cellular structures during multiple slip 16 , and dislocation vein structures 17 . Stochasticity in CDD models 7,10,18 or in the splittings and rotations of the macroscopic cells 19-21 have been suggested as an explanation for the formation of organized dislocation structures. The source of the noise in these stochastic theories is derived from either extrinsic disorder or short-length-scale fluctuations.In a recent manuscript 22 , we analyzed the behavior of a grossly simplified continuum dislocation model for plasticity 22-26 -a physicist's 'spherical cow' approximation designed to explore the minimal ingredients necessary to explain key ...

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Section: Climb-glide Dynamics (Cgd)mentioning

confidence: 99%

Scaling theory of continuum dislocation dynamics in three dimensions: Self-organized fractal pattern formation

Chen

Choi

Papanikolaou

et al. 2013

International Journal of Plasticity

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“…However, such studies have been conducted for pure polycrystalline copper, aluminum, and nickel (i.e., with higher SFE than 304 and 316 steels) through tensile tests at room temperature (e.g., [85,86]). They revealed (see brief synthesis in [87]) strong differences of dislocation patterns according to grain orientation with respect to the tensile axis, as shown in Fig. 8.…”

Section: >mentioning

confidence: 84%

“…8. Furthermore, extensive TEM, Scanning Electron Microscopy (SEM) and Electron Backscattering Diffraction (EBSD) studies (e.g., [12,87,88] Even though the strain contribution from twinning is small, it is well admitted that twinning contributes to the impressive elongations of several alloys (e.g., TWIP steels). This is attributed to the hardening produced by twins acting as strong obstacles to dislocation gliding.…”

Section: >mentioning

confidence: 99%

Tailoring plasticity of austenitic stainless steels for nuclear applications: Review of mechanisms controlling plasticity of austenitic steels below 400 °C

Bellefon

Duysen

2016

Journal of Nuclear Materials

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AISI 304 and 316 austenitic stainless steels were invented in the early 1900s and are still trusted by materials and mechanical engineers in numerous sectors because of their good combination of strength, ductility, and corrosion resistance, and thanks to decades of experience and data. This article is part of an effort focusing on tailoring the plasticity of both types of steels to nuclear applications. It provides a synthetic and comprehensive review of the plasticity mechanisms in austenitic steels during tensile tests below 400°C. In particular, formation of twins, extended stacking faults, and martensite, as well as irradiation effects and grain rotation are discussed in details.

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“…However, a sharp increase occurs from three-millimeter to four-millimeter depth and the hardness continuously increases from 384 Hv to 572 Hv. According to the microstructure evaluation discussed above, during FSW process, an austenitic transformation occurred in SZ and the degree is verified on the basis of thermal distribution due to inhomogeneous cooling or heat flux within the weld [47]. Given the SZ-bottom with a higher cooling rate, a lower peak temperature was obtained and therefore a lower proportion of martensitic underwent phase transformation, resulting in a higher hardness relative to that of the SZ-top.…”

Section: Micro-hardness Distributionmentioning

confidence: 99%

Microstructure, Mechanical and Corrosion Properties of Friction Stir Welding High Nitrogen Martensitic Stainless Steel 30Cr15Mo1N

Geng

Feng

et al. 2016

Metals

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High nitrogen martensitic stainless steel 30Cr15Mo1N plates were successfully welded by friction stir welding (FSW) at a tool rotation speed of 300 rpm with a welding speed of 100 mm/min, using W-Re tool. The sound joint with no significant nitrogen loss was successfully produced. Microstructure, mechanical and corrosion properties of an FSW joint were investigated. The results suggest that the grain size of the stir zone (SZ) is larger than the base metal (BM) and is much larger the case in SZ-top. Some carbides and nitrides rich in chromium were found in BM while not observed in SZ. The martensitic phase in SZ could transform to austenite phase during the FSW process and the higher peak temperature, the greater degree of transformation. The hardness of SZ is significantly lower than that of the BM. An abrupt change of hardness defined as hard zone (HZ) was found in the thermo-mechanically affected zone (TMAZ) on the advancing side (AS), and the HZ is attributed to a combination result of temperature, deformation, and material flow behavior. The corrosion resistance of SZ is superior to that of BM, which can be attributed to less precipitation and lower angle boundaries (LABs). The corrosion resistance of SZ-bottom is slight higher than that of SZ-top because of the finer grained structure.

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Effect of Grain Boundaries and Grain Orientation on Structure and Properties

Cited by 47 publications

References 55 publications

Scaling theory of continuum dislocation dynamics in three dimensions: Self-organized fractal pattern formation

Scaling theory of continuum dislocation dynamics in three dimensions: Self-organized fractal pattern formation

Tailoring plasticity of austenitic stainless steels for nuclear applications: Review of mechanisms controlling plasticity of austenitic steels below 400 °C

Microstructure, Mechanical and Corrosion Properties of Friction Stir Welding High Nitrogen Martensitic Stainless Steel 30Cr15Mo1N

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