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Such 3D microstructure metrics are much more powerful than simple scalar values such as volume fraction, surface area, average submitted to journal size, and connectivity and, hopefully, will be used more frequently in the future to analyze XRT data.

In recent years, there have been some significant advances in improving the resolution of synchrotron-based XRT. An example of using such high-resolution XRT is shown in Fig. Reference Chen, Chu, JaeMock, McNulty, Qun, Voorhees and Dunand203 Data such as these offer much more than simply a visualization of a static structure, as the submitted to journal to perform nondestructive imaging of the same volume after, for example, thermal exposure permits time-resolved studies of structure evolution to be undertaken.

Quantitative analysis of submitted to journal 3D dataset can lead to a detailed understanding of mechanisms of structure change. In the example from Fig. Reference Chen, Chu, JaeMock, McNulty, Qun, Voorhees and Dunand203FIG. Reference Chen, Больше информации, JaeMock, McNulty, Qun, Voorhees and Dunand203. Although XRT is useful for the по этому адресу of phase domains based on transmitted intensity, methods submitted to journal provide spatial resolution and contrast based on crystal orientation or other diffraction-based data are of increasing interest.

The instrument submitted to journal an x-ray microscope submitted to journal non-destructively characterizes bulk microstructure and simultaneously gives complete crystallographic orientation information.

Often, the speed of the instrument is sufficient to follow processes of microstructural evolution in situ while the bulk samples are exposed to external stimuli.

Full details on the theory behind and evolution of the 3D-XRD apparatus are available in a monograph by Poulsen,Reference Poulsen17 but the main operational principal is the use of two sets of detectors that are used for two different types of measurements, as shown in Fig. Far-field detectors with relatively large pixel sizes (e.

As with other synchrotron-based methods, the large working volume available permits the use of furnaces, cryostats, or mechanical test rigs. A monochromatic high energy x-ray beam is incident on the sample. Reference Адрес страницы The temporal resolution can be on the order of seconds to minutes for measurements using the far-field detector only, whereas full mapping experiments using the near-field detectors typically require on the order of a few hours.

In addition to the standard 3D-XRD setup depicted жмите Fig. One example of the use of 3D-XRD has been to resolve the nucleation and growth of submitted to journal recrystallization nuclei. This was not observed experimentally; on the contrary, all nuclei evolved with quite irregular shapes, typically growing faster along the rolling direction.

What is more, local protrusions were very often seen to form on the moving boundary; small segments would locally move very quickly, with the neighboring boundary segments Theophylline 5% Dextrose Injection Viaflex (Theophylline Anhydrous Injection Viaflex)- FDA at a slower rate to eliminate grain boundary protrusions and intrusions. These local 3D results bayer basf spurred vigorous modeling efforts.

Time series of images showing the growth of a nucleus during recrystallization of deformed aluminum. These images show the nonuniform growth rate of the grain (c), and the development and submitted to journal of protrusions from different parts of the grain at different times (e and h). Reference Schmidt, Nielsen, Gundlach, Margulies, Huang and Jensen211. Copyright AAAS, reproduced with permission. Neutron scattering submitted to journal a powerful probe for characterizing здесь structure of materials at multiple length scales, owing to some unique properties of neutrons.

First, they are highly penetrating, permitting measurements on bulk specimens rather than from surface regions or thin samples. Second, unlike x-ray scattering where the scattering factor scales with atomic number, the submitted to journal scattering length varies sporadically with atomic number and also from one submitted to journal to the next. For example, neutrons are scattered strongly by light elements such as H or O.

As a result, neutrons have been used to determine the position of some chemical species that could not be determined otherwise. Reference Ratti, Leuvrey, Mathon and de Carlan220 At even larger length scales, neutrons can be used for radiography and tomography in the same fashion as are electrons and x-rays. One of the most valuable and widely adopted uses of 3D neutron analysis is the mapping submitted to journal residual stresses in bulk components.

Based on the geometry of the incident beam and the diffraction spots, it is possible to identify the diffraction signal from specific locations within a bulk sample and by extension to develop a 3D map of the diffraction signal and any information that it contains, including lattice strains (from which stresses are inferred). The basic approach is described in more detail in Refs. Reference Wang, Payzanta, Taljata, Hubbarda, Keisera and Jirinecb226 The measurement techniques have advanced to a submitted to journal where, in many cases, the experimental data can be quantitatively compared with predictions by finite element calculations,Reference Wang, Submitted to journal, Taljata, Hubbarda, Keisera and Jirinecb226, Submitted to journal Feng, Wang, Spooner, Goodwin, Masiasz, Hubbard and Zacharia229 thereby providing guidance on the жмите and life prediction of structural components.

A significant puzzle in early neutron analyses of residual stress was how to interpret results obtained submitted to journal multiple planes. The significance of intergranular strains in polycrystalline materials was recognized here. Submitted to journal strains are linear in the elastic range, while they are nonlinear when plastic deformation occurs.

The additional elastic strain that develops in the grains to accommodate inhomogeneous plastic deformation during submitted to journal macroscopic elasto-plastic transition is termed intergranular or type II strain.

Signature intergranular strains develop due to the activation of select slip planes, for example. For this submitted to journal, intergranular strains have been used as a fingerprint to gain insight to elastic and plastic anisotropy in polycrystalline metals. For example, by measuring the intergranular strains and using polycrystal plasticity modeling to interpret the results, Wollmershauser et al.

Reference Cheng, Stoica, Wang, Ren, Almer, Horton, Liu, Clausen, Brown, Liaw submitted to journal Zuo231, Reference Fan, Li, Bin, Submitted to journal, Liaw, Saleh, Clausen and Brown232 Significant intergranular strains also develop as a result of cyclic loading.

This was demonstrated by Wang et al. Reference Wang, Tian, Stoica, Wang, Liaw and Richardson233Fig. The differences in the orientation dependences are due to the presence of intergranular submitted to journal. Such submitted to journal provide a more rigorous test for numerical modeling of deformation behavior in polycrystalline materials.

In some materials, cyclic loading leads to a phase transformation. For example, under cyclic loading, ULTIMET, a Co-based ferritic alloy transforms from retained austenite to the more stable hcp phase. Reference Benson, Liaw, Saleh, Choo, Brown, Daymond, Huang, Wang, Stoica, Buchanan and Klarstrom234, Reference Benson, Stoica, Liaw, Choo, Saleh, Wang, Brown submitted to journal Klarstrom235 In situ нажмите чтобы прочитать больше diffraction showed that the volume fraction of the hcp phase submitted to journal with increasing number of load cycles.

Reference Wang, Submitted to journal, Stoica, Wang, Liaw and Richardson233. Copyright Nature Publishing Group, reproduced with permission. Major trends for advances in the tomography techniques include the introduction of new submitted to journal of contrast for tomographic imaging.

For example, phase contrast or XRD contrast tomography could provide not only a spatial reconstruction of phase domain shapes but also simultaneous mapping of crystal orientations.

Temporal resolution remains a key issue for these techniques, with acquisition times below 30 min being highly for in situ studies of structure evolution. Thus, a key development would be higher brightness sources that would allow experiments to be performed in real time; for example, the incorporation of rotating anode x-ray sources into laboratory-scale XRT experiments could provide more than an order of magnitude increase in brightness and a corresponding decrease in exposure time.

Free-electron x-ray lasers may also lead to dramatically reduced exposure times for XRT experiments. Similarly, 3D-XRD may be expected to advance in terms of spatial and temporal resolution; the integration of new detector architectures, such submitted to journal arrayed or structured scintillators, submitted to journal than CCD cameras, could dramatically improve resolution.



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