J. Appl. Cryst.の発刊に際して

Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

X-Ray Diffraction

http://nanomechanics.mit.edu/sites/default/files/documents/Kumar_03.pdf

Mechanical behavior of nanocrystalline metals and alloys

Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling: Theory, experiments, applications

A review of dynamic recrystallization phenomena in metallic materials

Texture evolution governs many of the physical, chemical, and mechanical properties of polycrystalline materials, but texture models have only been tested on the macroscopic level, which makes it hard to distinguish between approaches that are conceptually very different. Here, we present a universal method for providing data on the underlying structural dynamics at the grain and subgrain level. The method is based on diffraction with focused hard x-rays. First results relate to the tensile deformation of pure aluminum. Experimental grain rotations are inconsistent with the classical Taylor and Sachs models.

https://science.sciencemag.org/content/sci/291/5512/2392.full.pdf

In situ measurement of grain rotation during deformation of polycrystals.

A fast and non-destructive method for generating three-dimensional maps of the grain boundaries in undeformed polycrystals is presented. The method relies on tracking of micro-focused high-energy X-rays. It is verified by comparing an electron microscopy map of the orientations on the 2.5 × 2.5 mm surface of an aluminium polycrystal with tracking data produced at the 3DXRD microscope at the European Synchrotron Radiation Facility. The average difference in grain boundary position between the two techniques is 26 µm, comparable with the spatial resolution of the 3DXRD microscope. As another extension of the tracking concept, algorithms for determining the stress state of the individual grains are derived. As a case study, 3DXRD results are presented for the tensile deformation of a copper specimen. The strain tensor for one embedded grain is determined as a function of load. The accuracy on the strain is Δ∊ ≃ 10−4.

Three-dimensional maps of grain boundaries and the stress state of individual grains in polycrystals and powders

The mechanical properties of polycrystalline materials are largely determined by the kinetics of the phase transformations during the production process. Progress in x-ray diffraction instrumentation at synchrotron sources has created an opportunity to study the transformation kinetics at the level of individual grains. Our measurements show that the activation energy for grain nucleation is at least two orders of magnitude smaller than that predicted by thermodynamic models. The observed growth curves of the newly formed grains confirm the parabolic growth model but also show three fundamentally different types of growth. Insight into the grain nucleation and growth mechanisms during phase transformations contributes to the development of materials with optimal mechanical properties.

https://science.sciencemag.org/content/sci/298/5595/1003.full.pdf

Grain nucleation and growth during phase transformations.

We observed the in situ growth of a grain during recrystallization in the bulk of a deformed sample. We used the three-dimensional x-ray diffraction microscope located at the European Synchrotron Radiation Facility in Grenoble, France. The results showed a very heterogeneous growth pattern, contradicting the classical assumption of smooth and spherical growth of new grains during recrystallization. This type of in situ bulk measurement opens up the possibility of obtaining experimental data on scientific topics that before could only be analyzed theoretically on the basis of the statistical characterization of microstructures. For recrystallization, the in situ method includes direct measurements of nucleation and boundary migration through a deformed matrix.

https://science.sciencemag.org/content/sci/305/5681/229.full.pdf

L. Margulies

Papers

In situ measurement of grain rotation during deformation of polycrystals.

Three-dimensional maps of grain boundaries and the stress state of individual grains in polycrystals and powders

Grain nucleation and growth during phase transformations.

Watching the Growth of Bulk Grains During Recrystallization of Deformed Metals

Lattice rotations of individual bulk grains Part II: correlation with initial orientation and model comparison