Orientation of grains

Material factors. The main metallurgical properties of importance are alloy composition, distribution of alloying elements and impurities, microstructure and crystal structure, heat treatment, mechanical working, preferred orientation of grains and grain boundaries (texture), mechanical properties (strength, fracture toughness, etc.).31... 

Material parameters in SCC. The susceptibility to SCC is affected by the chemical composition, the preferential orientation of grains, the composition and the distribution of the precipitates (particularly intergranular), the interaction of dislocations, the progression of the phase transformations and cold work.16... 

The crystalline deposits show remarkable brightness resulting from a preferred orientation of grains. Surface structures of crystalline deposits are significantly different from those of amorphous deposits. The microstructure characteristics of the crystalline deposits are strongly dependent on the deposition conditions, as shown in Figure 6.12a-c. 

We described in detail the method for illustrating a non-random orientation of grains in a film. We are now going to continue by describing the methods for quantifying this orientation. 

This is the most widely used method for the determination of the phase composition of powders. The x-ray diffractometer contains a source of monochromatic x-rays that irradiate the sample and are diffracted from atomic planes and detected. The angle of diffraction of x-rays by the crystalline planes is characteristic of the crystal structure, and the intensity of scattered radiation is characteristic of the atomic composition. In recent years, automated data processing has enabled higher accuracy and speed. A number of problems are encountered in the quantitative determination of phases in fine powders. Some of these are overlap of phase peaks (e.g., in silicon nitride), orientation of grains, and presence of coarse particles. The last produces distortion of the diffraction data. A number of standard reference materials for XRPD have been developed for use in improving the quality of data [37]. 

Magnetic properties can also be strongly modified by a preferential orientation of grains (in many texts, it is known simply as texture). 

Soft ferromagnetic materials for ac applications are usually prepared in the form of thin laminated sheets (essentially to decrease eddy-current losses see the end of this section). A proper combination of rolling and annealing processes can lead to a preferential orientation of grains, which results in extremely favourable magnetic properties. The fabrication steps for electrical steels are listed in Table 6.3. 

Most corrosion costs are due to corrosion in electrolytes, or wet corrosion. Local differences in a given metal can be chemical or mechanical in nature, for example, impurities such as oxides and other inclusions, grain boundaries, orientation of grains, differences in composition of the microstructure, localized stresses, and scratches and nicks. Highly polished surfaces are used in special cases. Pure and smooth zinc will only corrode slowly in pure hydrochloric add, but pure metals are not often used because they are expensive and have relatively low strength. 

In many respects amorphous alloys can be regarded as having isotropic properties. Texture or preferred orientation of grains as encountered in crystalline melts are... 

When studying amorphous materials and incompletely ordered particles in polycrystals, X-ray diffraction analysis is used to determine the phase composition, size, and orientation of grains (texture). 

The crystallography of GB can be minimally specified by five variables three parameters to specify the relative orientation of one grain with respect to the other, and two parameters to indicate the grain boundary inclination [3]. (Note the distinct orientations of grains indicated in Fig. lb a misorientation angle describes a rotation of one grain that will cause it to coincide in orientation with the other). While these variables characterize the basic GB crystallography, they do not fully specify GB atomic structure. This has been variously described in terms of... 

Recently, we reported the ordering kinetics between HEX and BCC microdomains for polystyrene-Wock-polyisoprene-6/ocifc polys ene (SIS) copolymer (13). In ref (13), we employed an as-cast sample that was not aligned in a macroscopic scale. In this situation a small angle X-ray scatto-ing with one-dimensional detector (1-D SAXS) could be employed to study the ordering kinetics because of the random orientations of grains in the block copolymer. Also, in a separate paper we have shown that during the transition... 

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