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- 2016 (3) (entfernen)
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- Zeitschriftenartikel (3) (entfernen)
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- Englisch (3)
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- Electron backscatter diffraction (3) (entfernen)
The thermal stability of the microstructure of a heat-resistant cobalt alloy, which consists of a γ solid solution strengthened with γ'-phase precipitates, has been studied. The temperature behavior of the dissolution of the hardening γ' phase and the kinetics of its coarsening at 700 and 800°C have been determined. It is found that, during prolonged annealing at 800°C, the γ' → β phase transformation occurs.
A typical electron backscatter diffraction (EBSD) pattern usually contains more than a hundred of Kikuchi poles that formed by intersecting dozens of visible Kikuchi bands. The poles correspond to zone axes in real space or lattice planes in reciprocal space. The band widths are inversely proportional to the interplanar spacings of diffracting lattice planes, and the angle formed by the beam source and two band center-lines approximately corresponds to angle between two lattice planes. However, EBSD patterns always suffer from gnomic distortions. In addition, the band width measurement has a relative error of 5-20% due to the complex profile. Thus, an EBSD pattern always provides abundant crystallographic information but disappointingly low accuracy.
The inverse pole figure (IPF) coloring for a suitable evaluation of crystal
orientation data is discussed. The major goal is a high correlation between
encoding color and crystal orientation. Revised color distributions of the
fundamental sectors are introduced which have the advantages of (1) being
applicable for all point groups, (2) not causing color discontinuities within grains,
(3) featuring carefully balanced regions for red, cyan, blue, magenta, green and
yellow, and (4) an enlarged gray center in opposition to a tiny white center. A
new set of IPF color keys is proposed which is the result of a thorough analysis
of the colorization problem. The discussion considers several topics: (a) the
majority of presently applied IPF color keys generate color discontinuities for
specifically oriented grains; (b) if a unique correlation between crystal direction
and color is requested, discontinuity-preventing keys are possible for all point
groups, except for 4, 3 and 1; (c) for a specific symmetry group several IPF color
keys are available, visualizing different features of a microstructure; and (d) for
higher symmetries a simultaneous IPF mapping of two or three standard
reference directions is insufficient for an unequivocal orientation assignment.
All color keys are available in MTEX, a freely available MATLAB toolbox.