[B._Beckhoff,_et_al.]_Handbook_of_Practical_X-Ray_(b-ok.org).pdf

7135 473 the 220 diffraction peak p ϑ 1 ϑ 2 20 1 e

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strong fiber texture has been found in the bolt region (Fig. 7.135) [473]. The (220) diffraction peak P ( ϑ 1 = ϑ 2 = 20 . 1 , E 220 = 12.62 keV; α = 35 and β = 83 ) has been used for evaluating at the same time the spatial distrib- utions of pole density (texture map) and strain (residual strain map). Dwell time extended over 10 s/pixel to yield a sufficient count statistics in view of the low intensity. At a step width of 120 µ m 2,232 image points had been acquired. A clear inhomogeneity is revealed in the texture (Fig. 7.136a) as well as in the strain maps (Fig. 7.136b). Two almost parallel strips of high pole density run along the axis of the bolt with a slight shift to the right-hand side. They are supposed to form a tube of about one-third of the bolt diameter in the
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668 D. Rammlmair et al. Texture map Map of peak positions Rel. intensity Tension (c) Compression 0 - r - r +r Tension +r Energy (keV) >12.69 12.66 <12.64 (a) (b) d 0 6.10 - 4 4 - 4 100 0 2 mm D d 2 0 - 2 - 6 0 Fig. 7.136. Cross-section of an aluminum rivet. Distribution maps ( a ) of the in- tensity (pole density, texture) and ( b ) of the shift (residual strain) of the 220 peak at pole P ( α = 35 , β = 83 ). ( c ) The lattice strain ∆d/d across the bolt 3-dimensional rivet. The head of the rivet shows a much lower density of this pole. It is worth noting that it forms a butterfly-shaped minimum, which might result from punching the head during production. Along the bolt is a gradient in compressive residual strain to the head. A dish-shaped maximum of compressive strain (dark) is found in the head, which is related to the butterfly-shaped minimum in the (220) texture map. There is an increased compressive residual strain in the interior of the texture tube (dark) and a tensile strain (bright) to the bolt surface. Statistics has been improved by averaging the peak shifts along a section of the shaft. So the radial distribution of residual strain across the bolt is clearly seen in the graph line (Fig. 7.136c). 7.6.4 Microscale Chemical analyses with high spatial resolution are of major interest in geological applications as minerals are often chemically heterogeneous on the
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Methodological Developments and Applications 669 microscopic scale and these compositional variations are of major importance for understanding the formation processes. Most of this microanalytical work is performed by EMPA due to the spatial resolution in the micrometer range, well-established quantification procedures, and the widespread availability of instruments. While this method is well suited for the determination of major elements it is not sensitive enough to detect trace elements at levels below approximately 100 ppm. To fill this gap, micro-XRF instruments using X-rays for excitation for multielement EDXRF analyses may be used and an in- strument has been developed especially for trace element analyses on single mineral grains [428]. The detection limit of such an instrument is about 5–10 times better than with EMPA but the spatial resolution is about 10–100 times lower. A promising application is the U–Th–Pb dating of grains of monazite as described later. For trace element analyses with higher spatial resolution
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  • Spring '14
  • MichaelDudley

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