Neutron Scattering

4.0 Experimental Texture Analysis
The material texture and its ODF cannot be measured directly without destroying the
specimen . The ODF can only be constructed . Two différent types of measurements are
applied . The traditional method is thé single grain analysis based on optical methods where
thé orientations of representative single grains are directly observed using universal stage
microscopy on a polished sample surface . A faster and much more efficient alternative to thé
rather painstaking single grain analysis are diffraction methods using either neutrons or X-
rays . Bragg scattering intensities are measured as a fonction of thé sample orientation .
4.1 Definition of a Pole Figure
A pole figure represents thé orientation distribution of a parfcular crystal direction [hkl] or
thé normal to thé scattering plane (hkl) of thé sample . The crystal direction is first projected
onto a sphere of unit radius around thé sample . The prenetrating point P on thé sphere (Fig .
18 .11) is defmed by two angles, a pole distance a and an azimuth ß . This sphere is then
projected onto a plane in order to represent thé pole on paper . Various spherical projections
are in use, thé most common in texture analysis is thé stereographic projection (sec Fig .
18 .11) . Fig . 18 .12 shows examples of some crystal plane distributions and their associated
pole figure representation .
N
S
Fig. 18 .11 : Representation ofa plane (hkl) by its normal and its pole on thé surrounding
sphere P defined by polar coordiantes a, /3 (left) . Stereographic projection ofP into P *
inside thé (hatched) équatorial plane (right)
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