Neutron Scattering

lization (generation of dislocations), by deformation during materials processing (plastic
deformation, slip and twinning) and as complex superpositions in the course of natural
seismic processes in geological texture development .
6 .1 Types of Preferred Orientation
One frequently occuring special type of texture are the so-called fibre textures . A fibre texture
is typically found in a sample form which is characterized by a main axis (e .g . a cylinder or a
wire) with strong preferred orientation of the crystallites along this fibre axis and a 360°
rotation symmetry around this axis, i.e . no preferred orientation perpendicular to the fibre
axis . For instance, the texture of cold drawn metal wires with fcc structure is a fibre
texture where cubic directions (zone axis) are oriented parallel to the wire axis .
Another texture type are prefened orientations of special planes, e .g . the hexagonal basis
plane of graphite (see Fig . 18 .4), stacked parallel to each other on a surface plane, e .g . a motor
piston, but without any prefened orientation within this plane (graphite as lubricant for better
gliding) .
More general types comprise both the orientation of a plane (hkl) and a zone axis
[uvw] . Such a system of glide deformation texture is represented by (hkl)[uvw] or more
general {hkl} . There is a preferred orientation of a special crystallographic direction
within the (hkl) planes which are oriented parallel to each other . The deformation of a
fcc metal results in a {111} texture, where cubic {111} planes glide along
directions . Geological deformation textures are described by mineral specifrc glide systems .
6 .2 General Ojectives .
The major objectives of texture analysis are différent in materials and earth sciences . While in
material sciences thé major emphasis is on thé development and control of required preferred
orientations under well defmed experimental conditions of materials processing in order to
evaluate specifrc (anisotropic) macroscopic physical properties for special technological
applications, thé problem in geosciences is just thé opposite and much more complex. The
geologist begins with thé end product, thé rock as it occurs in nature, and attempts to
reconstruct thé processes by which thé texture bas been formed. The texture is a fmgerprint of
thé earth's history and, simultaneously, informs on anisotropies of elastic, magnetic and
thermal properties of rocks constituting thé crust and thé upper mande . Anisotropy needs to
be taken into account in thé interprétation of seismic data, development ofgeological models,
and geophysical prospecting .
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