In
physical chemistry
Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mecha ...
and
materials science, texture is the distribution of crystallographic orientations of a
polycrystalline
A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains.
Bacillite is a type of crystallite. It is rodlike with parallel longulites.
Stru ...
sample (it is also part of the geological
fabric
Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
). A sample in which these orientations are fully random is said to have no distinct texture. If the crystallographic orientations are not random, but have some preferred orientation, then the sample has a weak, moderate or strong texture. The degree is dependent on the percentage of crystals having the preferred orientation.
Texture is seen in almost all engineered materials, and can have a great influence on materials properties. The texture forms in materials during thermo-mechanical processes, for example during production processes e.g.
rolling
Rolling is a type of motion that combines rotation (commonly, of an axially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exist, the two are in contact ...
. Consequently, the rolling process is often followed by a heat treatment to reduce the amount of unwanted texture. Controlling the production process in combination with the characterization of texture and the material's microstructure help to determine the materials properties, i.e. the ''processing-microstructure-texture-property relationship''. Also,
geologic
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...
rocks show texture due to their thermo-mechanic history of formation processes.
One extreme case is a complete lack of texture: a solid with perfectly random crystallite orientation will have
isotropic
Isotropy is uniformity in all orientations; it is derived . Precise definitions depend on the subject area. Exceptions, or inequalities, are frequently indicated by the prefix ' or ', hence ''anisotropy''. ''Anisotropy'' is also used to describe ...
properties at length scales sufficiently larger than the size of the crystallites. The opposite extreme is a perfect single crystal, which likely has
anisotropic
Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...
properties by geometric necessity.
Characterization and representation
Texture can be determined by various methods.
Some methods allow a quantitative analysis of the texture, while others are only qualitative. Among the quantitative techniques, the most widely used is
X-ray diffraction
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
using texture goniometers, followed by the
electron backscatter diffraction (EBSD) method in
scanning electron microscopes. Qualitative analysis can be done by
Laue photography, simple X-ray diffraction or with a
polarized microscope.
Neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
and synchrotron
high-energy X-ray diffraction are suitable for determining textures of bulk materials and
in situ
''In situ'' (; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in ...
analysis, whereas laboratory x-ray diffraction instruments are more appropriate for analyzing textures of thin films.
Texture is often represented using a
pole figure
A pole figure is a graphical representation of the orientation of objects in space. For example, pole figures in the form of stereographic projections are used to represent the orientation distribution of crystallographic lattice plane (mathematics ...
, in which a specified
crystallographic
Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The word ...
axis (or pole) from each of a representative number of crystallites is plotted in a stereographic projection, along with directions relevant to the material's processing history. These directions define the so-called sample reference frame and are, because the investigation of textures started from the cold working of metals, usually referred to as the rolling direction ''RD'', the transverse direction ''TD'' and the normal direction ''ND''. For drawn metal wires the cylindrical fiber axis turned out as the sample direction around which preferred orientation is typically observed (see below).
File:Diffractometre berceau Euler.png, Four circles diffractometer, or Eulerian cradle, for texture measurement with X-ray diffraction
File:Diffractometre montage chi reflexion.png, χ mode for reflection measurement
File:Diffractometre montage omega transmission.png, Ω mode for transmission measurement
Common textures
There are several textures that are commonly found in processed (cubic) materials. They are named either by the scientist that discovered them, or by the material they are most found in. These are given in
Miller indices
Miller indices form a notation system in crystallography for lattice planes in crystal (Bravais) lattices.
In particular, a family of lattice planes of a given (direct) Bravais lattice is determined by three integers ''h'', ''k'', and '' ...
for simplification purposes.
*Cube component: (001)
00*Brass component: (110)
112 112 may refer to:
*112 (number), the natural number following 111 and preceding 113
*112 (band), an American R&B quartet from Atlanta, Georgia
**112 (album), ''112'' (album), album from the band of the same name
*112 (emergency telephone number), t ...
*Copper component: (112)
1-1*S component: (123)
3-4
Orientation distribution function
The full 3D representation of crystallographic texture is given by the orientation distribution function (
) which can be achieved through evaluation of a set of pole figures or diffraction patterns. Subsequently, all pole figures can be derived from the
.
The
is defined as the volume fraction of grains with a certain orientation
.
:
The orientation
is normally identified using three
Euler angles
The Euler angles are three angles introduced by Leonhard Euler to describe the Orientation (geometry), orientation of a rigid body with respect to a fixed coordinate system.Novi Commentarii academiae scientiarum Petropolitanae 20, 1776, pp. 189 ...
. The Euler angles then describe the transition from the sample’s reference frame into the crystallographic reference frame of each individual grain of the polycrystal. One thus ends up with a large set of different Euler angles, the distribution of which is described by the
.
The orientation distribution function,
, cannot be measured directly by any technique. Traditionally both X-ray diffraction and EBSD may collect pole figures. Different methodologies exist to obtain the
from the pole figures or data in general. They can be classified based on how they represent the
. Some represent the
as a function, sum of functions or expand it in a series of harmonic functions. Others, known as discrete methods, divide the
space in cells and focus on determining the value of the
in each cell.
Origins
In
wire
Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm
A wire is a flexible strand of metal.
Wire is c ...
and
fiber
Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...
, all crystals tend to have nearly identical orientation in the axial direction, but nearly random radial orientation. The most familiar exceptions to this rule are
fiberglass
Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth ...
, which has
no crystal structure, and
carbon fiber
Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...
, in which the crystalline anisotropy is so great that a good-quality filament will be a distorted single crystal with approximately cylindrical symmetry (often compared to a
jelly roll). Single-crystal fibers are also not uncommon.
The making of
metal sheet often involves compression in one direction and, in efficient rolling operations, tension in another, which can orient crystallites in both axes by a process known as
grain flow. However,
cold work
Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00K on the Kelvin scale, an absolute thermodynamic ...
destroys much of the crystalline order, and the new crystallites that arise with
annealing usually have a different texture. Control of texture is extremely important in the making of
silicon steel
Electrical steel (E-steel, lamination steel, silicon electrical steel, silicon steel, relay steel, transformer steel) is an iron alloy tailored to produce specific magnetic properties: small hysteresis area resulting in low power loss per cycle ...
sheet for
transformer
A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
cores (to reduce
magnetic
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particle ...
hysteresis
Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of ...
) and of
aluminium can
An Aluminum can (British English: Tin can) is a single-use container for packaging made primarily of aluminum.
It is commonly used for food and beverages such as milk and soup but also for products such as oil, chemicals, and other liquids. Globa ...
s (since
deep drawing
Deep drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch. It is thus a shape transformation process with material retention. The process is considered "dee ...
requires extreme and relatively uniform
plasticity
Plasticity may refer to:
Science
* Plasticity (physics), in engineering and physics, the propensity of a solid material to undergo permanent deformation under load
* Neuroplasticity, in neuroscience, how entire brain structures, and the brain it ...
).
Texture in
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
s usually arises because the crystallites in a
slurry
A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pu ...
have shapes that depend on crystalline orientation, often needle- or plate-shaped. These particles align themselves as water leaves the slurry, or as clay is formed.
Casting
Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a ''casting'', which is ejected ...
or other fluid-to-solid transitions (i.e.,
thin-film deposition
A thin film is a layer of material ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many a ...
) produce textured solids when there is enough time and activation energy for atoms to find places in existing crystals, rather than condensing as an
amorphous solid
In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal.
Etymology
The term comes from the Greek ''a'' ("wit ...
or starting new crystals of random orientation. Some
facet
Facets () are flat faces on geometric shapes. The organization of naturally occurring facets was key to early developments in crystallography, since they reflect the underlying symmetry of the crystal structure. Gemstones commonly have facets cut ...
s of a crystal (often the close-packed planes) grow more rapidly than others, and the crystallites for which one of these planes faces in the direction of growth will usually out-compete crystals in other orientations. In the extreme, only one crystal will survive after a certain length: this is exploited in the
Czochralski process (unless a
seed crystal is used) and in the casting of
turbine
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...
blades and other
creep-sensitive parts.
Texture and materials properties
Material properties such as
strength
Strength may refer to:
Physical strength
*Physical strength, as in people or animals
* Hysterical strength, extreme strength occurring when people are in life-and-death situations
*Superhuman strength, great physical strength far above human c ...
,
chemical reactivity,
stress corrosion cracking
Stress corrosion cracking (SCC) is the growth of crack formation in a corrosive environment. It can lead to unexpected and sudden failure of normally ductile metal alloys subjected to a tensile stress, especially at elevated temperature. SCC ...
resistance,
weldability The weldability, also known as joinability,. of a material refers to its ability to be welded. Many metals and thermoplastics can be welded, but some are easier to weld than others (see Rheological weldability). A material's weldability is used to ...
,
deformation behavior,
resistance to
radiation damage
Radiation damage is the effect of ionizing radiation on physical objects including non-living structural materials. It can be either detrimental or beneficial for materials.
Radiobiology is the study of the action of ionizing radiation on livin ...
, and
magnetic susceptibility
In electromagnetism, the magnetic susceptibility (Latin: , "receptive"; denoted ) is a measure of how much a material will become magnetized in an applied magnetic field. It is the ratio of magnetization (magnetic moment per unit volume) to the ap ...
can be highly dependent on the material’s texture and related changes in
microstructure
Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material (such as metals, polymers ...
. In many materials, properties are texture-specific, and development of unfavorable textures when the material is fabricated or in use can create weaknesses that can initiate or exacerbate failures.
Parts can fail to perform due to unfavorable textures in their component materials.
Failures can correlate with the crystalline textures formed during fabrication or use of that component.
Consequently, consideration of textures that are present in and that could form in engineered components while in use can be a critical when making decisions about the
selection
Selection may refer to:
Science
* Selection (biology), also called natural selection, selection in evolution
** Sex selection, in genetics
** Mate selection, in mating
** Sexual selection in humans, in human sexuality
** Human mating strateg ...
of some materials and
methods
Method ( grc, μέθοδος, methodos) literally means a pursuit of knowledge, investigation, mode of prosecuting such inquiry, or system. In recent centuries it more often means a prescribed process for completing a task. It may refer to:
*Scien ...
employed to manufacture parts with those materials.
When parts fail during use or abuse, understanding the textures that occur within those parts can be crucial to meaningful interpretation of
failure analysis Failure analysis is the process of collecting and analyzing data to determine the cause of a failure, often with the goal of determining corrective actions or liability.
According to Bloch and Geitner, ”machinery failures reveal a reaction chain o ...
data.
Thin film textures
As the result of substrate effects producing preferred crystallite orientations, pronounced textures tend to occur in
thin films
A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ap ...
.
Highly oriented TiO2 films on quartz substrates
Surface coatings and technology Modern technological devices to a large extent rely on polycrystalline
A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains.
Bacillite is a type of crystallite. It is rodlike with parallel longulites.
Stru ...
thin films with thicknesses in the nanometer and micrometer ranges. This holds, for instance, for all microelectronic
Microelectronics is a subfield of electronics. As the name suggests, microelectronics relates to the study and manufacture (or microfabrication) of very small electronic designs and components. Usually, but not always, this means micrometre-sc ...
and most optoelectronic
Optoelectronics (or optronics) is the study and application of electronic devices and systems that find, detect and control light, usually considered a sub-field of photonics. In this context, ''light'' often includes invisible forms of radiatio ...
systems or sensor
A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon.
In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
ic and superconducting
Superconductivity is a set of physical properties observed in certain materials where Electrical resistance and conductance, electrical resistance vanishes and magnetic field, magnetic flux fields are expelled from the material. Any material e ...
layers. Most thin film textures may be categorized as one of two different types: (1) for so-called fiber textures the orientation of a certain lattice plane is preferentially parallel to the substrate plane; (2) in biaxial textures the in-plane orientation of crystallites also tend to align with respect to the sample. The latter phenomenon is accordingly observed in nearly epitaxial
Epitaxy refers to a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epit ...
growth processes, where certain crystallographic axes of crystals in the layer tend to align along a particular crystallographic orientation of the (single-crystal) substrate.
Tailoring the texture on demand has become an important task in thin film technology. In the case of oxide compounds intended for transparent conducting film
Transparent conducting films (TCFs) are thin films of optically transparent and electrically conductive material. They are an important component in a number of electronic devices including liquid-crystal displays, OLEDs, touchscreens and phot ...
s or surface acoustic wave
A surface acoustic wave (SAW) is an acoustic wave traveling along the surface of a material exhibiting elasticity, with an amplitude that typically decays exponentially with depth into the material, such that they are confined to a depth of abou ...
(SAW) devices, for instance, the polar axis should be aligned along the substrate normal. Another example is given by cables from high-temperature superconductors
High-temperature superconductors (abbreviated high-c or HTS) are defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen. The adjective "high temperature" is only in respect to previo ...
that are being developed as oxide multilayer systems deposited on metallic ribbons. The adjustment of the biaxial texture in YBa2Cu3O7−δ layers turned out as the decisive prerequisite for achieving sufficiently large critical currents.
The degree of texture is often subjected to an evolution during thin film growth and the most pronounced textures are only obtained after the layer has achieved a certain thickness. Thin film growers thus require information about the texture profile or the texture gradient in order to optimize the deposition process. The determination of texture gradients by x-ray scattering
X-ray scattering techniques are a family of non-destructive analytical techniques which reveal information about the crystal structure, chemical composition, and physical properties of materials and thin films. These techniques are based on observ ...
, however, is not straightforward, because different depths of a specimen contribute to the signal. Techniques that allow for the adequate deconvolution of diffraction intensity were developed only recently.
References
Further reading
* Bunge, H.-J. "Mathematische Methoden der Texturanalyse" (1969) Akademie-Verlag, Berlin
* Bunge, H.-J. "Texture Analysis in Materials Science" (1983) Butterworth, London
* Kocks, U. F., Tomé, C. N., Wenk, H.-R., Beaudoin, A. J., Mecking, H. "Texture and Anisotropy – Preferred Orientations in Polycrystals and Their Effect on Materials Properties" (2000) Cambridge University Press
* Birkholz, M., chapter 5 o
"Thin Film Analysis by X-ray Scattering"
(2006) Wiley-VCH, Weinheim
External links
aluMatter: Representing Texture
MTEX MATLAB toolbox for Texture Analysis
Labotex, ODF/texture analysis software for Microsoft Windows
Combined Analysis
{{DEFAULTSORT:Texture (Crystalline)
Crystallography
Metallurgy
Materials science
Neutron-related techniques
Petrology concepts
Synchrotron-related techniques