Texture (chemistry)

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Pole figures displaying crystallographic texture of gamma-TiAl in an alpha2-gamma alloy, as measured by high energy X-rays. MAUD-MTEX-TiAl-hasylab-2003-Liss.png
Pole figures displaying crystallographic texture of gamma-TiAl in an alpha2-gamma alloy, as measured by high energy X-rays.

In physical chemistry [ unreliable source? ] and materials science, texture is the distribution of crystallographic orientations of a polycrystalline sample (it is also part of the geological fabric). 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.

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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. 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. [2] [3] [4] Also, geologic 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 properties at length scales sufficiently larger than the size of the crystallites. The opposite extreme is a perfect single crystal, which likely has anisotropic properties by geometric necessity.

Characterization and representation

Texture can be determined by various methods. [5] 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 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 and synchrotron high-energy X-ray diffraction are suitable for determining textures of bulk materials and in situ analysis, whereas laboratory x-ray diffraction instruments are more appropriate for analyzing textures of thin films.

Texture is often represented using a pole figure, in which a specified crystallographic 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).

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 for simplification purposes.

Orientation distribution function

The full 3D representation of crystallographic texture is given by the orientation distribution function (ODF) which can be achieved through evaluation of a set of pole figures or diffraction patterns. Subsequently, all pole figures can be derived from the ODF.

The ODF is defined as the volume fraction of grains with a certain orientation .

The orientation is normally identified using three Euler angles. 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 ODF.

The orientation distribution function, ODF, cannot be measured directly by any technique. Traditionally both X-ray diffraction and EBSD may collect pole figures. Different methodologies exist to obtain the ODF from the pole figures or data in general. They can be classified based on how they represent the ODF. Some represent the ODF as a function, sum of functions or expand it in a series of harmonic functions. Others, known as discrete methods, divide the ODF space in cells and focus on determining the value of the ODF in each cell.

Origins

Scan of sectioned, forged connecting rod that has been etched to show grain flow. ForgedConrodShowingEtchedSection-s.jpg
Scan of sectioned, forged connecting rod that has been etched to show grain flow.

In wire and fiber, 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, which has no crystal structure, and carbon fiber, 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 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 sheet for transformer cores (to reduce magnetic hysteresis) and of aluminium cans (since deep drawing requires extreme and relatively uniform plasticity).

Texture in ceramics usually arises because the crystallites in a slurry 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 or other fluid-to-solid transitions (i.e., thin-film deposition) 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 or starting new crystals of random orientation. Some facets 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 blades and other creep-sensitive parts.

Texture and materials properties

Material properties such as strength, [6] chemical reactivity, [7] stress corrosion cracking resistance, [8] weldability, [9] deformation behavior, [6] [7] resistance to radiation damage, [10] [11] and magnetic susceptibility [12] can be highly dependent on the material’s texture and related changes in microstructure. 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. [6] [7] Parts can fail to perform due to unfavorable textures in their component materials. [7] [12] Failures can correlate with the crystalline textures formed during fabrication or use of that component. [6] [9] 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 of some materials and methods employed to manufacture parts with those materials. [6] [9] When parts fail during use or abuse, understanding the textures that occur within those parts can be crucial to meaningful interpretation of failure analysis data. [6] [7]

Thin film textures

As the result of substrate effects producing preferred crystallite orientations, pronounced textures tend to occur in thin films. [13] Modern technological devices to a large extent rely on polycrystalline thin films with thicknesses in the nanometer and micrometer ranges. This holds, for instance, for all microelectronic and most optoelectronic systems or sensoric and superconducting 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 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 films or surface acoustic wave (SAW) devices, for instance, the polar axis should be aligned along the substrate normal. [14] Another example is given by cables from high-temperature superconductors that are being developed as oxide multilayer systems deposited on metallic ribbons. [15] The adjustment of the biaxial texture in YBa2Cu3O7−δ layers turned out as the decisive prerequisite for achieving sufficiently large critical currents. [16]

The degree of texture is often subjected to an evolution during thin film growth [17] 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, 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. [18] [19]

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<span class="mw-page-title-main">Anisotropy</span> In geometry, property of being directionally dependent

Anisotropy is the structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit very different properties when measured along different axes: physical or mechanical properties.

In condensed matter physics and materials science, an amorphous solid is a solid that lacks the long-range order that is characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a glass transition. Examples of amorphous solids include glasses, metallic glasses, and certain types of plastics and polymers.

<span class="mw-page-title-main">Crystal</span> Solid material with highly ordered microscopic structure

A crystal or crystalline solid is a solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.

<span class="mw-page-title-main">Crystallography</span> Scientific study of crystal structures

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. The word crystallography is derived from the Ancient Greek word κρύσταλλος, with its meaning extending to all solids with some degree of transparency, and γράφειν. In July 2012, the United Nations recognised the importance of the science of crystallography by proclaiming that 2014 would be the International Year of Crystallography.

<span class="mw-page-title-main">Crystallite</span> Small crystal which forms under certain conditions

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.

Reflection high-energy electron diffraction (RHEED) is a technique used to characterize the surface of crystalline materials. RHEED systems gather information only from the surface layer of the sample, which distinguishes RHEED from other materials characterization methods that also rely on diffraction of high-energy electrons. Transmission electron microscopy, another common electron diffraction method samples mainly the bulk of the sample due to the geometry of the system, although in special cases it can provide surface information. Low-energy electron diffraction (LEED) is also surface sensitive, but LEED achieves surface sensitivity through the use of low energy electrons.

<span class="mw-page-title-main">Electron backscatter diffraction</span> Scanning electron microscopy technique

Electron backscatter diffraction (EBSD) is a scanning electron microscopy (SEM) technique used to study the crystallographic structure of materials. EBSD is carried out in a scanning electron microscope equipped with an EBSD detector comprising at least a phosphorescent screen, a compact lens and a low-light camera. In the microscope an incident beam of electrons hits a tilted sample. As backscattered electrons leave the sample, they interact with the atoms and are both elastically diffracted and lose energy, leaving the sample at various scattering angles before reaching the phosphor screen forming Kikuchi patterns (EBSPs). The EBSD spatial resolution depends on many factors, including the nature of the material under study and the sample preparation. They can be indexed to provide information about the material's grain structure, grain orientation, and phase at the micro-scale. EBSD is used for impurities and defect studies, plastic deformation, and statistical analysis for average misorientation, grain size, and crystallographic texture. EBSD can also be combined with energy-dispersive X-ray spectroscopy (EDS), cathodoluminescence (CL), and wavelength-dispersive X-ray spectroscopy (WDS) for advanced phase identification and materials discovery.

<span class="mw-page-title-main">Powder diffraction</span>

Powder diffraction is a scientific technique using X-ray, neutron, or electron diffraction on powder or microcrystalline samples for structural characterization of materials. An instrument dedicated to performing such powder measurements is called a powder diffractometer.

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 planes in crystallography and texture analysis in materials science.

<span class="mw-page-title-main">Selected area diffraction</span>

Selected area (electron) diffraction is a crystallographic experimental technique typically performed using a transmission electron microscope (TEM). It is a specific case of electron diffraction used primarily in material science and solid state physics as one of the most common experimental techniques. Especially with appropriate analytical software, SAD patterns (SADP) can be used to determine crystal orientation, measure lattice constants or examine its defects.

<span class="mw-page-title-main">Fiber diffraction</span> Subarea of scattering, an area in which molecular structure is determined from scattering data

Fiber diffraction is a subarea of scattering, an area in which molecular structure is determined from scattering data. In fiber diffraction the scattering pattern does not change, as the sample is rotated about a unique axis. Such uniaxial symmetry is frequent with filaments or fibers consisting of biological or man-made macromolecules. In crystallography fiber symmetry is an aggravation regarding the determination of crystal structure, because reflexions are smeared and may overlap in the fiber diffraction pattern. Materials science considers fiber symmetry a simplification, because almost the complete obtainable structure information is in a single two-dimensional (2D) diffraction pattern exposed on photographic film or on a 2D detector. 2 instead of 3 co-ordinate directions suffice to describe fiber diffraction.

<span class="mw-page-title-main">Texture (geology)</span>

In geology, texture or rock microstructure refers to the relationship between the materials of which a rock is composed. The broadest textural classes are crystalline, fragmental, aphanitic, and glassy. The geometric aspects and relations amongst the component particles or crystals are referred to as the crystallographic texture or preferred orientation. Textures can be quantified in many ways. The most common parameter is the crystal size distribution. This creates the physical appearance or character of a rock, such as grain size, shape, arrangement, and other properties, at both the visible and microscopic scale.

Diffraction topography is a imaging technique based on Bragg diffraction. Diffraction topographic images ("topographies") record the intensity profile of a beam of X-rays diffracted by a crystal. A topography thus represents a two-dimensional spatial intensity mapping of reflected X-rays, i.e. the spatial fine structure of a Laue reflection. This intensity mapping reflects the distribution of scattering power inside the crystal; topographs therefore reveal the irregularities in a non-ideal crystal lattice. X-ray diffraction topography is one variant of X-ray imaging, making use of diffraction contrast rather than absorption contrast which is usually used in radiography and computed tomography (CT). Topography is exploited to a lesser extends with neutrons, and has similarities to dark field imaging in the electron microscope community.

<span class="mw-page-title-main">Sputter deposition</span> Method of thin film application

Sputter deposition is a physical vapor deposition (PVD) method of thin film deposition by the phenomenon of sputtering. This involves ejecting material from a "target" that is a source onto a "substrate" such as a silicon wafer. Resputtering is re-emission of the deposited material during the deposition process by ion or atom bombardment. Sputtered atoms ejected from the target have a wide energy distribution, typically up to tens of eV. The sputtered ions can ballistically fly from the target in straight lines and impact energetically on the substrates or vacuum chamber. Alternatively, at higher gas pressures, the ions collide with the gas atoms that act as a moderator and move diffusively, reaching the substrates or vacuum chamber wall and condensing after undergoing a random walk. The entire range from high-energy ballistic impact to low-energy thermalized motion is accessible by changing the background gas pressure. The sputtering gas is often an inert gas such as argon. For efficient momentum transfer, the atomic weight of the sputtering gas should be close to the atomic weight of the target, so for sputtering light elements neon is preferable, while for heavy elements krypton or xenon are used. Reactive gases can also be used to sputter compounds. The compound can be formed on the target surface, in-flight or on the substrate depending on the process parameters. The availability of many parameters that control sputter deposition make it a complex process, but also allow experts a large degree of control over the growth and microstructure of the film.

A crystallographic database is a database specifically designed to store information about the structure of molecules and crystals. Crystals are solids having, in all three dimensions of space, a regularly repeating arrangement of atoms, ions, or molecules. They are characterized by symmetry, morphology, and directionally dependent physical properties. A crystal structure describes the arrangement of atoms, ions, or molecules in a crystal.

In materials science, misorientation is the difference in crystallographic orientation between two crystallites in a polycrystalline material.

<span class="mw-page-title-main">SRAS</span>

SRAS a non-destructive acoustic microscopy microstructural-crystallographic characterization technique commonly used in the study of crystalline or polycrystalline materials. The technique can provide information about the structure and crystallographic orientation of the material. Traditionally, the information provided by SRAS has been acquired by using diffraction techniques in electron microscopy - such as EBSD. The technique was patented in 2005, EP patent 1910815.

In condensed matter physics and continuum mechanics, an isotropic solid refers to a solid material for which physical properties are independent of the orientation of the system. While the finite sizes of atoms and bonding considerations ensure that true isotropy of atomic position will not exist in the solid state, it is possible for measurements of a given property to yield isotropic results, either due to the symmetries present within a crystal system, or due to the effects of orientational averaging over a sample. Isotropic solids tend to be of interest when developing models for physical behavior of materials, as they tend to allow for dramatic simplifications of theory; for example, conductivity in metals of the cubic crystal system can be described with single scalar value, rather than a tensor. Additionally, cubic crystals are isotropic with respect to thermal expansion and will expand equally in all directions when heated.

Three-dimensional X-ray diffraction (3DXRD) is a microscopy technique using hard X-rays to investigate the internal structure of polycrystalline materials in three dimensions. For a given sample, 3DXRD returns the shape, juxtaposition, and orientation of the crystallites ("grains") it is made of. 3DXRD allows investigating micrometer- to millimetre-sized samples with resolution ranging from hundreds of nanometers to micrometers. Other techniques employing X-rays to investigate the internal structure of polycrystalline materials include X-ray diffraction contrast tomography (DCT) and high energy X-ray diffraction (HEDM).

Hans-Rudolf Wenk is a Swiss mountaineer, vintner, mineralogist, crystallographer and geologist.

References

  1. ↑ Liss KD, Bartels A, Schreyer A, Clemens H (2003). "High energy X-rays: A tool for advanced bulk investigations in materials science and physics". Textures Microstruct. 35 (3/4): 219–52. doi: 10.1080/07303300310001634952 .
  2. ↑ Bahl, Sumit; Nithilaksh, P. L.; Suwas, Satyam; Kailas, Satish V.; Chatterjee, Kaushik (2017). "Processing–Microstructure–Crystallographic Texture–Surface Property Relationships in Friction Stir Processing of Titanium". Journal of Materials Engineering and Performance. 26 (9): 4206–4216. Bibcode:2017JMEP...26.4206B. doi:10.1007/s11665-017-2865-6. ISSN   1059-9495. S2CID   139263116.
  3. ↑ Proceedings of the International Conference on microstructure and texture in steels and other materials ; February 5-7, 2008, Jamshedpur, India. Arunansu Haldar, Satyam Suwas, Debashish Bhattacharjee, Tata Iron and Steel Company, Indian Institute of Metals. London: Springer. 2009. ISBN   978-1-84882-454-6. OCLC   489216165.{{cite book}}: CS1 maint: others (link)
  4. ↑ Murty, S. V. S. Narayana; Nayan, Niraj; Kumar, Pankaj; Narayanan, P. Ramesh; Sharma, S. C.; George, Koshy M. (2014-01-01). "Microstructure–texture–mechanical properties relationship in multi-pass warm rolled Ti–6Al–4V Alloy". Materials Science and Engineering: A. 589: 174–181. doi:10.1016/j.msea.2013.09.087. ISSN   0921-5093.
  5. ↑ H.-R. Wenk & P. Van Houtte (2004). "Texture and anisotropy". Rep. Prog. Phys. 67 (8): 1367–1428. Bibcode:2004RPPh...67.1367W. doi:10.1088/0034-4885/67/8/R02. S2CID   250741723.
  6. 1 2 3 4 5 6 O. Engler & V. Randle (2009). Introduction to Texture Analysis: Macrotexture, Microtexture, and Orientation Mapping, Second Edition. CRC Press. ISBN   978-1-4200-6365-3.
  7. 1 2 3 4 5 U. F. Kocks, C. N. Tomé, H. -R. Wenk and H. Mecking (2000). Texture and Anisotropy: Preferred Orientations in Polycrystals and their effects on Materials Properties. Cambridge University Press. ISBN   978-0-521-79420-6.{{cite book}}: CS1 maint: multiple names: authors list (link)
  8. ↑ D. B. Knorr, J. M. Peltier, and R. M. Pelloux, "Influence of Crystallographic Texture and Test Temperature on Initiation and Propagation of Iodine Stress-Corrosion Cracks in Zircaloy" (1972). Zirconium in the Nuclear Industry: Sixth International Symposium. Philadelphia, PA: ASTM. pp. 627–651.{{cite book}}: CS1 maint: multiple names: authors list (link)
  9. 1 2 3 Peter Rudling; A. Strasser & F. Garzarolli. (2007). Welding of Zirconium Alloys (PDF). Sweden: Advanced Nuclear Technology International. pp. 4–3(4–13).
  10. ↑ Y. S. Kim; H. K. Woo; K. S. Im & S. I. Kwun (2002). The Cause for Enhanced Corrosion of Zirconium Alloys by Hydrides. Philadelphia, PA: ASTM. p. 277. ISBN   978-0-8031-2895-8.{{cite book}}: |journal= ignored (help)
  11. ↑ Brachet J.; Portier L.; Forgeron T.; Hivroz J.; Hamon D.; Guilbert T.; Bredel T.; Yvon P.; Mardon J.; Jacques P. (2002). Influence of Hydrogen Content on the α/β Phase Transformation Temperatures and on the Thermal-Mechanical Behavior of Zy-4, M4 (ZrSnFeV), and M5™ (ZrNbO) Alloys During the First Phase of LOCA Transient. Philadelphia, PA: ASTM. p. 685. ISBN   978-0-8031-2895-8.{{cite book}}: |journal= ignored (help)
  12. 1 2 B. C. Cullity (1956). Elements of X-Ray Diffraction . United States of America: Addison-Wesley. pp.  273–274.
  13. ↑ Highly oriented TiO2 films on quartz substrates Surface coatings and technology
  14. ↑ M. Birkholz, B. Selle, F. Fenske and W. Fuhs (2003). "Structure-Function Relationship between Preferred Orientation of Crystallites and Electrical Resistivity in Thin Polycrystalline ZnO:Al Films". Phys. Rev. B. 68 (20): 205414. Bibcode:2003PhRvB..68t5414B. doi:10.1103/PhysRevB.68.205414.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  15. ↑ A. Goyal, M. Parans Paranthaman and U. Schoop (2004). "The RABiTS Approach: Using Rolling-Assisted Biaxially Textured Substrates for High-Performance YBCO Superconductors". MRS Bull. 29 (August): 552–561. doi:10.1557/mrs2004.161. S2CID   137596044.
  16. ↑ Y. Iijima, K. Kakimoto, Y. Yamada, T. Izumi, T. Saitoh and Y. Shiohara (2004). "Research and Development of Biaxially Textured IBAD-GZO Templates for Coated Superconductors". MRS Bull. 29 (August): 564–571. doi:10.1557/mrs2004.162. S2CID   138727993.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ↑ F. Fenske, B. Selle, M. Birkholz (2005). "Preferred Orientation and Anisotropic Growth in Polycrystalline ZnO:Al Films Prepared by Magnetron Sputtering". Jpn. J. Appl. Phys. Lett. 44 (21): L662–L664. Bibcode:2005JaJAP..44L.662F. doi:10.1143/JJAP.44.L662. S2CID   59069596.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  18. ↑ J. Bonarski (2006). "X-ray texture tomography of near-surface areas". Progress in Materials Science. 51: 61–149. doi:10.1016/j.pmatsci.2005.05.001.
  19. ↑ M. Birkholz (2007). "Modelling of diffraction from fiber texture gradients in thin polycrystalline films". J. Appl. Crystallogr. 40 (4): 735–742. Bibcode:2007JApCr..40..735B. doi:10.1107/S0021889807027240.

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