Concise Dictionary of Materials Science Part 2 pdf

tion, at various t, there may be different values of the elasticity modulus, its extremities being the Young’s modulus E corresponding to the Hooke’s law at t << τ R a nd what is known as the relaxation modulus E R < E at t >> τ R . See also internal friction. anisotropic Having different physical and mechanical properties in various directions. Anisotropy of single crystals is a result of crystalline aniso- tropy, whereas that of a polycrystal is dependent on crystallographic texture (and so on the crystalline anisotropy) as well as on the microstruc - tural anisotropy as, e.g., banded structure or carbide stringers in steels or an elongated grain structure in heat-resistant alloys (see Nabarro − Herring or Coble creep). Anisotropy can be observed not only in crystal - line solids but also in some liquids (see liquid crystals). annealing/anneal Heat treatment resulting in the occurrence of equilibrium phases (see, e.g., graphitization anneal, solution annealing), in removing of deformation or amorphization effects or in attaining a required grain size or texture (see, e.g., recrystallization annealing), or in relieving chem - ical inhomogeneity and macroscopic residual stresses (see homogenizing, stress-relief annealing). In metallic alloys, annealing is a preliminary treatment preparing the microstructure or phase composition to a final treatment (see, e.g., austenitization and solution treatment). Annealing after amorphization of single-crystalline semiconductors can restore sin - gle-crystalline structure. annealing texture Preferred orientation evolved in the course of primary recrys- tallization or grain growth. Recrystallization texture occurs because recrystallization nuclei are of nonrandom orientations and grow into the deformed matrix at different rates. It can be similar to deformation texture or quite different from it. Texture changes during grain growth are con - nected with different driving forces for growth of variously oriented grains and different mobility of their boundaries (see compromise texture). Grain growth commonly (but not always) results in weakening of the primary recrystallization texture. Annealing texture is usually characterized by an increased scatter and a decreased intensity in comparison to the initial deformation texture, except for a cube texture in some cold-rolled FCC alloys and the Goss texture in ferritic steels. annealing twin Twin occurring during primary recrystallization or grain growth. Annealing twins are usually observed in materials with low stacking-fault energy, especially on annealing after heavy plastic deformation. An annealing twin, depending on its position inside a grain, can have one or two coherent twin boundaries joining up with grain boundaries or inco - herent twin boundaries. The twin with two coherent boundaries looks like a straight band. anomalous x-ray transmission Abnormally low x-ray absorption observed in thick perfect crystals adjusted at the exact Bragg angle. It is also known as the Borrmann effect. antiferromagnetic Material characterized (below Néel point) by a negative energy of exchange interaction and equal but oppositely directed magnetic © 2003 by CRC Press LLC tion, at various t, there may be different values of the elasticity modulus, its extremities being the Young’s modulus E corresponding to the Hooke’s law at t << τ R a nd what is known as the relaxation modulus E R < E at t >> τ R . See also internal friction. anisotropic Having different physical and mechanical properties in various directions. Anisotropy of single crystals is a result of crystalline aniso- tropy, whereas that of a polycrystal is dependent on crystallographic texture (and so on the crystalline anisotropy) as well as on the microstruc - tural anisotropy as, e.g., banded structure or carbide stringers in steels or an elongated grain structure in heat-resistant alloys (see Nabarro − Herring or Coble creep). Anisotropy can be observed not only in crystal - line solids but also in some liquids (see liquid crystals). annealing/anneal Heat treatment resulting in the occurrence of equilibrium phases (see, e.g., graphitization anneal, solution annealing), in removing of deformation or amorphization effects or in attaining a required grain size or texture (see, e.g., recrystallization annealing), or in relieving chem - ical inhomogeneity and macroscopic residual stresses (see homogenizing, stress-relief annealing). In metallic alloys, annealing is a preliminary treatment preparing the microstructure or phase composition to a final treatment (see, e.g., austenitization and solution treatment). Annealing after amorphization of single-crystalline semiconductors can restore sin - gle-crystalline structure. annealing texture Preferred orientation evolved in the course of primary recrys- tallization or grain growth. Recrystallization texture occurs because recrystallization nuclei are of nonrandom orientations and grow into the deformed matrix at different rates. It can be similar to deformation texture or quite different from it. Texture changes during grain growth are con - nected with different driving forces for growth of variously oriented grains and different mobility of their boundaries (see compromise texture). Grain growth commonly (but not always) results in weakening of the primary recrystallization texture. Annealing texture is usually characterized by an increased scatter and a decreased intensity in comparison to the initial deformation texture, except for a cube texture in some cold-rolled FCC alloys and the Goss texture in ferritic steels. annealing twin Twin occurring during primary recrystallization or grain growth. Annealing twins are usually observed in materials with low stacking-fault energy, especially on annealing after heavy plastic deformation. An annealing twin, depending on its position inside a grain, can have one or two coherent twin boundaries joining up with grain boundaries or inco - herent twin boundaries. The twin with two coherent boundaries looks like a straight band. anomalous x-ray transmission Abnormally low x-ray absorption observed in thick perfect crystals adjusted at the exact Bragg angle. It is also known as the Borrmann effect. antiferromagnetic Material characterized (below Néel point) by a negative energy of exchange interaction and equal but oppositely directed magnetic © 2003 by CRC Press LLC B β-Al 2 O 3 Impure alumina whose main impurity is Na 2 O. β eutectoid Ti system Name of a Ti−X alloy system in which the β-stabilizer X has a limited solubility in β-Ti, and a eutectoid reaction β ↔ α + γ takes place (γ is an intermediate phase or a terminal solid solution). β-Fe Obsolete designation of the paramagnetic α-Fe existing at temperatures between 768 and 910°C at atmospheric pressure (i.e., between A 2 a nd A 3 ). Correspondingly, a solid solution in β-Fe was named β-ferrite. β isomorphous Ti system Name of a Ti–X alloy system in which the alloying element X is the β-stabilizer and there is no eutectoid reaction in the corresponding phase diagram. β m pha se [in Ti alloys] See metastable β-phase. β-phase [in Ti alloys] Solid solution of alloying elements in β-Ti. β-stabilizer Alloying element expanding the β-phase field in phase diagrams of Ti alloys and thereby lowering β/(α + β) transus. β-Ti High-temperature allotropic form of titanium having BCC crystal structure and existing above 882°C up to the melting point at atmospheric pressure. β Ti alloy Alloy with β-stabilizers wherein β-phase is the only phase constituent after air-cooling from temperatures above the β/(α + β) transus. Alloys with a small (∼5 vol%) amount of α-phase are related to the same group and termed near-β alloys. If the β → α transition does not evolve on air- cooling, these alloys are named metastable β alloys. background In x-ray structure analysis and texture analysis, an intensity of scat- tered x-ray radiation between diffraction lines caused mainly by: x-ray flu - orescent radiation emitted by the specimen, diffraction of the white radiation on the polycrystalline specimen, Compton scattering, and diffuse scattering. back-reflection Laue method Technique wherein an x-ray source and a flat film (screen) registering an x-ray diffraction pattern are placed on the same side of the sample. backscattered electron Electron elastically scattered in the direction that is opposite to the direction of the primary beam. The yield of backscattered electrons increases with the atomic number of the substance studied. Backscattered electrons are used in SEM for gaining data on the topog - raphy, microstructure, and chemistry of the specimen surface, as well as for crystallographic studies (see electron channeling). 0970_frame_B Page 13 Friday, August 1, 2003 7:01 PM © 2003 by CRC Press LLC C χ-carbide In high-carbon steels, a transient phase of the composition Fe 5 C 2 wi th monoclinic lattice. It occurs upon tempering of as-quenched martensite. CaF 2 st ructure Crystal structure wherein Ca 2+ i ons form an FCC sublattice and F 1– i ons, occupying half the tetrahedral sites of the first one, form the second sublattice (see Figure C.1). CaF 2 is called fluorite. calorimetry Technique for studying phase transitions by measuring thermal effects, i.e., taking off or releasing the heat in the course of the transitions. See, e.g., differential scanning calorimetry. capillary driving force Driving force for migration of grain or phase bound- aries under the influence of the boundary curvature (see Gibbs–Thomson equation); this driving force is directed to the center of the curvature. In a three-dimensional, single-phase structure, it is: ∆g = γ gb (ρ 1 + ρ 2 ) where γ gb is the grain-boundary energy, and ρ 1 and ρ 2 are the principal radii of the boundary curvature. Capillary driving force promotes normal and abnormal grain growth, as well as shrinkage of porous compacts in the course of sintering. carbide In binary alloys, an intermediate phase containing carbon. In alloys with more than two components, metallic components can dissolve in binary carbides, forming complex carbides. FIGURE C.1 Unit cell of CaF 2 crystal structure. Solid and open spheres show F 1– and Ca 2+ ions, respectively. © 2003 by CRC Press LLC . energy of exchange interaction and equal but oppositely directed magnetic © 20 03 by CRC Press LLC B β-Al 2 O 3 Impure alumina whose main impurity is Na 2 O. β eutectoid Ti system Name of a. August 1, 20 03 7:01 PM © 20 03 by CRC Press LLC C χ-carbide In high-carbon steels, a transient phase of the composition Fe 5 C 2 wi th monoclinic lattice. It occurs upon tempering of as-quenched. forming complex carbides. FIGURE C.1 Unit cell of CaF 2 crystal structure. Solid and open spheres show F 1– and Ca 2+ ions, respectively. © 20 03 by CRC Press LLC