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| metals that exist in the solid state in two or more lattice forms, with the particular form depending on the conditions of temperature and pressure (aka polymorphic) |
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| materials composed of two or more different elements, and they tend to exhibit their own characteristic properties. |
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| atoms have a certain degree of local order, but when viewed as an aggregate, lack the periodically ordered arrangement of atoms that is a characteristic of a crystalline solid; glass is an example |
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| properties that vary with direction. |
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| (American Society for Testing Materials) N=2^(n-1) where N is the number of grains per square inch visible in a prepared specimen at 100X and n is the ASTM grain-size number. Low ASTM numbers mean a few massive grains, while high numbers refer to materials with many small grains. |
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| the number of electrons surrounding he nucleus of a neutral atom |
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| the equilibrium separation distance between neighboring atoms can be taken as a the sum of the atomic radii, and atoms can be assigned a distinct size. Removing electrons from the outer shell will decrease atomic radius, and adding electrons will increase it. |
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| an atom is inserted in the center of the cube; each atom has 8 nearest neighbors, 68% of the space is occupied, offers high engineering strength, no close-packed planes. |
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| failure that occurs before the onset of plastic deformation; more common in metals have the BCC or HCP crystal structures |
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| structures consist of layers of close-packed planes where each layer or plane has the same configuration of identical neighboring electrons (12—six within the plane and three from each of the layers above and below); 74% efficiency of occupying space |
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| the process when metals are plastically deformed at temperature below their recrystallization temperature. |
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| electron sharing; adjacent atoms share outer-shell electrons so that each achieves a stable electron configuration. Characteristics: high strength, high melting point, brittle, range from conductive or semiconductive. |
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| a deformation that may occur on alternative systems that offer less resistance. |
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| geometric lattice that metals assume when they solidify; regular and periodic arrangement of atoms in space. |
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| deformation as a result of progressive slippage of a localized disruption. 3 types: edge, screw, mixed. |
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| process where the electrical conductivity of intrinsic semiconductors can be substantially improved |
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| when plastic deformations precedes the break |
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| the net movement of charge through the material. |
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| materials doped by leaving an additional valence electron that is free to move about and provide additional conductivity. |
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| sequence that produces a structure that can be viewed as an expanded cube with an atom inserted in the center of each of the six cube faces; preferred structure for many engineering metals, high ductility; 4 close-packed planes |
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| small, continuous volumes of solid |
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| the surfaces that divide grains (i.e. the surfaces of crystalline discontinuity) |
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| recrystallization process which tends to produce uniform grains of comparatively small size. If the metal is held at or above the recrystallization temperature, the grains in the new structure will continue to increase in size. |
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| varies in a metal with the rate of nucleation and the rate of growth. The greater the nucleation rate, the small the resulting grains. The greater the rate growth, the large the grain. |
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| packed—structure made up of identifiable closed-packed planes; poor ductility, fail in a brittle manner |
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| deformation process when the temperature of deformation is sufficiently above the recrystallization temperature. |
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the atoms of the alloying element interact with the atoms of the base metal in definite proportions and in definite geometric relationships.
• Interstitial—the alloy element atoms squeeze into the open spaces between the atoms in the base metal lattice. |
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| material where moderate amounts of thermal energy enable it to conduct small amount of electricity |
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| a negatively or positively charged atom due to the number of electrons |
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| the simples of all bonds; if more than one type of atom is present, the outermost electrons can break free from atoms with excesses in their valence shell, transforming them into positive ions. The electrons are then transferred to atoms with deficiencies in their outer shell, converting them into negative ions. The positive and negative ions have an electrostatic attraction for each other resulting in a strong bonding force. Characteristics: high strength, high hardness, brittleness, high melting point, and low electrical conductivity |
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| properties that are uniform in all directions |
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| crystalline structure where atoms are arranged in a regular geometric array, as in solid metals and most minerals. |
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| occurs when a complete outer shell cannot be formed by either electron transfer or electron sharing. If each of the atoms in an aggregate contains only a few valence electrons (1,2, or 3), these electrons can easily be removed to produce “stable” ions. The positive ions then arrange in a periodic array, and are surrounded by wandering, universally shared valence electrons. Characteristics: high electrical and thermal conductivity, ductile. |
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| another level of structure produced by, the size, shape, and arrangement of multiple crystals, or the mixture of two or more different structures within a material. |
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| have a distinct number of atoms that are held together by primary bonds. There is only a weak attraction between a given molecule and other similar groupings. |
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| the process by which a grain structure is produced upon solidification |
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| the ratio of lateral contraction to axial tensile strain. This value is always less the 0.5 and is usually about 0.3. |
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| metals that exist in the solid state in two or more lattice forms, with the particular form depending on the conditions of temperature and pressure (aka allotropic) |
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| the process of reducing the internal energy through the formation of new crystals. |
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| this structure can be constructed by placing single atoms on all corners of a cube and then linking identical cube units together. Each atom is in contact with 6 neighboring atoms, and 52% available space is occupied. |
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| the resulting shear deformation of a slip system. |
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| the specific combination of plane and direction |
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| occurs when two elements exhibit some degree of solubility in the solid state. The two materials form a solid solution, where the alloy element dissolves in the base metal. |
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| plastic deformation that causes most metals to become stronger (aka work hardening). |
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| some atoms of the alloy element occupy lattice sites normally filled by atoms of the base metal lattice |
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| unit building block that is essentially duplicated throughout space in a repetitive manner. |
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| missing atom that is a barrier to dislocation |
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| electrons in the outermost shell or subshell |
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| weak or secondary bonds; can form between molecules that possess a nonsymmetrical distribution of charge. |
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| plastic deformation that causes most metals to become stronger (aka strain hardening). |
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