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amorphous – Lacking definite form. Having no specific shape. Formless. Of no particular kind of character. Indeterminate. Having no pattern or structure. Unorganized. Occurring in a mass, as without stratification or crystalline structure. Not crystalline. Having structural components that are not clearly differentiated, as the nuclear material in certain bacteria.
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amorphous polymer – Amorphous polymers do not have melting points, but rather softening ranges. They are normally transparent. They undergo only small volume changes when solidifying from the melt, or when the solid softens and becomes fluid. This is in contrast to crystalline polymer. Also see amorphous.
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binary phase diagram – A phase diagram in which there are only two components.
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brittle fracture – Brittle fracture manifests itself as the very rapid propagation of a crack after little or no plastic deformation. The speed at which cracks propagate in brittle behavior after initiation rises rapidly from zero to limiting velocity of about one-third the speed of sound in the material. In polycrystalline materials the fracture proceeds along cleavage planes within each crystal, giving the fracture surface a granular appearance because of the change in orientation of the crystals and their cleavage planes within the matrix. Brittle fracture sometimes proceeds primarily along grain boundaries and is then called intergranular fracture.
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coring – Also known as microsegregation or interdendritic segregation.
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crystalline polymer – Crystalline polymers have considerable order to the molecules in the solid state, indicating that many of the other atoms are regularly spaced; have a true melting point with a latent heat of fusion associated with the melting and freezing process; and have a relatively large volume change during the transition from melt to solid. This is in contrast to amorphous polymer.
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ductile fracture – See ductile rupture.
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ductile rupture – Ductile rupture takes place after extensive plastic deformation. Ductile rupture proceeds by slow crack propagation resulting from the formation and coalescence of voids. The fracture surface appearance associated with dutile rupture is characteristically dull and fibrous. Three distinct stages are observed in the ductile rupture of most polycrystalline metals. First, the sample begins to "neck down" locally (necking), and small discrete cavities form in the necked region. Next, the cavities coalesce into a crack in the center of the cross section with the direction of the crack generally perpendicular to the direction of applied stress. Finally, the crack spreads to the surface of the sample along shear planes oriented at approximately 45 degrees to the direction of the tensile axis. The result of this sequence of events is often the well known cup-and-cone failure surface.
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fracture – Fracture is generally characterized as being either brittle or ductile. But, ductile fracture is usually referred to as ductile rupture.
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freezing range – The temperature difference between the liquidus and the solidus. Within the freezing range, two phases coexist: a liquid and a solid.
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grain – A portion of the material within which the arrangement of the atoms is identical.
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grain boundary – The surface that separates the individual grains; it is a narrow zone in which the atoms are not properly spaced.
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hardness – Hardness is the resistance of a material to penetration by a pointed tool. There are many hardness-measuring systems. Two of the most common are Brinell hardness and Rockwell hardness.
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hot shortness – Melting of the lower melting point interdendritic material at temperatures below the equilibrium solidus.
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interdendritic segregation – Also known as microsegregation or coring.
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miscibility gap – A phase region in which two or more liquid phases coexist; for example, for two different liquids L1 and L2, the miscibility gap might contain both L1 and L2.
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modulus of rupture – Same as flexural strength.
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segregation – The nonuniform composition produced by nonequilibrium solidification. Two types of segregation are microsegregation and macrosegregation.
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sublime – When a solid goes directly to a vapor without melting when it is heated. It is a verb.
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tensile strength – The stress obtained at the highest applied force, which is the maximum stress on the engineering stress-strain curve. The stress that corresponds to the maximum load in a tensile test. The term is commonly used in material science and metallurgy. Same as ultimate strength.
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tilt boundary – An angle boundary formed by an edge dislocation.
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transverse rupture strength – Same as flexural strength. Transverse rupture strength may be abbreviated TRS
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twist boundary – An angle boundary caused by a screw dislocation.
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unary – One Component
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work hardening – A term sometimes used instead of strain hardening or cold working to describe the effect of deformation on strengthening of materials.
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