Exam II Vocabulary

Exam II Vocabulary - Exam II Vocabulary Chapter 4 Alloy a...

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Exam II Vocabulary Chapter 4 Alloy – a metallic substance composed of two or more elements –pg. 83 Atom percent – concentration specification on the basis of the number of moles (or atoms) relative to the total number of moles (or atoms) of all elements within an alloy. Differs from weight percent because of density. –pr. 85 Atomic Vibration – the vibration of an atom about its normal position in a substance, these atomic vibrations may be thought of as imperfections or defects. At any instant not all atoms vibrate at the same frequency, amplitude, or energy, but as temperature increases the average energy increases. –pg. 96 Boltzmann’s Constant (k) – a thermal energy constant. –pg. 82 k = 1.38 x 10 -23 J/(atom-K) k = 8.62 x 10 -5 eV/(atom-K) Burgers vector (b) – a vector that denotes the magnitude and direction of lattice distortion associated with a edge, screw, or mixed dislocation. For an edge dislocation, they are perpendicular. Screw, they are parallel, and neither for mixed. –pg. 89, Figures Composition – the relative content of a particular element or constituent within an alloy, usually expressed in weight percent or atom percent. –pg. 85 Dislocation Line – the line that extends along the end of the extra half-plane of atoms for an edge dislocation, and along the center of the spiral of a screw dislocation. –pg. 88 Edge Dislocation – an extra portion of plane atoms, or half-plane, the edge of which terminates within the crystal A linear crystal-line defect associated with the lattice distortion produced in the vicinity of the end of an extra half-plane of atoms within a crystal. The Burgers vector is perpendicular to the dislocation line. –pg. 88 Grain Size – the average grain diameter as determined from a random cross section. The Imperfection – a deviation from atomic/ molecular order and or continuity, this could be a different kind of atom or a hole. –pg. 81 Interstitial solid solution – Impurity atoms fill the voids or interstices among the host atoms. For metallic materials that have relatively high atomic packing factors, these interstitial positions are relatively small. Therefore, the atomic diameter of an interstitial impurity must be substantially smaller than that of the host atoms. –pg. 84 Microscopy – the investigation of micro-structural elements using some type of microscope (optical, electron, scanning probe microscopes). –pg. 97 Microstructure – the structural feartures of an alloy (grain, phase structure…) that are subject to observation under a microscope. –pg. 97 Mixed dislocation – a dislocation that has both edge and screw components. –pg. 89, Figure 4.5 Photomicrograph – The photo made with a microscope, which records a microstructural image. –pg. 97 Point defect – Defects associated with one or two atomic positions. Include vacancies, self-interstitials, and impurities in solids. –pg. 81
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This note was uploaded on 09/29/2008 for the course ENGR 30014 taught by Professor Kolesar during the Spring '08 term at TCU.

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Exam II Vocabulary - Exam II Vocabulary Chapter 4 Alloy a...

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