Material Science

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Author:
ereim
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33807
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Material Science
Updated:
2010-09-13 09:59:50
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Chapter1 Structures Metals
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Chapter1 Structures of Metals
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  1. A mixture of two or more materials, at least one of which is a metal
    Alloy
  2. The unit cell consists of eight atoms at the corners of a cube and one atom at the body center of the cube
    Body-centered cubic structure
  3. An alloy composed of secondary crystals imbedded in a primary polycrystalline matrix. (does not necessarily imply that the component materials are metals).
    Composite
  4. The permanent deformation of a metal that increases with time under constant load or stress. Becomes progressively easier with increasing temperature.
    Creep
  5. The atoms of a metal are arranged in a three-dimensional array called a lattice. The lattice has a regular repeating configuration in all directions.
    Crystal structure
  6. The unit cell consists of eight atoms at the corners of a cube and one atom at the center of each of the faces of the cube
    Face-centered cubic structure
  7. A crystal, which is the region of space occupied by a continuous crystal lattice
    Grain
  8. Refers to the outside area of a grain that separates it from the other grains. A region of misfit between the grains and is usually one to three atom diameters wide
    Grain boundary
  9. Refers to the arrangement of the grains in a metal, with a grain having a particular crystal structure
    Grain structure
  10. The unit cell consists of three layers of atoms. The top and bottom layers contain six atoms at the corners of a hexagon and one atom at the center of each hexagon. The middle layer contains three atoms nestled between the atoms of the top and bottom layers, hence, the name close-packed
    Hexagonal close-packed (HCP) arrangement
  11. Refers to locations between atoms in a lattice structure
    Interstitial
  12. Results from an impurity located at an interstitial site or one of the lattice atoms being in an interstitial position instead of being at its lattice position
    Interstitial defect
  13. Consisting of crystals that are variously oriented (composed of more than one crystal).
    Polycrystalline
  14. The property or ability of a metal to exist in two or more crystalline forms, depending upon temperature and composition
    Polymorphism
  15. A force applied to a metal that causes planes of atoms within the crystal structure to move in relation to adjacent planes of atoms
    Slip
  16. Result from an impurity present at a lattice position.
    Substitutional defects
    • Body Center Cubic (BCC)
    • High Strength
    • Low Ductility
    • Face Centered Cubic (FCC)
    • Low Strength
    • High Ductility
    • Hexagonal Closed Package (HCP)
    • High Strength
    • Low Ductility
  17. STATE the five types of bonding that occur in materials and their characteristics
    • Ionic bond - In this type of bond, one or more electrons are wholly transferred from an atom of one element to the atom of the other, and the elements are held together by the force of attraction due to the opposite polarity of the resultant charges.
    • Covalent bond - A bond formed by elements sharing electrons. Electrons are shared when an atom needs electrons to complete its outer shell and can share those electrons with its neighbor. The electrons are then part of both atoms and both shells are filled.
    • Metallic bond - In this type of bond, the atoms do not share or exchange electrons to bond together. Instead, many electrons (roughly one for each atom) are more or less free to move throughout the metal, so that each electron can interact with many of the fixed atoms.
    • Molecular bond - When the electrons of neutral atoms spend more time in one region of their orbit, a temporary weak charge will exist. The molecule will weakly attract other molecules. This is sometimes also called a Van der Waal bond.
    • Hydrogen bond - This bond is similar to the molecular bond and occurs due to the ease with which hydrogen atoms are willing to give up an electron to atoms of oxygen, fluorine, or nitrogen.
  18. DEFINE Crystal Structure
    The atoms of a metal are arranged in a three-dimensional array called a lattice. The lattice has a regular repeating configuration in all directions. A group of particles from one part of a crystal has exactly the same geometric relationship as a group from any other part of the same crystal
  19. IDENTIFY the polymorphism phase that prevents pure uranium from being used as fuel.
    Alpha Phase - Heating and cooling of alpha phase uranium can lead to drastic dimensional changes and gross distortions of the metal. Thus, pure uranium is not used as a fuel.
  20. IDENTIFY the three types of microscopic imperfections found in crystalline structures
    • Point imperfections have atomic dimensions.
    • Line imperfections or dislocations are generally many atoms in length.
    • Interfacial imperfections are larger than line defects and occur over a two-dimensional area.
  21. STATE how slip occurs in crystals
    A slip occurs when the crystal is subjected to a stress, and the dislocation moves through the crystal until it reaches the edge or is stopped by another dislocation
  22. IDENTIFY the four types of bulk defects
    • Foreign Particles included in the prime material
    • Gas Pockets
    • Shrinking Cavities
    • Welding or Joining defects

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