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Are blocks (billets) of metal crystals?

  1. Jul 23, 2010 #1
    I work as a machinest and Mill mostly aluminum. I was wondering if the billets are Aluminum its crystalline form? Or just lots of Aluminum atoms held together by Metallic bond?

    thank you.

    Attached is a photo of Aluminum Block.
     

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  2. jcsd
  3. Jul 23, 2010 #2
    I enjoyed the picture.
    The answer is both. Metallic bonds are when the metal atoms are held in a crystal structure, sharing a 'sea' of electrons. If you would call this a "crystalline state (form)" is semantics... and up to interpretation. A crystal structure is just a highly regular one (i.e. based on repeating units), which a metal is; a 'crystal' is generally a substance in a crystal structure, that often isn't (e.g. carbon is usually in the form of graphite, or coal, or whatever, rarely in a crystal; or quartz--which is the crystal form of silica[sand]).
     
  4. Jul 23, 2010 #3
    Thank you zhermes.

    I have always wondered about this and couldn't get the answer I wanted from the open net.

    O'yeah, are all other metal like this also?
     
  5. Jul 23, 2010 #4

    Mapes

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    The aluminum block (along with all common metals in bulk form) is http://en.wikipedia.org/wiki/Polycrystal" [Broken], made up of many individual crystals, or grains, with sizes typically 10 nm - 100 μm.
     
    Last edited by a moderator: May 4, 2017
  6. Jul 24, 2010 #5
    Not always, my old chemistry teacher was fond of pointing out the brass door pushes in the school latrine were so etched by uric acid that the grain boundaries were clearly visible.

    The grains were up to an inch across.
     
  7. Jul 24, 2010 #6

    Mapes

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    Neat!

    You can hardly find better examples of (1) corrosion and (2) probability distribution of aim than at a urinal. :eek:
     
  8. Jul 24, 2010 #7
    I think it was mainly unwashed hands.
    The trail extended several fire-doors down the corridor.
     
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