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Strengthening In Aluminum Alloys

  1. Apr 1, 2008 #1
    Hi everyone!

    I have a question about mechanical properties of the materials. As I understand, when in metals microstructure the grains size decreases, the mechanical properties increases, specially metals strengthening.
    But I have a discussion with one Prof. who says that this is a minor eefect in Al alloys as compare to the steels. In Al only an Orowan mechanism works. In this mechanism, the dislocation bends between the particles leaving a dislocation ring about each particle.

    Is he right? Anyone can help me to find the strengthening mechanism in metals.

    Thanks a lot.
     
  2. jcsd
  3. Apr 1, 2008 #2

    Mapes

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    Your understanding is correct; grain size influences yield strength. (Anything that impedes dislocation motion in ductile polycrystalline materials increases strength.) However, perhaps your professor is saying that in a particular alloy, particle strengthening is so effective that changing grain size has little effect. Do you know what alloy he or she had in mind?
     
  4. Apr 1, 2008 #3
    He means all kinds of aluminium as compare to steel where grain size have a big influence to its mechanical properties.
     
  5. Apr 1, 2008 #4

    Mapes

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    See here for a brief discussion in the Handbook of Aluminum.
     
  6. Apr 2, 2008 #5
    Rasputin,

    Your professor must be nuts! When grains get down to the sub-micron level grain size most certainly will effect yielding. Dislocation pileup is a real effect and has been observed on TEM. Making blanket statements like that in Material Science is wrong!

    modey3
     
  7. Apr 10, 2008 #6
    Modey3, Thanks, I got this book and seems very good with good theories and their explaining.
     
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