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Percipition Chart

  1. Mar 7, 2007 #1
    I'm not sure if Percipitation graph is the correct terminology for this. But I know there are charts which can show a materials hardness after percipitating over time, then once it percipitates longer than a certain amount of time, it will lose its hardness. I'm specifically looking for AA6061...

    Thanks. Kevin.
     
  2. jcsd
  3. Mar 7, 2007 #2

    Astronuc

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    Staff: Mentor

    I think you are referring to an aging diagram, and the softening, which is related to the coarsening of precipitates, is due to 'over-aging'.

    These might be of interest -

    Impact of pre-aging on the tensile and bending properties of AA 6061

    Microstructural Development and Mechanical Properties of Interrupted Aged Al-Mg-Si-Cu Alloy Check in the University library for METALLURGICAL AND MATERIALS TRANSACTIONS A.

    See also - Accelerated Methods for Characterization of Aging Response



    http://mme.iitm.ac.in/kpr/h206061.htm
     
    Last edited: Mar 7, 2007
  4. Mar 7, 2007 #3
    I'm curious how over aging a material though softens it... you would think instead it would just reach its max hardness, and stay at it no matter how long it was aged for...

    (you don't need to have all those links to answer this question, I know that takes a lot of time to do)
     
  5. Mar 8, 2007 #4
  6. Mar 9, 2007 #5

    Astronuc

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    Staff: Mentor

    See below.

    Not a problem. I find it useful for myself to collect relevant links and put them in one place - PF. :biggrin: Besides, I hope PFers find them useful.


    refering to the page - http://www.hmi.de/bereiche/SF/SF3/m...age_hardenable_aluminium_alloys/index_en.html
    It is unfortunate that this paragraph simply ends with such a simple statement "afterwards hardness decreases due to over-aging" without elaborating why that is.

    Think about the aging process - "Age-hardening first produces clusters of a few nm size which are an enrichment of the base material with its alloying elements Mg and Si" - in relationship to the composition in (Al-Mg-Si). For maximum and uniform hardness, one would want the Mg-Si clusters (intermetallic compound) small and evenly/uniformly dispersed. As the aging process continues, the clusters can grow - BUT that means that the base material becomes depleted in the Mg and Si, so what is left is an area/volume with more of the softer Al.
     
  7. Mar 9, 2007 #6
    I guess you can think of it as being compared to us. We start off young.. we grow... our strength naturally will increase as we get older... once we reach a certain age range, we are at our peaks... then we keep getting older, and we get weaker.. lol
     
  8. Mar 9, 2007 #7

    Astronuc

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    Staff: Mentor

    Yeah, and I think I've already passed my half-life. Fortunately, it's all down hill from now on. :rofl: :rofl:
     
  9. Mar 9, 2007 #8
    you just have to find your re crystalization temperature
     
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