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Homework Help: Phase diagram of Ag - Cu question

  1. Jun 25, 2009 #1
    1. The problem statement, all variables and given/known data
    Describe equilibrium cooling from 1200 C to 200 C of an alloy containing 40 wt% Ag. Draw the schematic equilibrium cooling curve

    3. The attempt at a solution

    Alloy begins as a liquid, begins to solidify as temperature reaches the liquidus line; alpha accumulates and the liquid slides down the liquidus line and the composition of alpha slides down the solidus line until they both reach the eutectic tie line where the last liquid has to solidify, the alpha is already solid but the liquid is coming toward the eutectic point and it has to solidify there. The liquid transforms into some alpha and some beta and there is a thermal arrest until it all solidifies..............

    now, I don't know exactly what happens. To be more specific, I am wondering exactly how that cooling curve would look because I'm confused as to how the phases travel around the phase diagram given a specific composition and being cooled.... Starting with the liquid alloy, as it cools, I know that the equilibrium alpha + Liquid two phase field can be considered "empty" - meaning nothing is in there (at least that's what my prof. said), so does the liquid actually travel down the liquidus line, hit the eutectic point of equilibrium, the travel back to the left (in the Ag - Cu phase diagram case) along the eutectic tie line, until it regains its original 40-60 composition? Because at the eutectic point, the composition is predetermined..... :confused:
  2. jcsd
  3. Jul 1, 2009 #2
    Hi. I found help for the cooling curve at this web-site:


    About midway down, there is a graph with the cooling curve. For our binary eutectic problem, I believe all of the cooling curves would look like what is on that web-page. Would you happen to be taking ME 311 right now at UT. We have that same question for hw.
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