I am trying to thermodynamically model the quaternary system for SS304L Considering Fe-Cr-C-Ni configuration. I need to find out the equilibrium condition during solidification process depending upon the chemical potential of involved elements. It is difficult to visualize the combination of 4 ternary systems to yield one quaternary system for the equilibrium conditions. A Tetrahedron can be a key to the solution of this problem but I am unable to do this in "Thermocalc". My questions
1. Has anyone ever drawn a similar quaternary phase diagram?
2. What are the other possible solutions to see the equilibrium conditions of this system depending upon the common tangent to the Gibbs energy curves?
3. Utilizing the experimental CalPhaD database of this system how can I get the 1) equilibrium temperature during monotectic reaction at 0.02% carbon ( L --> L + Delta ferrite ), 2) equlibrium concentrations of Cr, C, and Ni?
Hello,
To answer the first question, you can now make some tetrahedrons using VRML files. (see the TC online help with the keyword "tetrahedron"). But to do so, you will have to fix the temperature.
You can also fix the composition of the metals within the alloy and plot the phases at equilibrium as a function of C amount and T. In 304, approximately :
7 X more Fe than Ni,
2 X more Cr than Ni.
You will obtain a diagram with x axis : Temperature in K and y axis C activity (refered to Graphite). You can predict the equilibria between liquid, alloy (bcc, fcc) and carbides. See Example 1
Under the same condition and fixing the carbon amount (here 0.04% mass.), you can also plot the composition of the ferrite (bcc phase, in mass fraction). See example 2.
Regards
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