Calculation of Activity at Constant Temperature
Purpose: Learn to calculate activities of components in a system
Module: PanPhaseDiagram
Thermodynamic Database: AlMgZn.tdb
Batch file: Example_#1.10.pbfx
Figure 1 is the Al-Mg binary phase diagram. In this example, we learn to calculate the activity of Al and Mg as a function of composition, x(Mg), at 300°C (the red dash line).
Calculation Method 1, From menu bar “Property”:
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Load AlMgZn.tdb following the procedure in Pandat User's Guide: Load Database , and select Al and Mg two components;
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Click “Property” on the menu bar and select “Thermodynamic Property”;
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Set Calculation Condition as shown in Figure 2. The property selected is a(*), and the reference states are set as Fcc for Al and Hcp for Mg; (*) means the activity of every component (both Al and Mg in this case);
Calculation Method 2, From menu bar “PanPhaseDiagram”:
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Load AlMgZn.tdb following the procedure in Pandat User's Guide: Load Database, and select Al and Mg two components;
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Click “PanPhaseDiagram” on the menu bar and select “Line Calculation”;
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Add the new table following the procedure in Pandat User's Guide: Icons for Table on Toolbar ;;
Post Calculation Operation:
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Change graph appearance following the procedure in Pandat User's Guide: Property;
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Add text and arrow on the plot following the procedure in Pandat User's Guide: Icons for Graph on Toolbar;
Information obtained from this calculation:
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Figure 3 shows the activities of Al and Mg as a function of x(Mg) using Fcc Al and Hcp Mg as reference states;
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Activity of Al is 1 at x(Al)=1 (x(Mg)=0) since it is pure Fcc Al at this temperature and Fcc is used as the reference state; Activity of Al decreases with the increase x(Mg) and becomes zero at x(Mg)=1;
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Activity of Mg is 0 at x(Al)=1 (x(Mg)=0) and increases with the increase x(Mg) and becomes 1 at x(Mg)=1;
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Activity of either component is constant in a two-phase field.
