Activity Contour Diagram

Purpose: Learn to calculate activity contour diagram. In this example, the activity contour lines of Mg will be calculated and plotted on the isothermal section of the Al-Mg-Zn ternary system at 500 °C.

Module: PanPhaseDiagram

Thermodynamic Database: AlMgZn.tdb

Batch file: Example_#1.15.pbfx

Calculation Procedures:

• Load AlMgZn.tdb following the procedure in Pandat User's Guide: Load Database , and select all three components;

• First set up the calculation condition as shown in Figure 1 in the same way as we did to calculate Al-Mg-Zn isotherm (see Isotherm of Al-Mg-Zn at 500°C), then click “Contour Lines” to open the contour line dialog as shown in Figure 2;



Figure 1:  Setup calculation for an isotherm in the Al-Mg-Zn ternary at 500°C, then press “Contour Lines”

• Choose “User Custom Type” and click AddType in “a(Mg:Hcp)” for the Contour Type in the “Properties” window as shown in Figure 2, then press OK;

  

  Figure 2:  Type in “a(Mg:Hcp)” for the Contour Type in the “Properties” window, it is to calculate the activity of Mg contour lines using Hcp Mg as reference state

Post Calculation Operation:

• Change graph appearance following the procedure in Pandat User's Guide: Property;

• Label each line by putting the cursor on each line and wait for the tool tip to pop out, then press F2;

Information obtained from this calculation:

• Figure 3 shows the activity contour diagram of Mg at 500 °C. The variation of Mg activity in the composition triangle is clearly seen at this temperature;

• Activity contour lines can also be plotted only in the selected phase field, such as in the Liquid phase field, in the Liquid+Fcc phase field. An example is given in Pandat User's Guide: Activity Contour Diagram ;