Example 1.4: Point Calculation at Fixed Temperature and Composition
Purpose: Learn to calculate and get detailed phase stability information at a given temperature and composition
Module: PanPhaseDiagram
Thermodynamic Database: Al_Demo.rtdb
Batch file: Example_#1.4.pbfx
From the Al-Mg phase diagram shown in Figure 1.4.1, we know that two phases, AlMg_Beta+Fcc, are stable at the point indicated by Φ (the cross of the two dash lines). Other than that, no detail information about this point can be read directly from this phase diagram. In this example, we perform a Point Calculation to obtain the detail information at the selected point.
Figure 1.4.1: Al-Mg binary phase diagram
Calculation Procedures:
- Load Al_Demo.rtdb following the procedure in Pandat User’s Guide: Load Database, and select Al and Mg two components;
- Perform 0D calculation following the procedure in Pandat User’s Guide: Point Calculation (0D);
- Set Calculation Condition as shown in Figure 1.4.2;
Figure 1.4.2: Point Calculation for an alloy with 30 at% Al and 70 at% of Mg at 300°C
Calculation Method 2 from labeling:
- After the Al-Mg phase diagram is calculated, click
on the Labeling mode, then put the cursor at the selected point and press Ctrl button, click the mouse.
Information obtained from this calculation:
- Two phases, AlMg_Gamma and Hcp, are stable at the given condition (temperature and composition);
- The G, H, S, and Cp of the system at the given composition and temperature are -22744.9 J/mol, 6539.3 J/mol, 51.0935 J/K·mol, and 30.2876 J/K·mol, respectively;
- The equilibrium composition of AlMg_Gamma is x(Al) = 0.409686, x(Mg) = 0.590314;
- The mole fraction of AlMg_Gamma is 0.687999 (weight fraction is 0.696044);
- The G, H, Cp,
, and 
of AlMg_Gamma at equilibrium composition are -23186.3 J/mol, 5976.71 J/mol, 31.3752 J/K·mol, 135.828 J/mol, and 146.6 J/mol, respectively; - The site fraction of AlMg_Gamma are:
= 1, 
= 0.0291951, 
= 0.970805, 
= 0.96088, 
= 0.0391201; - The equilibrium composition of Hcp is x(Al) = 0.058129, x(Mg) = 0.941871;
- The mole fraction of Hcp phase is 0.312001 (weight fraction is 0.303956);
- The G, H, Cp, , and of Hcp at equilibrium composition are -21771.6 J/mol, 7779.87 J/mol, 27.8893 J/K·mol, 179.735 J/mol, and 184.813 J/mol, respectively;
- The site fraction of Hcp is the same as its composition since it is essentially one sublattice model, the second sublattice is occupied by vacancy.
Figure 1.4.3: Calculated results for an alloy with 30 at% Al and 70 at% of Mg at 300°C