Isopleth of Al-Mg-Zn at 15 at% Zn

Purpose: Learn to calculate and use an isoplethal section in a ternary system

Module: PanPhaseDiagram

Thermodynamic Database: AlMgZn.tdb

Batch file: Example_#1.6.pbfx

As mentioned in Isotherm of Al-Mg-Zn at 500°C, isopleths are sections vertical to the triangle base plane of the triangular prism. An isopleth is important in understanding phase relationship in a ternary system when temperature is a variable. In this example, we will calculate an isoplethal section in the Al-Mg-Zn ternary parallel to Al-Mg binary with 15 at% of Zn.

Calculation Procedures:

Load AlMgZn.tdb following the procedure in Pandat User's Guide: Load Database , and select all three components;
Perform 2D calculation following the procedure in Pandat User's Guide: Section Calculation (2D) ;
Set Calculation Condition as shown in Figure 1;

Figure 1: 2D calculation of an isopleth parallel to Al-Mg binary with 15 at% Zn

Post Calculation Operation:

Label phase field following the procedure in Pandat User's Guide: Icons for Graph on Toolbar;
Change graph appearance following the procedure in Pandat User's Guide: Property;

Figure 2: Calculated isopleth parallel to Al-Mg binary with 15 at% Zn

Information obtained from this calculation:

Phase stability as a function of composition of Mg and temperature. Single phase, two-phase, and three-phase regions, can be viewed clearly at different composition and temperature;
Tie-lines cannot be viewed on an isopleth since they are usually not on the same isoplethal plane except for a pseudo-binary. The tieline information is listed in tieline Table as shown in Figure 3.
The invariant reactions and the phase composition for every phase in the invariant reaction are listed in invariant_tieline table as shown in Figure 4.

Figure 3: The tieline table showing the detailed information of calculated tieline

Figure 4: The invariant_tieline table showing composition of each phase involved in the invariant reaction