# New Content on Slags and Oxide Materials on Thermo-Calc Software’s Learning Hub

Is the CaO-Al2O3 phase diagram a true binary? It certainly looks like a binary system, but is it not a section through the ternary Ca-Al-O system? This is one of several fundamental questions on calculations of oxide systems that is covered in over two hours of fresh content on calculations of oxide systems using the TCOX database that is now available in the Learning Hub. The Learning Hub is our digital on-demand self-paced learning platform.

Fig 1. CaO-Al phase diagram.

## Examples Covered in the New Learning Hub Content

Oxygen Isobars and Stability Diagrams

Oxygen isobars are very important to understand how a material will behave as a function of oxygen partial pressure and temperature, as shown in the left plot of Figure 2. Additionally, they are important in understanding how to calculate and interpret phase diagrams with activities instead of compositions as axes (sometimes called stability diagrams), as shown in the right plot in Figure 2. In the new videos in the section “Fe-O System: Basics” we walk through how to set up the calculations to obtain exactly the plots below. We discuss the basic concepts and explain how to interpret the results.

Fig 2. Phase diagram of the Fe-O system with oxygen isobars included as dotted lines (left) and the corresponding stability diagram (right).

Effect of Oxygen Partial Pressure on Phase Relations

The system Fe-Mg-O is a good example showing that the oxygen partial pressure can have a profound influence on the phase diagram. At low oxygen partial pressures, iron is predominantly Fe2+ and the halite phase forms a complete solid solution from MgO to FeO, as shown in the left plot in Figure 3. Alternatively, in air, iron is mixed Fe2+/Fe3+ and, in addition to the halite phase (Fe,Mg)O, the spinel (Fe,Mg)3O4 and corundum (Fe,Mg)2O3 phases are also observed, as shown in the right plot in Figure 3. The new videos on the Learning Hub discuss how these types of calculations are done in Thermo-Calc and further discuss the results.

Fig 3. MgO-FeOx phase diagram calculated in air (left) and at low oxygen partial pressure (right).

Miscibility Gaps

Oxide systems often contain miscibility gaps. The reason can be traced to the strong tendency of forming short range ordering in the liquid. The miscibility gaps can be stable or metastable. The metastable miscibility gap in the Al2O3 – SiO2 system, for example, is important for certain types of glass ceramics. In the new videos, tips and tricks are given on how to avoid problems when calculating such miscibility gaps.

Fig 4. Stable liquid miscibility gap in the CaO-SiO2 system (left) and metastable miscibility gap in the supercooled liquid in the Al2O3-SiO2 system (right).

This set of 14 videos about oxides and slags focus on fundamental aspects of calculations of oxide systems using the TCOX database. We are planning to add additional videos on oxides and slags in the near future that focus on more applied topics such as:

• Steel-slag interaction
• Heat balance calculations
• Reduction of iron ore with natural gas, coke, and H2
• Kinetic process simulations of primary and secondary steel making
• High temperature corrosion/oxidation
• And more!

## See the Full Content on the Learning Hub

You can browse all of the videos available in the Thermo-Calc course, including these new videos on Slags and Oxide Materials, which are at the bottom of the page. The Thermo-Calc course includes a few sample lessons, which are available without a subscription to the Learning Hub.

To access the full learning material on oxides, you can get a Learning Hub subscription, which gives you full streaming access for one year to all of the courses for the graphical mode of Thermo-Calc, Diffusion Module (DICTRA), and Precipitation Module (TC-PRISMA), as well as the TC-Python API. New content is added regularly.

You also get access to the regularly hosted office hours – A live virtual group meeting where you can ask questions related to the course, or how to apply the lessons to your own problems.