Nowadays, most steel grades are well described by commercial databases enabling to perform reliable calculations of thermodynamic properties and phase diagrams over a wide composition range. However, to further improve thermodynamic databases for advanced steels, e.g., silicon alloyed electrical steels, medium Mn-steels, or higher alloyed tool steels, there is still a need to provide new phase equilibrium data obtained by modern laboratory techniques.
This work presents an overview of the experimental procedure at the Chair of Ferrous Metallurgy at Montanuniversitaet Leoben. Taking the example of the selected systems, the workflow will be demonstrated. Investigations started with melting high-purity alloys by induction melting and subsequent centrifugal spin casting. Phase transitions of the alloys were systematically determined up to the liquidus temperature using the well-established differential thermal analysis (DTA) and differential scanning calorimetry (DSC) method. Since manganese shows strong evaporation tendency during melting leading to a possible damage of the DSC measuring devices, a micro-DTA-protected setup with closed crucible by tantalum lids is applied. Using these methods, all high-temperature phase transformations of peritectic, eutectic and eutectoid steel systems can be measured under equilibrium conditions. The measured phase equilibrium data are typically used to develop advanced thermodynamic databases for steel in the CALPHAD framework.