Thermodynamics and phase diagram calculation of the binary arsenic-tellurium system in the framework of the generalized lattice model

In this work we describe how to efficiently calculate thermodynamic properties and T-x diagram of binary As-Te solution in the generalized lattice model. All the thermodynamic parameters of the As-Te solution are obtained within framework of the generalized lattice model. The binary phase diagram of As-Te system is calculated and good agreement with experimental data is obtained.

Investigation of the Quasi-Binary Phase Diagram FLiNaK-NdF3

The NdF3 solubility in molten eutectic FLiNaK, which is a conceivable medium for a molten salt reactor (MSR), was determined by the quasi-binary phase diagram FLiNaK-NdF3. The eutectic mixture FLiNaK was prepared by direct melting of components LiF, NaF and KF·HF. The acidic anhydrous salt (KF·HF) was used instead of the hygroscopic KF. The NdF3 was sintered by hydrofluorination of Nd2O3. The oxygen impurity in the prepared eutectic FLiNaK, determined by an oxygen analyzer LECO OH836, was 0.036 wt.%, whereas the NdF3 contained 0.04 wt.% of oxygen. A part of the FLiNaK-NdF3 quasi-binary phase diagram was obtained using two thermal analysis techniques: differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The FLiNaK-NdF3 phase diagram in the region of 0–30 mol.% NdF3 contains one eutectic at 2 mol.% NdF3 and 450 °C and two peritectic points: 8 mol.% NdF3 at 500 °C and 22 mol.% NdF3 at 575 °C. The region of the FLiNaK-NdF3 phase diagram below the liquidus line is rather complicated due to the complex structure of the multicomponent system in its molten state, as in its solid state. The NdF3 solubility in FLiNaK is about 5 mol.% at 490 °C and 29 mol.% at 700 °C; this means that the process of the MA transmutation in the MSR can be carried out in molten FLiNaK with a content of actinides as high as 15–20 mol.% in the temperature range of 550–650 °C.

Systematic Development of Eutectic High Entropy Alloys by Thermodynamic Modeling and Experimentation: An Example of the CoCrFeNi-Mo System

Face centered cubic (FCC) high-entropy alloys (HEA) exhibit excellent ductility while body centered cubic (BCC) HEAs are characterized by high strength. Development of fine two-phase eutectic microstructure (consisting of a tough phase such as fcc and a hard phase such as bcc/intermetallic) can help in obtaining an extraordinary combination of strength and ductility in HEAs. Designing eutectic high entropy alloys is an extremely difficult task for which different empirical and non-empirical methods have been previously tried. In the present study, the possibility of developing a eutectic microstructure by the addition of Mo to CoCrFeNi was evaluated by calculation of the pseudo-binary phase diagram. Experimental results validated the presence of eutectic reaction in the calculated phase diagrams; however, small changes in the calculated phase diagrams were proposed. It has been shown that calculated pseudo-binary phase diagrams can provide a very good starting point for the development of eutectic HEAs and help in exponentially reducing the amount of experimental effort that may be required otherwise. Eutectic mixture consisting of FCC (A2) phase and intermetallic phases (σ and μ) was successfully obtained by the addition of Mo to the CoCrFeNi system. The development of the eutectic microstructure showed a profound effect on the mechanical properties. Hardness of the samples increased from 150 HV for CoCrFeNiMo0.1 to 425.5 HV for CoCrFeNiMo1.0, whereas yield strength increased from around 218 MPa for CoCrFeNiMo0.1 to around 1100 MPa for CoCrFeNiMo1.0.