Thermodynamic Study On The Binary Systems Of Sc-Ⅹ(X=La, Li, Cr) And On The Ternary Systems Of C-Cr-Nb And Co-Cr-W

The CALPHAD (CALculation of PHAse Diagram) method is the most effective way to obtain the multi-component phase diagrams. In persent works, the CALPHAD method was used to study the thermodynamic properties and phase diagram of the Sc-La, Sc-Li and Sc-Cr binary systems in the Al alloy systems and of the C-Cr-Nb and Co-Cr-W ternary systems in the cemented carbides systems. The results of the present work are summarized as follow:(1) Based on the critical assessment of the experimental data in the literature for the Sc-La, Sc-Li and Sc-Cr binary systems, the thermodynamic models for the individual phases were established and the thermodynamic optimization of the three systems were performed. The experimental Sc-X (X=La, Li, Cr) phase diagrams can well be produced with the presently obtained thermodynamic parameters. Furthermore, the extrapolated Al-Sc-X ternary diagrams with the thermodynamic parameters of the related binary systems can throw light on understanding the alloying behaviors and the microstructures’influence of the additive elements such as Sc etc in the Al alloys. The obtained thermodynamic parameters for the binary systems are incoporated in the thermodynamic database of the Al alloys in our group.(2) The thermodynamic modeling of an important ternary system C-Cr-Nb in the cemented carbides system of C-W-Co-Ti-Ta-Nb-N-Cr was carried out in the present work. Based on the critical evaluation of the experimantal data in the literature, the thermodynamic optimization of the C-Cr, C-Nb and Cr-Nb binary systems was conducted. Taking into account the expermental information on the two isothermal sections at1050℃and1350℃, on the three vertical sections at Cr0.79C-Cr0.79Nb and CrC0.07-NbC0.07and NbC0.9-Cr98Nb2, and on the liquid surface projection, the thermodynamic optimization of the C-Cr-Nb system was performed and a set of self-consisten parameters for the C-Cr-Nb system was obtained. The calculated phase diagram can well reproduce the experiment phase diagram.(3) With the parameters of the boundary binary systems in the database of the cemented carbides system of our research group, the thermodynamic parameters of the Co-Cr-W ternary system were re-optimized. The obtained parameters in this work can well describe the Co-Cr-W ternary system, and have a good compatibility with the thermodynamics database of our research group.