Hume-Rothery Symposium: Thermodynamics, Phase Equilibria and Kinetics for Materials Design and Engineering: CALPHAD Thermodynamic and Diffusion Database Development
Sponsored by: TMS Structural Materials Division, TMS: Alloy Phases Committee, TMS: Integrated Computational Materials Engineering Committee
Program Organizers: Carelyn Campbell, National Institute of Standards and Technology; Michael Gao, National Energy Technology Laboratory; Wei Xiong, University of Pittsburgh
Wednesday 2:00 PM
February 26, 2020
Room: 32A
Location: San Diego Convention Ctr
Session Chair: Wei Xiong, University of Pittsburgh; Qing Chen, Thermo-Calc Software AB
2:00 PM Invited
Developing CALPHAD Databases for Thermophysical Properties of Metals and Alloys: Hailin Chen1; Masoomeh Ghasemi1; Qing Chen1; 1Thermo-Calc Software AB
Calphad method has proved extremely useful in providing fundamental phase diagram information for industrial relevant multicomponent systems in a computational way. Its success relies on the simple and efficient scheme it adopted to model the Gibbs energy of each phase hierarchically from low-order systems to high-order ones, and evaluate model parameters by considering both experimental observations and ab initio calculation data. The method later found its way for describing multicomponent diffusivities so that the diffusion controlled phase transformations can be simulated in a multicomponent alloy. Other thermophysical properties, such as volume or density, can also be modeled in a similar fashion. In this talk, we present our recent progress in constructing Calphad models and developing databases for electric resistivity, thermal conductivity and viscosity of metals and alloys. Verification and validation results will be shown and discussed.
2:40 PM Invited
Development of a Comprehensive Diffusion (mobility) Database for Lightweight Magnesium Alloys: Wei Zhong1; Ji-Cheng Zhao1; 1University of Maryland
Diffusion coefficients are essential data for kinetic simulations of materials processes and properties. A systematic study was performed to collect both impurity (dilute) diffusion coefficients and interdiffusion coefficients of several key alloying elements of lightweight Mg alloys. High-throughput diffusion multiples and novel liquid-solid diffusion couples are combined with a forward-simulation analysis to extract a large amount of diffusion coefficients of Al, Ca, Ce, Gd, Li, Mn, Sn, Y and Zn in Mg. A comprehensive and reliable diffusion coefficient (mobility) database for Mg-based systems is established by integrating the experimental measurements on these 9 elements with first-principles calculation results as well as limited measurements on other elements. The comprehensive mobility database covering more than 20 elements will contribute to the accelerated development of next-generation Mg alloys.
3:20 PM Invited
Thermodynamic Assessment of the Fe-B and Fe-B-C- Systems: Katsunari Oikawa1; Nobufumi Ueshima1; 1Tohoku University
Born is added to improve the mechanical strength through enhancement hardenability by segregation to grain boundary. While, boron forms the borocabide as well as boride in the steels. These precipitates have harmful effect on the mechanical properties. To understand the behavior of boron and carbon in the steel, phase diagrams of Fe-B-C system are essential information.In this study, the phase equilibrium of the Fe-B and Fe-B-C systems were investigated using diffusion couple method and DSC. Furthermore, thermodynamic assessment of these systems was carried out by using the CALPHAD method. In the Fe-B-C system, the solubility of carbon in liquid and fcc phases was decreased with increasing boron content. The assessment also predicted the metastable two-liquid phase separation in Fe-Fe2B region. This phase separation might be the origin of two-phase separation of the Fe-B base amorphous. These results are very useful to understand the effects of boron on the steel.
4:00 PM Break
4:20 PM Invited
CALPHAD Databases for Co-based Alloys: Peisheng Wang1; Ursula Kattner2; Carelyn Campbell2; Gregory Olson1; 1Northwestern University; 2National Institute for Standards and Technology
Efforts to establish a reliable multi-component, multi-phase thermodynamic database (CALPHAD) for the design of Co-based superalloys continue to progress in the present work. The major objectives for the refinement of the present database are to develop a quantitative description of the metastable L12 phase and to enable reliable prediction of the homogeneity ranges of the TCP phases. A method to describe the magnetic contribution to the total energy for the TCP has been developed. In addition, a molar volume database has been developed in the present work. Several new Co-based superalloys have been designed using the current thermodynamic database by coupling it with the diffusion mobility and molar volume databases. Other properties, such as creep resistance and oxidation resistance, of these alloys will also be discussed.
5:00 PM Invited
Diffusion Mobilities in Co-Ni-Al-Cr System: Kil-Won Moon1; Carelyn Campbell1; 1National Institute of Standards and Technology
As a part of on-going effort to develop CALPHAD-based thermodynamic and diffusion databases for Co-based alloys, currently available diffusion mobility descriptions and experimental diffusion couple data are used to assess the mobility parameters of the FCC phase in Co-Ni-Al-Cr system at 1000 ºC and 1200 ºC. The current work optimizes the mobilities parameters by direct comparison with experimental profiles instead of derived diffusion coefficients from the experimental profiles. This method is particularly useful for using multicomponent diffusion couple data, where it is often difficult to obtain accurate diffusion coefficients that require the crossing of multiple diffusion paths. Efficient optimization of the mobility parameters using the experimental profiles directly does require a data smoothing process and defining a common Matano interface for the experimental and computed profiles. These processes are demonstrated within the optimization of the Co-Ni-Al-Cr system. The results of the optimized mobility parameters are presented.