Zhanmin Cao

Thermodynamic Assessment of the Ni-Sb Binary System

The Ni-Sb binary alloy system was thermodynamically assessed using CALPHAD approach in this article. Excess Gibbs energies of solution phases, liquid and fcc phases, were formulated using the Redlich-Kister expression. The intermediate phases were modeled by the sublattice model with (Ni, Va)0.5(Ni, Sb)0.25(Ni)0.25 for Ni3SbHT phase and (Ni, Va)0.3333(Sb)0.3333(Ni, Va)0.3333 for NiSb phase. The other phases including Ni3Sb, Ni7Sb3, and NiSb2 were treated as stoichiometric compound owing to their narrow composition ranges. Based on the reported thermodynamic properties and phase diagram data, the thermodynamic parameters of these phases were optimized, and the obtained values can reproduce the available experimental data well.

Formation Mechanism of CaO-SiO2-Al2O3-(MgO) Inclusions in Si-Mn-Killed Steel with Limited Aluminum Content During the Low Basicity Slag Refining

Pilot trails were carried out to study the formation mechanism of CaO-SiO2-Al2O3-(MgO) inclusions in tire cord steel. 48 samples were taken from 8 heats of liquid steel during secondary refining, which were subsequently examined by an automatic scanning electron microscope with energy dispersive spectrometer (SEM–EDS). Characteristics of thousands of oxide inclusions at different refining stages were obtained, including their compositions, sizes, morphologies, etc. Based on the obtained information of inclusions, details during formation of CaO-SiO2-Al2O3-(MgO) inclusions were revealed and a new mechanism was proposed, including their origin, formation, and evolution during the refining process. It was found that CaO-SiO2-Al2O3-(MgO) inclusions were initially originated from the CaO-SiO2-MnO-(MgO) inclusions, which were formed during BOF tapping by the coalescence between MnO-SiO2 deoxidation products and the emulsified slag particles because of violent flow of steel. This can be well confirmed by the evaluation of the formation thermodynamics of CaO-SiO2-MnO-(MgO) inclusions, which was proved very difficult to be produced by intrinsic reactions inside liquid steel. Because of chemical reactions between CaO-SiO2-MnO-(MgO) inclusions and molten steel, they were mainly changed into CaO-SiO2-MnO-Al2O3-(MgO) and partially into CaO-SiO2-Al2O3-(MgO), which may be detrimental to the cold drawing ability of coils. Based on this finding, improvements were made in industrial production during BOF tapping and secondary refining. The results indicated that such (CaO-SiO2)-based inclusions existed in conventional process were effectively decreased after the improvements.

Critical Evaluation and Thermodynamic Optimization of the Ti-C-O System and Its Applications to Carbothermic TiO2 Reduction Process

Based on the critical evaluation of available phase diagram, thermodynamic, and crystal structure data, the ternary Ti-C-O system is thermodynamically assessed using the Calculation of Phase Diagram method. Both binary Ti-C and Ti-O systems are reassessed to obtain the successful description of ternary Ti-C-O system for the first time. The liquid phase is described by the modified quasichemical model, which takes short-range ordering in liquid solution into account. All solid solutions are described using compound energy formalism. In particular, a completed solid solution between TiCx and TiOy with the excess solubilities of Ti, C, and O is accurately described with the (Ti, Va)1(C, O, Va)1 solution structure. The thermodynamic models with a set of optimized self-consistent model parameters can reproduce available reliable experimental data within experimental error limits. The results are also applied to the thermodynamic analysis of complex carbothermic TiO2 reduction process.

Prediction of Surface and Interfacial Tension Based on Thermodynamic Data and CALPHAD Approach

In this article, following a brief introduction concerning experimental measurements of surface and interfacial tensions, methods for calculating surface tension and surface segregation for binary, ternary, and multicomponent high-temperature melts based on Bulters original treatment [1] and on available physical properties and thermodynamic data, especially excess Gibbs free energies of bulk phase and surface phase versus temperature obtained from thermodynamic databases using the calculation of phase diagram (CALPHAD) approach, with special attention to the model parameter, have been described. In addition, the geometric models can be extended to predict surface tensions of multicom-ponent systems from those of sub-binary systems. For illustration, some calculated examples, including Pb-free soldering systems and phase-diagram evaluation of binary alloys in nanoparticle systems are given. On the basis of surface tensions of high-temperature melts, interfacial tensions between liquid alloy and molten slag as well as molten slag and molten matter can be calculated using the Girifalco-Good equation [2]. Modifications are suggested in the Nishizawas model [3] for estimation of interfacial tension in liquid metal (A)/ceramics (MX) systems so that the calculations can be carried out based on the sublattice model and thermodynamic data, without deliberately differentiating the phase of MX at high temperature. Finally, the derivation of an approximate expression for predicting interfacial tension between the high-temperature multi- component melts, employing Beckers model [4] in conjunction with Bulters equation and interfacial tension data of the simple systems is described, and some examples concerning pyrometallurgical systems are given for better understanding.

Thermodynamic reassessment of Ni–Ga binary system

New experimental measurements of the phase diagram and the mixing enthalpy of liquid phase along with the previous experimental data were used in a reassessment of the Ni–Ga system. A set of self-consistent thermodynamic parameters of the Ni–Ga system is obtained using the calculation of phase diagram (CALPHAD) technique, and the available phase diagram and thermodynamic data are reproduced well within experimental error limits. Some noticeable improvements are obtained in the present work compared with the previous assessment: (1) the calculated Ga-rich liquidus is more reasonable; (2) Ni3Ga7 is adopted as the most Ga-rich compound rather than NiGa4; (3) the Ni5Ga3 phase is treated as the nonstoichiometric compound with consideration of its narrow homogeneity range; (4) the phase transformation between B81.5_Ni3Ga2 and Ni13Ga9 is considered instead of treating them as Ni3Ga2 phase simply; (5) the latest experimental data of mixing enthalpy for the liquid phase are adopted. The present study can be used as a basis for the development of a thermodynamic database of the Ni-based semiconductor alloy systems.

Correction to: Thermodynamic Assessment of the In-Ni-Sb System and Predictions for Thermally Stable Contacts to InSb

In the original article, there are three errors in the parameters listed under ω(NiIn): (Ni, Va)0.5(In, Ni)0.5 in Table␣II.