Cuiping Guo

Thermodynamic re-assessment of the Ni – Sn system

Abstract The Ni – Sn system was critically re-assessed by means of the CALPHAD technique. The excess Gibbs energies of the solution phases (liquid, fcc (Ni) and bct (Sn)) were modeled with the Redlich–Kister equation. Five intermetallic compounds, Ni3Sn_HT (which is stable at high temperature), Ni3Sn_LT (which is stable at low temperature), Ni3Sn2_HT, Ni3Sn2_LT and Ni3Sn4 in the Ni – Sn system were treated as the formula (Ni,Sn)1/4(Ni,Sn)1/4(Ni)1/2, (Ni,Sn)3/4(Ni,Sn)1/4, (Ni)1/3(Ni,Sn)1/3(Sn)1/3, (Sn)1/5(Ni,Sn)2/5 · (Ni)2/5, and (Ni)1/4(Ni,Sn)1/4(Ni)1/2, respectively. A set of self-consistent thermodynamic parameters of the Ni – Sn system was obtained.

Thermodynamic re-modeling of the Co–Gd system

Abstract The Co–Gd system was re-assessed using the CALPHAD technique. The solution phases (liquid, body-centered cubic, face-centered cubic and hexagonal close-packed) were described by the substitutional solution model. The temperature dependence of the interaction parameters of the liquid phase was separately expressed by the linear function and Kaptay equation. The intermetallic compounds Co17Gd2 and Co5Gd, which have the same CaCu5-type structure, were treated as one phase and described by a three-sublattice model (Co2, Gd)(Co2, Gd)2Co15, with Co2 and Gd mixing on the first and second sublattices and the third sublattice occupied by Co. The other compounds (Co7Gd2, Co3 Gd, Co2Gd, Co3Gd4 and CoGd3) were treated as stoichiometric compounds. Two sets of self-consistent thermodynamic parameters of the Co–Gd system were obtained.

Thermodynamic assessment of the Au-Pr system

The Au–Pr system was critically assessed by means of the CALPHAD technique. The solution phases (liquid, body-centered cubic (Pr), face-centered cubic (Au) and double hexagonal close-packed (Pr)) were modeled with the Redlich–Kister equation. Seven intermetallic compounds, Au6Pr, Au51Pr14, Au36Pr17, Au2Pr, Au4Pr3, AuPr and AuPr2, in the Au–Pr system were treated as stoichiometric compounds. A set of self-consistent thermodynamic parameters of the Au–Pr system was obtained.

Thermodynamic description of the Ce-Mg-Y and Mg-Nd-Y systems

Abstract The thermodynamic modeling and optimization of the Ce-Mg, Ce-Y, Mg-Nd, Nd-Y, Ce-Mg-Y and Mg-Nd-Y systems have been carried out by means of the CALPHAD technique. The solution phases, liquid, body-centered cubic, face-centered cubic, hexagonal close-packed and double hexagonal close-packed, were described by the substitutional solution model. The isostructural MgCe, MgNd and MgY phases with B2 structure form continuous range of solid solutions in the Ce-Mg-Y and Mg-Nd-Y ternary systems. The order-disorder transition between the solutions with A2 structure and compounds with B2 structure in the systems has been taken into account and thermodynamically modeled. The other compounds Mg2Y, Mg24Y5, Mg3R, Mg41R5, Mg2R and Mg12Ce (R = Ce and Nd) in the Mg-R-Y system exhibit different solubilities of the third component. A set of self-consistent thermodynamic descriptions of the Ce-Mg-Y and Mg-Nd-Y systems was obtained.

Thermodynamic description of the Ta–W–Zr system

Abstract The Ta–W, W–Zr and Ta–W–Zr systems are critically reviewed and modeled using the CALPHAD technique. The enthalpy of formation of the stoichiometric compound W2Zr in the W–Zr system is predicted from first-principles calculations. The solution phases (liquid, bcc and hcp) are modeled by the substitutional solution model. The compound W2Zr is treated with the formula (Ta,W)2Zr in the Ta–W–Zr system because of a significant solid solubility of Ta in W2Zr. All experimental data, including the Gibbs energy of formation, enthalpy of formation, activity of Ta and W of bcc phase at 1 200 K, Ta–W and W–Zr phase diagrams, and three isothermal sections of the Ta–W–Zr system at 1 073, 1 098, and 1 873 K, are reproduced in the present work. A set of self-consistent thermodynamic parameters of the Ta–W–Zr system is obtained.

Thermodynamic modeling of the In–Pt–Sb system

Abstract The In–Pt–Sb system is modeled using the CALPHAD technique. The solution phases (liquid, fcc(Pt), rhom(Sb) and tetra(In)) are described as substitutional solution. The enthalpies of formation of the intermetallic compounds, Pt7Sb, Pt3Sb, Pt3Sb2, PtSb, PtSb2 are calculated using first-principles calculations. In the In–Pt–Sb system, the compounds In3Pt2, In2Pt, In7Pt3 in the In–Pt binary system and the compounds PtSb2 and PtSb in the Pt–Sb binary system are treated as line compounds (In,Sb)mPtn according to experimental solid solubility of the third component. The compound In5Pt6 is treated as (In,Pt,Sb)5(In,Pt)6 based on its thermodynamic model in the In–Pt system and experimental solid solubility of Sb in the In–Pt–Sb system. The thermodynamic model of compound InPt3 keeps the order–disorder transition model with fcc(Pt) solid solution which was used in the In–Pt binary system, and is treated as (In,Pt,Sb)0.25(In,Pt,Sb)0.75. Other compounds InPt, In9Pt13, αIn2Pt3, βIn2Pt3, InPt2 and InSb in the In–Pt–Sb system keep the same thermodynamic models as those in binary systems. Based on the published experimental isothermal sections, vertical sections and the liquidus surface projection, the In–Pt–Sb system is modeled, and a set of self-consistent thermodynamic parameters is obtained.

Thermodynamic modeling of the Ba-Mg binary system

Abstract On the basis of the thermochemical and phase equilibrium experimental data, the phase diagram of the Ba–Mg binary system has been assessed by means of the calculation of phase diagrams technique. The liquid phase is of unlimited solubility and modeled as a solution phase using the Redlich–Kister equation. The intermetallic compounds, Mg17Ba2, Mg23Ba6 and Mg2Ba, with no solubility ranges are treated as strict stoichiometric compounds with the formula MgmBan. Two terminal phases, Bcc_Ba and Hcp_Mg, are kept as solution phases, since the solubilities of the two phases are of considerable importance. After optimization, a set of self-consistent thermodynamic parameters has been obtained. The calculated values agree well with the available experimental data.

Thermodynamic modeling of the Ge-La binary system

The Ge-La binary system was critically assessed by means of the calculation of phase diagram (CALPHAD) technique. The associate model was used for the liquid phase containing the constituent species Ge, La, Ge3La5, and Ge1.7La. The terminal solid solution diamond-(Ge) with a small solubility of La was described using the substitutional model, in which the excess Gibbs energy was formulated with the Redlich-Kister equation. The compounds with homogeneity ranges, α(Ge1.7La), β(Ge1.7La), and (GeLa), were modeled using two sublattices as α(Ge,La)1.7La, β(Ge,La)1.7La, and (Ge,La)(Ge,La), respectively. The intermediate phases with no solubility ranges, Ge4La5, Ge3La4, Ge3La5, and GeLa3, were treated as stoichiometric compounds. The three allotropic modifications of La, dhcp-La, fcc-La, and bcc-La, were kept as pure element phases since no solubility of Ge in La was reported. A set of self-consistent thermodynamic parameters of the Ge-La binary system was obtained. The calculation results agree well with the available experimental data from literatures.

A thermodynamic description of the Ce–La–Mg system

Abstract The thermodynamic optimization of the Ce–La and Ce–La–Mg systems has been carried out using the CALPHAD technique. The solution phases (liquid, bcc, fcc, hcp and dhcp) were described with a substitutional solution model. The isostructural compounds MgCe in the Ce–Mg system and MgLa in the La–Mg system with B2 structure form a continuous range of solid solution in the Ce–La–Mg system. The order–disorder transition between the solutions with A2 structure and compounds with B2 structure in the system has been taken into account and thermodynamically modeled. The other isostructural compounds Mg12Ce and Mg12La, Mg17Ce2 and Mg17La2, Mg41Ce5 and Mg41La5, Mg3Ce and Mg3La, and Mg2Ce and Mg2La were described as such formula Mg12(Ce, La), Mg17(Ce, La)2, Mg41(Ce, La)5, Mg3(Ce, La, Mg), Mg2(Ce, La), respectively. A set of self-consistent thermodynamic description of the Ce–La–Mg system was obtained.

Thermodynamic modeling of the Cu–Se system

Abstract The Cu – Se system was modeled by means of the CALPHAD technique. Considering two miscibility gaps of the liquid existed on each side of the compound Cu2Se, the associate model with the associate species “Cu2Se” was adopted to describe the Gibbs energy for the liquid and compared to the random solution model. The optimizing results showed that the thermodynamic model describing the liquid phase as a solution of Cu, Se and a “Cu2Se” associate fits well with the experimental data. The intermetallic compounds, Cu3Se2, α-CuSe, β-CuSe, γ-CuSe and CuSe2 were treated as stoichiometric compounds. The com-pounds α-Cu2Se and β-Cu2Se, which have a homogeneity range, were treated as the formulae α-(Cu, Se)2Se and β-(Cu, Se)2Se by a two-sublattice model. A set of self-consistent thermodynamic parameters of the Cu – Se system was obtained.