The 260 °C phase equilibria of the Sn–Sb–Ag ternary system and interfacial reactions at the Sn–Sb/Ag joints

The isothermal section of the Sn–Sb–Ag ternary system at 260 °C has been determined in this study by experimental examination. Experimental results show no existence of ternary compounds in the Sn–Sb–Ag system. Two extensive regions of mutual solubility have been determined. The one located between the two binary isomorphous phases, Ag₃Sn and Ag₃Sb, is labeled as and the other one located between the two binary isomorphous phases, Ag₄Sn and Ag₄Sb, is labeled as ξ. The phase is a very stable phase and is in equilibrium with ξ, Sb, SbSn, Sb₂Sn₃, and liquid Sn phases. Each of the Sb and SbSn phases has a limited solubility of Ag. Only one stoichiometric compound, Sb₂Sn₃, exists. Besides phase equilibria determination, the interfacial reactions between the Sn–Sb alloys and the Ag substrate were investigated at 260 °C. It was found that the phase formations in the Sn–Sb/Ag couples are very similar to those in the Sn/Ag couples.     

Thermodynamic assessment of the Ga–Sc and Ga–Tb systems

The Ga–Sc and Ga–Tb binary systems have been assessed with CALPHAD method. Liquid is treated as substitutional solution phase, of which the excess Gibbs energies are modeled by Redlich–Kister polynomial function. The binary intermetallic compounds are treated as stoichiometric phases. Thermodynamic parameters of various phases have been optimized and the calculated results are in reasonable agreement with experimental data.     

Experimental investigation and thermodynamic description of the In–Sb–Sn ternary system

Phase equilibria in the In–Sb–Sn ternary system have been studied experimentally and calculated by the CALPHAD method. Solubility of indium in the SbSn phase was experimentally established. Our own SEM–EDX results were used together with the literature data for thermodynamic modeling of the Gibbs energy of the SbSn intermediate phase. Optimized phase diagrams of the isothermal sections at 100 °C and 300 °C were compared with the experimental results from this work and literature. Three calculated vertical sections were compared with the DTA results from this work and with available thermal analysis data reported in the literature. Some calculated thermodynamic functions are compared with experimental values reported in the literature. Reasonable agreement between calculations and experimental data was observed in all cases.     

Phase equilibria of the cu-in system II: Thermodynamic assessment and calculation of phase diagram

The phases in the Cu-In binary were modelled thermodynamically using the Redlich-Kister expression for the Gibbs energies of the solution phases, the Wagner-Schottky model for those of the η (η)’)-Cu₂ln phase (taking η and η)’ to be a single phase), and assuming line compound behavior for the other intermetallic phases. The model parameters were obtained using primarily the thermodynamic data, as well as the phase equilibrium data. The thermodynamic values for the various phases calculated from the models are in reasonable agreement with the experimentally determined thermodynamic data that are available in the literature. The entropies of melting for the intermetallic phases obtained from the models are in accord with the values calculated from the empirical formulas suggested by Kubaschewski. The calculated phase diagram is also in reasonable agreement with the experimentally determined diagram, with the calculated temperatures for all the invariant equilibria within 1°C of the experimental values. The discrepancies between the calculated and experimental phase boundaries at the invariant temperatures are less than 1 at.% except those involving βCu₄Inn and γCu₇ln₃. These two phases were taken to be line compounds in the present study, although experimentally they exist over appreciable ranges of homogeneity. Current address: Dept. of Chemical Engineering, National Tsing Hua University, Taiwan.     

Thermodynamic modeling of the CeO2–CoO phase diagram

A thermodynamic modeling of the CeO₂–CoO phase diagram was performed with recent experimental data. The excess Gibbs energies of the solution phases were described on the basis of the simple regular solution. A consistent set of optimized interaction parameters was derived for describing the Gibbs energy of each phase in this system leading to a good fit between calculation and experimental data. The liquidus, solidus, and solvus curves were calculated and also the lattice stabilities of the components were evaluated.     

Determination of the group and phase velocities from time–frequency representation of Wigner–Ville

The experimental measurement of the group and phase velocities of some circumferential waves propagating around a thin elastic tube is a still complex operation. In this study, we show that the dispersion velocity can be determined from a time–frequency representation. We use the Wigner–Ville method by virtue of its interesting properties. On some time–frequency images, the symmetric (S0) and antisymmetric (A1) circumferential waves are identified. The group velocity dispersion estimated from these images is compared with that computed by the proper mode theory method. A good agreement is obtained. The phase velocity is also determined from the group velocity.     

Thermodynamic assessment of the Mo–Re binary system

The existing Mo–Re phase diagrams are reviewed and a thermodynamic calculation of the Mo–Re binary system is undertaken. The Gibbs energies are estimated for liquid, bcc (Mo), hcp (Re), σ and χ phases. The liquid, bcc (Mo) and hcp (Re) phases are described by a regular solution model, whereas the σ and χ phases are described respectively by three-sublattice models. For the σ phase, two thermodynamic models are used for calculations and the results are compared. The models take into account the crystallographic structure and similarity between the σ and χ phases. The calculated results remove the ambiguity of the existing phase diagram data and are compared with the experimental data in the literature.     

Formation and some properties of Fe core–shell powders with experimental parameters of the chemical vapor condensation process

Core–shell powders, recently, have aroused interest because of their potential applications in various areas such as electronics, optics, catalysis, ferrofluids, and magnetic data storage. Their unique properties and superior performances are determined by their powder size, shell thickness and surface structure, phase and powder interaction. In this study, carbon-coated Fe core–shell powders were prepared by chemical vapor condensation (CVC) process using Fe metal–organic (Fe(CO)₅) precursor and carbon containing carrier gases such as carbon monoxide and methane. Effects of experimental parameters on the properties of the as-produced core–shell powders were studied by X-ray diffractometer, Brunauer–Emitter–Teller analyzer, high resolution transmission electron microscope and X-ray photoelectron spectrometer. The microstructures and phases of the synthesized core–shell powders varied with the decomposition temperature of the precursors and the flow rate of the carrier gases. CVC Fe powders showed intricate long stand-like structure because of intrinsic magnetic properties of Fe.     

Thermoelectric characteristics and tensile properties of Sn–9Zn–xAg lead-free solders

This study investigates the structural characteristics and tensile properties of the Sn–9Zn–xAg alloy under an electrical current test and oil bath treatment. Experimental results indicate that alternating current (ac) and direct current (dc) led to different values for the fusing electrical current value. Electromigration of direct current (dc) reduced the fusing electrical resistance. In addition, the electrical conductivity of the Sn–9Zn–xAg alloys deteriorated significantly by adding more 2 wt.% Ag. The Sn–9Zn–1Ag specimen underwent no transformation during oil–silicon heat-treatment, however its structure experienced electromigration under electrical current testing. After electrical current testing, the needle-like Zn-rich phases had decomposed, the Ag–Zn compounds had grown, the amount of Sn–Zn eutectic phases had increased, and the content of Sn-rich phase had decreased. Also, prolonging the duration of thermoelectric testing led to a deterioration in the tensile mechanical properties of the specimens. Raising the heat-treatment temperature enhanced the solid solution effect and raised the tensile strength of the as-cast specimens.     

Phase stability,oxidation, and interdiffusion of a novel Ni−Cr−Al−Ti−Si bond-coating alloy between 900 and 1100°C

A novel, low-expansion experimental Ni–Cr–Al–Ti–Si bond-coating alloy was investigated in the as-cast state concerning its phase stability, oxidation resistance in air, and interdiffusion with single-crystal IN-100 at 900, 1000, and 1100°C. Isothermal oxidative thermogravimetry was employed up to 500 hr. Interdiffusion was compared to a commercial Ni–Co–Cr–Al–Y alloy on IN-100. Oxidized Ni–Cr–Al–Ti–Si specimens and diffusion couples were characterized by metallography, SEM, EDX, XRD, and XRF. The Ni–Cr–Al–Ti–Si alloy provides good oxidation resistance in air at least up to 1000°C. The alloy is an alumina former. Due to its coarse microstructure, other oxides (e.g., rutile) may form and considerably dominate the oxidation behavior. The kinetics of oxidation were correlated with temperature, formation of phases, and morphology of oxides. Interdiffusion fluxes between Ni–Cr–Al–Ti–Si and IN-100 were mainly directed to the superalloy. They were faster than in Ni–Co–Cr–Al–Y/IN-100 diffusion couples.     

Oxidation of a Three-Phase Cu–45Ni–30Cr Alloy at 700–800°C Under 1 atm O2

The oxidation of a ternary Cu–Ni–Cr alloy containing approximately 45 wt.% Ni and 30 wt.% Cr has been studied in 1 atm O₂ at 700–800°C. The alloy contains a mixture of three phases: the one with the largest copper and lowest chromium content forms the matrix, the one with an intermediate chromium content has a rather large volume fraction and forms large islands, while the phase richest in chromium forms isolated particles dispersed in the other two phases. At variance with another Cu–Ni–Cr ternary three-phase alloy containing only 20 wt.% Cr and 20 wt.% Ni, which formed complex scales containing mixtures of the oxides of the various components and double oxides, plus an irregular region composed of a mixture of alloy and oxides, the present alloy is able to form protective, external chromia scales. A similar result could be obtained with alloys containing about 20 wt.% Cr, but composed of either a single phase (Cu–60Ni–20Cr) or of a mixture of two phases (Cu–40Ni–20Cr). The need for a larger chromium content for producing chromia scales for three-phase as compared to two-phase Cu–Ni–Cr alloys is attributed to the limitations of the diffusion of the alloy components in the metal substrate imposed by their multiphase nature.     

Phase stability and fcc/hcp martensitic transformation in Fe–Mn–Si alloys: Part II. Thermodynamic modelling of the driving forces and the MS and AS temperatures

This paper presents the second part of a study of the fcc/hcp relative phase stability and the fcc↔hcp martensitic transformation (MT) in the Fe–Mn–Si system. In part I, an experimental database was built up using dilatometric measurements, which covers the composition range in which the fcc↔hcp MT is detected. This new information is analysed in the present work using models for the molar Gibbs energy (G_m) of the various phases. Hcp is a metastable phase in the system, but we show that its properties can be inferred from selected pieces of experimental data, using the concept of T₀ temperature. The assessed G_m functions of the ternary fcc and hcp phases are used to evaluate the so-called resistance-to-start-the-transformation energy (RSTE). According to our results the RSTE in this system vary smoothly with composition, and we account phenomenologically for that using low-order polynomials in the atomic fractions. Finally, the optimum G_m and RSTE functions are also used to calculate the M_S and A_S temperatures for arbitrary compositions in the ternary system. The extensive comparisons between calculations and measurements presented in this work show a very good agreement, which adds to the credibility of the present approach.     

Thermodynamic analysis of alloys Ti–Al, Ti–V, Al–V and Ti–Al–V

Thermodynamic analysis of three binary Ti-based alloys: Ti–Al, Ti–V, and Al–V, as well as ternary alloy Ti–Al–V, is shown in this paper. Thermodynamic analysis involved thermodynamic determination of activities, coefficient of activities, partial and integral values for enthalpies and Gibbs energies of mixing and excess energies at four different temperatures: 2000, 2073, 2200 and 2273 K, as well as calculated phase diagrams for the investigated binary and ternary systems. The FactSage is used for all thermodynamic calculations.     

A model for the prediction of lattice parameters of iron–carbon austenite and martensite

Prediction of lattice parameters of interstitial iron–carbon austenites and martensites as a function of carbon concentration and temperature are given. The model is based on the two assumptions that the change in lattice parameters of the pure Fe phase is due to the occupation by carbon atoms to the octahedral holes in the fcc austenite and the bct martensite; and on the relative change in length and vacancy concentration at the lattice sites that are in thermal equilibrium. The predicted lattice parameters of the Fe–C martensites are in a good agreement with the experimental data. However, the preparation procedures of the austenites at room temperature, causes crystal defects thereby dropping the experimental values by 0.25% from the purely ideal predicted values. The model also yield the tetragonality (c/a) of the martensite as a function of C atoms/100 Fe atoms, defined by the ideal ratio c/a = 1 + 0.01X_C.     

Thermodynamic assessment of the Nd–Zn binary system

On the basis of available experimental information, the Nd–Zn binary system has been thermodynamically optimized using the CALPHAD method. The solution phases, liquid, bcc and dhcp, were treated as substitutional solutions, while the intermediate compounds, NdZn, NdZn₂, NdZn₃, Nd₃Zn₁₁, Nd₁₃Zn₅₈, Nd₃Zn₂₂, Nd₂Zn₁₇ and NdZn₁₁, were described as stoichiometric phases. A set of self-consistent parameters formulating the Gibbs energies of various phases in this binary system was obtained. Most of experimental data on thermochemistry and phase diagram reported in the literatures were satisfactorily reproduced.     

The microstructures and mechanical properties of cast Mg–Zn–Al–RE alloys

The microstructures and mechanical properties of cast Mg–Zn–Al–RE alloys with 4 wt.% RE and variable Zn and Al contents were investigated. The results show that the alloys mainly consist of α-Mg, Al₂REZn₂, Al₄RE and τ-Mg₃₂(Al,Zn)₄₉ phases, and a little amount of the β-Mg₁₇Al₁₂ phase will also be formed with certain Zn and Al contents. When increasing the Zn or Al content, the distribution of the Al₂REZn₂ and Al₄RE phases will be changed from cluster to dispersed, and the content of τ-Mg₃₂(Al,Zn)₄₉ phase increased gradually. The distribution of the Al₂REZn₂ and Al₄RE phases, and the content of β- or τ-phase are critical to the mechanical properties of Mg–Zn–Al–RE alloys. The Mg–6Zn–5Al–4RE alloy with cluster Al₂REZn₂ phase and low content of β-phase, exhibits the optimal mechanical properties, and the ultimate tensile strength, yield strength and elongation are 242 MPa, 140 MPa and 6.4% at room temperature, respectively.     

Thermodynamic modeling of the Ba–Ni–Ti system

The binary Ba–Ni and Ba–Ti systems are modeled by computational thermodynamics using the CALculation of PHAse Diagram (CALPHAD) method, wherein the thermodynamic parameters of disordered bcc, fcc and hcp phases are evaluated in terms of the first-principles calculations using the special quasirandom structures (SQSs). In combination with the Ni–Ti system modeling in the literature, the phase equilibria of the Ba–Ni–Ti system are predicted. Isothermal section of the ternary system is presented.