Binary Alloy Phase Diagrams Research Articles

Electrochemical diagrams showing equilibrium cathodic phases and their compositions as function of electrolyte composition and type of alloy phase diagram

In this paper the dependence of the elemental and phase compositions of the binary A-B cathodic deposits are computed by constructing “Electrochemical Diagrams”, abbreviated as ECDs, which potentially have a high practical significance. An ECD shows phases and compositions of cathodic alloy products as function of electrolyte composition at fixed temperature, pressure and at low current density upon galvano-static electrochemical co-deposition of components A-B from the same electrolyte on an inert cathode. The following rules are established here to construct the ECDs for binary A-B alloys: i). among all possible cathodic phases the one will be electrodeposited that provides the least negative cathodic deposition potential, ii). two or three (but not four or more) phases can be co-deposited on the cathode if their equilibrium cathodic potentials are equal and are the least negative among all possible cathodic phases, iii). the equilibrium compositions of solid and liquid A-B alloys that form on the cathode can be found from the condition of equality of the partial equilibrium cathodic potentials of components A and B. Based on the above three rules, ECDs are constructed for some basic types of binary equilibrium alloy phase diagrams with the composition of the alloy on its y-axes as function of the ionic composition of the electrolyte on its x-axes. In all cases the clear connection is shown between the ECDs and their corresponding alloy phase diagrams. The following geometric features are established for ECDs: i). solution phases are characterized by continuous curves, ii). phases of fixed compositions are characterized by horizontal lines, iii). two-phase mixtures are characterized by vertical lines, iv). three-phase equilibria are characterized by single points along the vertical lines corresponding to the two-phase equilibria of the parent phases of the third phase. It is shown that the restricted phase rule of Gibbs (= the maximum number of coexisting phases = the number of independent components + 1) is valid also for the ECDs. As examples, ECDs are calculated for the Ni-Co system and for the Ti-B system and good agreement is found between these calculated diagrams and the experimental data.

Novel valence regulation-vacuum gasification method for separation of selenium and tellurium

It is a general challenge to separate similar elements in material and non-ferrous metallurgical industries. Due to their unique semiconductor properties, selenium and tellurium as well as their separation have been increasingly drawing the attention of worldwide research. Currently, they are mainly extracted and recycled from copper anode slime. The conventional methods used for separating selenium and tellurium have several drawbacks, including low separation efficiency, lengthy processes, and significant environmental pollution. To address these issues, in this paper, the gas-liquid equilibrium (VLE) phase diagram of selenium-base binary alloy at full concentration was drawn according to the theory of gas-liquid equilibrium, the limitation of single vacuum distillation separation technique is theoretically interpreted, and a novel valence regulation-vacuum gasification method is proposed, which shows a superior selenium/tellurium separation rate of 99.98 % and a high material volatilization rate around 90 % achieved with hydrogen peroxide addition. The optimal amount of hydrogen peroxide for the separation process is determined as 1.1 L/kg. The promising results suggest potential of the new method for effectively separating other similar elements.

Investigation of the Pd(1−x)Zn x alloy phase diagram using ab initio modelling approaches

The identification of the stable phases in alloy materials is challenging because composition affects the structural stability of different intermediate phases. Computational simulation, via multiscale modelling approaches, can significantly accelerate the exploration of phase space and help to identify stable phases. Here, we apply such new approaches to understand the complex phase diagram of binary alloys of PdZn, with the relative stability of structural polymorphs considered through application of density functional theory coupled with cluster expansion (CE). The experimental phase diagram has several competing crystal structures, and we focus on three different closed-packed phases that are commonly observed for PdZn, namely the face-centred cubic (FCC), body-centred tetragonal (BCT) and hexagonal close packed (HCP), to identify their respective stability ranges. Our multiscale approach confirms a narrow range of stability for the BCT mixed alloy, within the Zn concentration range from 43.75% to 50%, which aligns with experimental observations. We subsequently use CE to show that the phases are competitive across all concentrations, but with the FCC alloy phase favoured for Zn concentrations below 43.75%, and that the HCP structure favoured for Zn-rich concentrations. Our methodology and results provide a platform for future investigations of PdZn and other close-packed alloy systems with multiscale modelling techniques.

The Equilibrium α (Al-Li Solid Solution) and Metastable δ′ (Al3Li) Phase Boundaries in Aluminum–Lithium Alloys

Data on the equilibrium solubilities of the α Al-Li solid solution phase and the ordered metastable δ′ Al3Li (L12 crystal structure) precipitate phase are critically reviewed, and a new binary alloy phase diagram is proposed. The δ′ solvus, describing the equilibrium solubility of Li in the α phase, Xαe, in atom fraction Li, is given by the equation X_{alpha e} , = ,0.{6}00{text{86 exp}}left{ {{-}{8669}.{55}/{text{R}}T} right}, where R is the gas constant, and the temperature T is in K. The α solvus, i.e. the equilibrium solubility of Li in the δ′ phase, Xδ′e, is given by the equation X_{delta prime e} , = ,0.{18}0{9}, + ,{6}.{413}, times ,{1}0^{{{-}{4}}} {{T}}{-}{1}.{861}, times ,{1}0^{{{-}{6}}} T^{{2}} , + ,{1}.{4684}, times ,{1}0^{{{-}{9}}} T^{{3}} , which represents a compromise between previously published theoretical curves that predict retrograde behavior. It is emphasized that that all the data cited and re-analyzed exclusively involve binary Al-Li alloys. The new phase diagram eliminates data that were previously mis-attributed. Most importantly, it is informed by considerable re-analysis of previously published data, supplemented by the inclusion of data that were not previously considered, and eschews data on both Xαe and Xδ′e that are indubitably non-equilibrium in nature.

Effect of Solute Carbon on the Characteristic Hardening of Steel at High Temperature

Small ball rebound hardness tests demonstrated characteristic hardening at 700 K in the ultra-low carbon and pearlitic steels. The equilibrium phase diagram of Fe-C binary alloy calculated using Thermo-Calc exhibited dissolving of cementite above 700 K. Moreover, in-situ heating neutron diffraction measurement demonstrated the increase of lattice parameter by dissolving of cementite above 700 K. Therefore, it can be concluded that the characteristic hardening above 700 K can be attributed to the solid solute carbon.

Impact of microalloying element Ga on the glass-forming ability (GFA), mechanical properties and corrosion behavior of Mg–Zn–Ca bulk metallic glass

By virtue of its high corrosion resistance and desirable mechanical properties, Mg-based bulk metallic glass (BMG) is a promising candidate material for the biodegradable implants. To investigate the impact of microalloying element Ga on the glass-forming ability (GFA) and its effect on the mechanical properties and corrosion behaviors of Mg–Zn–Ca BMG, a series alloys of (Mg66Zn30Ca4)100-xGax (x = 0, 0.25, 0.5, 0.75, 1.0 and 1.25) were synthesized and investigated in this study. According to the XRD results and SEM (backscattered electron) images, the critical diameter (Dc) of Mg66Zn30Ca4 BMG is about 3.5 mm, and 1.0 at.% Ga addition improves the Dc to about 5 mm. Meanwhile, the 1.0 at.% Ga addition improves the fracture strength of Mg–Zn–Ca BMG from 651 MPa to 752 MPa. The corrosion behavior and mechanism of different metallic glass samples were investigated. According to the results of electrochemical tests and immersion test, the addition of Ga can help to form the passive film on the metallic glass substrate and improve its corrosion resistance. Besides, the relationship between the alloy composition and glass-forming ability (GFA) was postulated and interpreted by the theory of binary alloy phase diagrams.

Plotting phase diagrams of binary alloys and justification of their industrial use

Binary eutectic solutions are analyzed as a foundation for a Generalized Lattice Model of each component. Phase transitions of binary solutions depending of concentration of its components and temperature are determined with equations for invariant two-phase equilibriums by construction of binary-phase diagrams. The paper demonstrates a possibility to construct binary-phase diagrams with minimal error with respect to reference sources. An example of cadmium-zinc alloy is used to show changes in its characteristics depending on percentages of its components. An application is suggested for items with cadmium-zinc coating.

Interfacial characterization of dissimilar-metals bonding between vanadium alloy and Hastelloy X alloy by explosive welding

Dissimilar-metals bonding between V–4Cr–4Ti and Hastelloy X alloy was investigated by explosive welding, which is essential to connect coolant pipes of Flibe blanket and external components such as tritium extractor and heat exchanger in fusion reactor. The nano-indentation hardness and corresponding microstructure at the interface are evaluated. After the explosive welding, a characterization of the typical wavy interface indicates good weldability. Discontinuous vortex regions appear at the interface and reveal obvious hardening up to 806 HV. Microstructural analysis indicates that the interlayer consists of Ni37.1V21Cr20.5Fe15.4Mo4.4Ti1.0 Co0.6 with a fcc lattice structure and a high density of dislocations, and no intermetallic forms. Based on the compositions, the formation of solid solution was predicted by the entropy and enthalpy of the multi-component alloy system, despite the phase diagrams of binary alloys of the constituent elements indicating the formation of intermetallics. Study of hardening mechanism at the interlayer indicates that obvious hardening is mainly attributed to solid-solution hardening and dislocation hardening.

Supplemental Literature Review of Binary Phase Diagrams: Au-La, Ce-Pt, Co-Pt, Cr-S, Cu-Sb, Fe-Ni, Lu-Pd, Ni-S, Pd-Ti, Si-Te, Ta-V, and V-Zn

Recent literature on Au-La, Ce-Pt, Co-Pt, Cr-S, Cu-Sb, Fe-Ni, Lu-Pd, Ni-S, Pd-Ti, Si-Te, Ta-V, and V-Zn phase diagrams is reviewed in this article in order to update the 1990 compilation Binary Alloy Phase Diagrams, 2nd edition, by T.B. Massalski, et al. For some systems reaction tables and crystal structure data have been included, as well. Diagrams have been checked for consistency with rules for phase diagram construction and modified when necessary. In addition, diagrams needing more work have been identified.

Effect of pressure on the interactions and phase diagrams of binary alloys

The phase diagrams of binary alloys have been found to vary with pressure. Within the framework of solution-type models, the variation is controlled by the pressure dependence of the elemental end members, which is relatively well known, and that of the excess interaction, which is relatively unknown. Exact thermodynamic relationships for the pressure and temperature dependence of the interaction parameters in an alloy solution are developed and related to the composition dependence of the excess thermodynamic quantities measured at ambient conditions. The effect of pressure modification of the interaction parameter on phase diagrams and solubility limits is explored in model systems identifying the critical role of the excess volume. It is found that the most significant pressure effects on the phase diagram are to be expected when the critical temperature associated with the solid solution interaction parameter is similar to the melting temperatures of the end-members and the excess volume of the is large.

CoPt-Co hybrid supported on amino modified SiO2 nanospheres as a high performance catalyst for hydrogen generation from ammonia borane

CoPt-Co hybrids were successfully supported on amino modified SiO2 nanospheres by a chemical reduction method at a temperature of 278 K. The solid carrier i.e. amino modified SiO2, provides numerous anchoring sites for the metal nanoparticles (NPs) to improve the dispersion while reducing the size of metal NPs. The supported NPs displayed a narrow particle size distribution on the SiO2 surface with an average diameter of 12 nm. The XRD results alongside with the binary alloy phase diagram suggest that the resulted NPs are bimetallic, composed of CoPt and amorphous Co. Among the prepared materials, the solid with the specific composition of SiO2@Pt0.1Co0.9 was proved to be effective catalyst for ammonia borane (AB) hydrolysis in aqueous solution. The turnover frequency (TOF) value of the supported nanocatalyst was 25.59 molH2⋅min−1⋅molM−1, almost twice as that of unsupported Pt0.1Co0.9 NPs while the activation energy was 37.05 kJ mol−1. Furthermore, the SiO2@Pt0.1Co0.9 composite manifested high catalytic activity even after five cycles of reuse.

Microstructure and mechanical property of a novel ReMoTaW high-entropy alloy with high density

This work focuses on a novel high-entropy alloy, ReMoTaW, with high density of 16.69 × 103 kg/m3. The high-entropy alloy displays three disordered solid solution phases. The phase segregation is explained by binary alloy phase diagrams and melting point temperature differences during non-equilibrium solidification. The maximum strength, failure strain and hardness are, respectively, 1451 MPa, 5.69% and 640 HV.

Phase Diagram of a Binary Alloy in the Static Concentration Wave Approximation

The three-sublattice ordering observed in alloys used for special purpose hard magnets is considered. Possible phase diagrams describing the ordering of alloys in systems of intermetallides with RCo2 structure are presented. It is shown that, according to the static concentration wave (SCW) approximation, the main area of the phase diagram is occupied by incongruently melting partially ordered alloys.

Phase diagrams of binary alloys under pressure

The phase diagrams of binary alloys are known to vary with pressure. Within the framework of solution-type models, the variation is controlled by the pressure dependence of the elemental end members, which is relatively well known, and that of the excess interaction, which is unknown. We develop an exact thermodynamic relationship for the pressure dependence of the excess interaction in an alloy solution and relate it to the composition dependence of the density and sound velocity measured at ambient pressure. The effect of composition on the sound velocity and density was studied for the isomorphous binary alloy BiSb and the eutectic systems BiSn and PbSn, and the pressure dependence of the excess interaction was evaluated. On the basis of these results, the pressure dependence of these binary alloy phase diagrams was calculated and found to agree well with the experimental data in the literature.

Estimation of thermodynamic properties of Cu–La binary alloy with modified Miedema’s theory

According to modified Miedema’s theory, mixing enthalpies (ΔH), excess entropies (SE), excess Gibbs free energy (GE), and component activities (a) of Cu–La binary alloy were estimated using the basic thermodynamic principles and some simple physical parameters of Cu and La, such as electronegativity, atomic volume and electron density. Based on the Cu–La binary alloy phase diagram, the Gibbs free energy of the phase precipitation reactions of Cu6La and Cu5La was deduced. The results showed that the values of ΔH, SE, and GE of Cu–La binary alloy were all negative. Compared to the ideal solution, the activities of the components presented a large negative deviation from Raoult’s law, which indicated that there was a strong interaction between Cu and La. The calculated data are well consistent with the experimental data. The Gibbs free energies of the phase precipitation reactions of Cu6La are lower than those for Cu5La, which means that Cu6La is thermodynamically more stable than Cu5La. Furthermore, the experimental results show that rareearth rich Cu6La phase particles in copper matrix are formed after La microalloying.

Supplemental Literature Review of Binary Phase Diagrams: B-La, B-Zn, Bi-La, Bi-Ti, Cd-Pr, Ce-Ga, Cu-Na, Ge-Ta, Ge-Y, H-Zr, Na-Si, and Pb-Sc

Binary Alloy Phase Diagrams, 2nd edition, a comprehensive collection of alloy phase diagrams for 2159 binary systems, was published in 1990 (T.B. Massalski, H. Okamoto, P.R. Subramanian, and L. Kacprzak., ASM International, Materials Park, OH [Massalski2]). This review intends to provide more recent information on the binary phase diagrams for the B-La, B-Zn, Bi-La, Bi-Ti, CdPr, Ce-Ga, Cu-Na, Ge-Ta, Ge-Y, H-Zr, Na-Si, and Pb-Sc systems that have become available after 1990. The criteria for selecting such information for inclusion in this review are (1) systems for which no phase diagram was given in [Massalski2], (2) complete diagrams that are substantially different from the earlier version, and (3) partial diagrams that alter or clarify the earlier version. Thermodynamic consistency of the new phase diagrams was checked based on phase rules and the diagrams were modified if necessary. However, each updated phase diagram has not gone through the ordinary evaluation process. Accordingly, a newer phase diagram is not always a better diagram, especially when there is too little published data on a system. For convenience, reaction tables and crystal structure data have been added when new information was available.

Supplemental Literature Review of Binary Phase Diagrams: Al-P, B-Ga, B-Nd, Ba-Ga, Bi-Cs, Ca-Ga, Cd-Gd, Cr-Mo, Gd-Ni, Ni-Pb, Ni-Sc, and Sc-Sn

Binary Alloy Phase Diagrams, 2nd edition, a comprehensive collection of alloy phase diagrams for 2159 binary systems, was published in 1990 (T.B. Massalski, H. Okamoto, P.R. Subramanian, and L. Kacprzak., ASM International, Materials Park, OH [Massalski2]). This review intends to provide more recent information on the binary phase diagrams for the Al-P, B-Ga, B-Nd, Ba-Ga, Bi-Cs, Ca-Ga, Cd-Gd, Cr-Mo, Gd-Ni, Ni-Pb, Ni-Sc, and Sc-Sn systems that have become available after 1990. The criteria for selecting such information for inclusion in this review are (1) systems for which no phase diagram was given in [Massalski2], (2) complete diagrams that are substantially different from the earlier version, and (3) partial diagrams that alter or clarify the earlier version. Thermodynamic consistency of the new phase diagrams was checked based on phase rules and the diagramsweremodified if necessary. However, each updated phase diagram has not gone through the ordinary evaluation process. Accordingly, a newer phase diagram is not always a better diagram, especially when there is too little published data on a system. For convenience, reaction tables and crystal structure data have been added when new information was available.

Nanophase diagram of binary eutectic Au-Ge nanoalloys for vapor-liquid-solid semiconductor nanowires growth

Although the vapor-liquid-solid growth of semiconductor nanowire is a non-equilibrium process, the equilibrium phase diagram of binary alloy provides important guidance on the growth conditions, such as the temperature and the equilibrium composition of the alloy. Given the small dimensions of the alloy seeds and the nanowires, the known phase diagram of bulk binary alloy cannot be expected to accurately predict the behavior of the nanowire growth. Here, we developed a unified model to describe the size- and dimensionality-dependent equilibrium phase diagram of Au-Ge binary eutectic nanoalloys based on the size-dependent cohesive energy model. It is found that the liquidus curves reduce and shift leftward with decreasing size and dimensionality. Moreover, the effects of size and dimensionality on the eutectic composition are small and negligible when both components in binary eutectic alloys have the same dimensionality. However, when two components have different dimensionality (e.g. Au nanoparticle-Ge nanowire usually used in the semiconductor nanowires growth), the eutectic composition reduces with decreasing size.

Study on Mechanism of Phase Forming in Ni<sup>+</sup> Implantation into Ti6Al4V at Elevated Temperature

Recently, due to the prediction of the forming phase only focuses on the case which a simple metal ion implants into a single metal matrix, we will study that a simple metal ion is implanted into alloy matrix in this paper. The forming phases in Ni+implantation into Ti6Al4V at elevated temperature will be predicted by the effective heat of formation (EHF) model. The results show that the prediction is consistent with the experimental findings, the first-phase is TiNi with the most negative EHF, the second-phase is Ti2Ni which component concentrations of Ni limited element is lower and locates on the left in the Ti-Ni binary alloy phase diagram, and the TiNi3phase is not found in the experiment. Simultaneously, we explain correctly why the Ni-Al or Ni-V phases don’t generate in Ni+implantation into Ti6Al4V at elevated temperature.

A Critical Assessment of Thermodynamic and Phase Diagram Data for the Ge-O System

A critical assessment of the thermodynamic and phase diagram data for the crystalline and liquid phases of the Ge-O system at ambient pressures has been carried out to provide a set of parameters which can be used as a basis for the calculation of ternary and multicomponent phase equilibria. The phase diagram reported by Massalski (Binary Alloy Phase Diagrams, ASM International, Materials Park, 1990) does not correctly reproduce the rather limited experimental information for the system. There is some inconsistency between the rather more extensive experimental thermodynamic data for the three phases of GeO2 stable at ambient pressures.