The Al-Er-Mg ternary system Part I: Experimental investigation

Investigation of phase equilibria in the ternary system Al-Er-Mg has been carried out by means of differential thermal analysis (DTA), powder x-ray diffraction (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM), and quantitative electron probe microanalysis (EPMA). The isothermal section at 400 °C has been established. An extended homogeneity region with Al substitution for Mg at a constant Er content has been found for (Mg_1−x Al _x )Er (0≤x≤0.78); a few other boundary binary phases give lower ternary solubility. A ternary compound, τ, of Al_66.7Er₁₀Mg_23.3 stoichiometry, has been found to exist in the isothermal section at 400 °C.     

The Al-Er-Mg ternary system Part I: Experimental investigation

Investigation of phase equilibria in the ternary system Al-Er-Mg has been carried out by means of differential thermal analysis (DTA), powder x-ray diffraction (XRD), light optical microscopy (LOM), scanning electron microscopy (SEM), and quantitative electron probe microanalysis (EPMA). The isothermal section at 400 °C has been established. An extended homogeneity region with Al substitution for Mg at a constant Er content has been found for (Mg_1−x Al _x )Er (0≤x≤0.78); a few other boundary binary phases give lower ternary solubility. A ternary compound, τ, of Al_66.7Er₁₀Mg_23.3 stoichiometry, has been found to exist in the isothermal section at 400 °C.     

Thermodynamic study of phase equilibria in the Ni-Si-B system

A thermodynamic analysis of the phase equilibria in the Ni-Si-B ternary system was conducted. A regular solution approximation based on a sublattice model was adopted to describe the Gibbs energies for the individual phases in the binary and ternary systems. A set of thermodynamic parameters for the individual phases was evaluated from literature data on phase boundaries and thermochemical properties. The optimized parameters reproduced the experimental data, for the most part, satisfactorily. However, in the calculated isothemal section at 850 °C, phase equilibria between the fcc phase and Ni₆Si₂B or Ni₃Si(β ₁) and Ni₆Si₂B were found instead of the experimentally observed equilibria between Ni₃Si(β ₁) and Ni₃B or Ni₅Si₂(γ) and Ni₃B. Further, in the primary crystal surface for the fcc phase, the calculated liquidus temperatures were higher than the reported values by approximately 80 °C. Therefore, it is considered that the fcc phase evaluated in the Ni-Si system by Lindhólm and Sundman is too stable.     

Thermodynamic study of phase equilibria in the Ni-Si-B system

A thermodynamic analysis of the phase equilibria in the Ni-Si-B ternary system was conducted. A regular solution approximation based on a sublattice model was adopted to describe the Gibbs energies for the individual phases in the binary and ternary systems. A set of thermodynamic parameters for the individual phases was evaluated from literature data on phase boundaries and thermochemical properties. The optimized parameters reproduced the experimental data, for the most part, satisfactorily. However, in the calculated isothemal section at 850 °C, phase equilibria between the fcc phase and Ni₆Si₂B or Ni₃Si(β ₁) and Ni₆Si₂B were found instead of the experimentally observed equilibria between Ni₃Si(β ₁) and Ni₃B or Ni₅Si₂(γ) and Ni₃B. Further, in the primary crystal surface for the fcc phase, the calculated liquidus temperatures were higher than the reported values by approximately 80 °C. Therefore, it is considered that the fcc phase evaluated in the Ni-Si system by Lindhólm and Sundman is too stable.     

Fabrication and its characteristics of hard coating Ti-Al-N system prepared by DC magnetron sputtering

Pseudobinary Ti1-xAlxN films were synthesized on Si (100) wafer by DC magnetron sputtering method using Ti1-dAlx alloy targets with different Al contents. The composition of the Ti1-AlxN films was determined by electron probe microanalysis (EPMA). Structural characteristic was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). First principles virtual crystal calculations for the Ti1-xAlxN disordered alloys were used for the XRD simulations. The crystalline structure of the Ti0. 61Al0. 39N film was found to be a metastable single phase with NaCl (B1) structure. Its lattice constant, determined by XRD, was less than that of pure TiN. With the increase of Al content, the lattice constant of B1 phase was continually decreased, while würtzite (B4) structure was observed in the Ti0. 40Al0. 60N film. When x reached 0. 75, the B1 phase disappeared, and only 34 phase was remained. The critical Al content for the phase transition from NaCl to würtzite structure in this paper was about 0. 60, which could be explained by both the thermodynamic model and the electron theory. As-deposited Ti1-xAlxN films exhibited excellent mechanical properties. Hardness measurements of Ti1-xAlxN films showed a high value of 45GPa for x=0. 39 and was decreased to value of 27 Gpa with increasing Al at x=0. 60.     

Critical assessment and thermodynamic calculation of the ternary system C-Hf-Zr (Carbon-Zirconium-Hafnium)

Based on an assessment of the available experimental thermochemical and phase diagram information available, the phase equilibria of the C-Hf-Zr system were calculated. The G of the individual phases was described with thermodynamic models. The liquid phase was described as a substitutional solution using the Redlich-Kister formalism for excess G. Graphite was treated as a stoichiometric phase. The solid solutions of carbon in α(Hf,Zr) and β(Hf,Zr), as well as the non-stoichiometric phase (Hf,Zr)C_1−x, were represented as interstitial solid solutions using the compound energy model with two sublattices. The parameters in the models were determined by computerized optimization using selected experimental data. A detailed comparison was made between calculation and experimental data.     

Solid-state phase equilibria in the Titanium-Aluminum-Nitrogen system

The 1273K isothermal section of the Ti-Al-N phase diagram was studied using modern methods of physical and chemical analyses. The data obtained by various techniques are in good agreement and in harmony with the results of thermodynamic calculations. It has been reliably established that AIN can coexist with TiN_1−x , Ti₂AIN, and TiAl₃; the ternary nitride Ti₂AIN can be in equilibrium with TiAl₃, AIN, TiAl₂, TiAl, TiN_1−x , and Ti₃AIN; the solid solution based on α(Ti) coexists with Ti₃Al, Ti₃AIN, TiN_1−x , and Ti₂N. Literature data on phase equilibria in the Ti-Al-N system were analyzed, and a 1273 K isothermal section of the phase diagram has been suggested.     

Effect of dysprosium and cobalt on the temperature dependence of magnetization and phase composition of a material of the Nd-Dy-Fe-Co-B system

Sintered magnetically hard materials with composition (Nd_1−x Dy_x)_13–16(Fe_1−y Co_y)_resAl_0.5−1B_7–9 (x = 0.11–0.71, y = 0.19–0.34) are investigated. The role of cobalt and dysprosium in the variation of magnetic properties of the material (residual induction, coercive force) is studied. The phase composition of the material and its effect on magnetic properties are determined. Amethod for computing the induction temperature coefficient of a material on the basis of published data on the physical characteristics (the Curie temperature, the density, the molecular mass) of the main magnetic phase (Nd, Dy)₂(Fe, Co)₁₄B is presented. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 3–10, April, 2007.     

Thermodynamic optimization of the Ni-Zn system

Optimization of thermodynamic and phase diagram data has been performed and consistent sets of coefficients for the calculation of the phase equilibria in the system Ni-Zn have been obtained using the program BINGSS. The δ phase has been modeled as a stoichiometric compound (NiZn₈). The binary liquid and the solid Ni-based solutions have been treated as disordered substitutional phases. The intermediate β, β ₁, and γ compounds have been modeled as phases with substitutional defects and vacancies on two sublattices. The calculated phase diagram and thermodynamic quantities are in excellent agreement with the experimental data.     

Experimental analysis and thermodynamic calculation of the structural regularities in the fusion diagram of the system of alloys Al-Mg-Si

Sections of the phase diagram Al-Mg-Si with up to 35 at.% magnesium and 35 at.% silicon are constructed. The thermodynamic calculation and experimental analysis have shown that the conode of three-phase eutectic equilibrium L ⇔ α-Al+Mg₂Si, corresponding to the maximum temperature of eutectic transformation, does not coincide with the stoichiometric cross section between Al and Mg₂Si in the Al-Mg-Si ternary system, but rather occurs toward the magnesium-rich side of the ternary diagram. A polythermal cross section, corresponding to this conode, has been constructed. Concentration-temperature parameters of the univariant eutectic transformation L ⇔ α-Al+Mg₂Si, as well as the boundaries of the domain of existence of alloys crystallizing with the formation of only two phases, namely, α-Al and Mg₂Si, were determined. Modeling of phase equilibria involving solid and liquid phases in the ternary system Al-Mg-Si was carried out. The topology of the phase diagram is stable against a wide range variation of the adjustable parameters; the inherent form of the diagram seems well established. The reasons for this are discussed.     

Reassessment of Ni-Al and Ni-Fe-Al solidus temperatures

Solidus temperatures of the B2 NiAl phase have been determined by high-temperature differential thermal analysis for binary melt compositions Ni_xAl_100−x (45<x<57) and for ternary alloys Fe_yNi_50−yAl₅₀ (0≤y≤50). It was shown that the melting temperature of the stoichiometric Ni₅₀Al₅₀ phase is 1681 °C, which is 43 K higher than some literature data. The solidus line at the Ni-rich side of the Ni-Al phase diagram exhibits a steeper slope than that reported previously. Substituting Fe for Ni, the decrease of solidus temperature along the isoplethal section with 50 at.% Al of the ternary Ni-Fe-Al phase diagram exhibits a steep initial slope of −13 K/at.% Fe for small Fe-fractions, which changes into a nearly linear decrease with an average slope of −8.5 K/at.% Fe.     

The Heusler Phase Ti25(Fe50 − x Ni x )Al25 (0 ≤ x ≤ 50); Structure and Constitution

Alloys with composition Ti₂₅(Fe_50 − x Ni _x )Al₂₅ (0 ≤ x ≤ 50) were investigated employing electron probe microanalysis (EPMA) and X-ray powder diffraction (XPD). For TiFe₂Al, in situ neutron powder diffraction (ND) was used for the inspection of phase constitution covering the temperature range from 27 °C (300 K) to 1277 °C (1550 K). Combined Rietveld refinement of ND and XPD data for TiFe₂Al revealed that Fe atoms occupy the 8c site in space group Ti with a small amount of Al sharing the 4a site, and the remaining Ti and Al atoms adopting the 4b site. This structural model was successfully applied in the refinement of all alloys Ti₂₅(Fe_50 − x Ni _x )Al₂₅ (0 ≤ x ≤ 50). Partial atom order exists on the Fe-rich side while complete order is observed for the Ni-rich side. Profiles recorded by in situ neutron powder diffraction for TiFe₂Al in the range of investigated temperatures show two phases, namely Heusler phase and MgZn₂-type Laves phase. Diffraction peaks from the Heusler phase dominate the profiles at lower temperatures but at higher temperatures the MgZn₂-type Laves phase is the main phase. No CsCl-type phase was found in the alloy in the investigated temperature range. The thermal expansion coefficient of TiFe₂Al is 1.4552 × 10⁻⁵ K⁻¹.     

Experimental analysis and thermodynamic calculation of the structural regularities in the fusion diagram of the system of alloys Al-Mg-Si

Sections of the phase diagram Al-Mg-Si with up to 35 at.% magnesium and 35 at.% silicon are constructed. The thermodynamic calculation and experimental analysis have shown that the conode of three-phase eutectic equilibrium L ⇔ α-Al+Mg₂Si, corresponding to the maximum temperature of eutectic transformation, does not coincide with the stoichiometric cross section between Al and Mg₂Si in the Al-Mg-Si ternary system, but rather occurs toward the magnesium-rich side of the ternary diagram. A polythermal cross section, corresponding to this conode, has been constructed. Concentration-temperature parameters of the univariant eutectic transformation L ⇔ α-Al+Mg₂Si, as well as the boundaries of the domain of existence of alloys crystallizing with the formation of only two phases, namely, α-Al and Mg₂Si, were determined. Modeling of phase equilibria involving solid and liquid phases in the ternary system Al-Mg-Si was carried out. The topology of the phase diagram is stable against a wide range variation of the adjustable parameters; the inherent form of the diagram seems well established. The reasons for this are discussed.     

Thermodynamic optimization of the Ni-Zn system

Optimization of thermodynamic and phase diagram data has been performed and consistent sets of coefficients for the calculation of the phase equilibria in the system Ni-Zn have been obtained using the program BINGSS. The δ phase has been modeled as a stoichiometric compound (NiZn₈). The binary liquid and the solid Ni-based solutions have been treated as disordered substitutional phases. The intermediate β, β ₁, and γ compounds have been modeled as phases with substitutional defects and vacancies on two sublattices. The calculated phase diagram and thermodynamic quantities are in excellent agreement with the experimental data.     

Microstructure and phase composition of as-cast Mg–9Er–6Y–xZn–0.6Zr alloys

The microstructure and phase composition of as-cast Mg–9Er–6Y–xZn–0.6Zr (x=1, 2, 3, 4; normal mass fraction in %) alloys were investigated. In low Zn content, aside from the major second phase of Mg₂₄(Er, Y, Zn)₅, there are a few lamellar phases that grow parallel with each other from the grain boundaries to the grain interior. With Zn content increasing, the Mg₂₄(Er,Y,Zn)₅ phase decreases, but the Mg₁₂Zn(Y, Er) phase and lamellar phases continuously increase. When Zn content reaches 4% (normal mass fraction), the Mg₁₂Zn(Y,Er) phase mainly exists as large bulks, and some α-Mg grains are thoroughly penetrated by the lamellar phases. Moreover, the crystallography structures of the Mg₁₂Zn(Y,Er) and Mg₂₄(Er,Y,Zn)₅ phases are confirmed as 18R-type long-period stacking ordered structure and body-centred cubic structure, respectively.     

Thermodynamic Description of $${\hbox{SrO-Al}_{2}\hbox{O}_{3}}$$ System and Comparison with Similar Systems

The Al₂O₃-SrO binary system has been studied using the CALPHAD technique in this paper. The modeling of Al₂O₃ in the liquid phase is modified from the traditional formula with the liquid phase represented by the ionic two-sublattice model as (Al³⁺, Sr²⁺) _P (, O²⁻) _Q . Based on the measured phase equilibrium data and experimental thermodynamic properties, a set of thermodynamic functions has been optimized using an interactive computer-assisted analysis. The calculated results are compared with experimental data. A comparison between this system and similar systems is also given.     

Assessment of the Sr-Mn-O system

A thermodynamic assessment of the Sr-Mn-O system is presented. The main practical relevance of this system is that it contains the perovskite phase SrMnO₃, which is the Sr-rich end member of the phase (La,Sr) MnO₃, that finds widespread use as a cathode material for solid oxide fuel cells (SOFCs) and has recently attracted a lot of attention due to its interesting giant magnetoresistive properties. The thermodynamic parameters are optimized by applying the CALPHAD method. The SrMnO_3−z phase exists in two modifications, a layered hexagonal modification at low temperatures and a perovskite modification at high temperatures. Both modifications show considerable oxygen deficiencies, which are modeled using the compound energy model. The sublattice occupation of the phases is (Sr²⁺) (Mn³⁺, Mn⁴⁺)(O²⁻, Va)₃. On reducing Mn⁴⁺ to Mn³⁺, oxygen vacanices are formed. The phase SrMn₃O_6−z also shows an oxygen deficiency, which is modeled in an identical way. The Ruddlesden-Popper phases Sr₂MnO₄ and Sr₃Mn₂O₇, and the phases Sr₇Mn₄O₁₅ and Sr₄Mn₃O₁₀ are modeled as stoichiometric phases. The ionic liquid is modeled using the two-sublattice model for ionic liquids. The stability and thermodynamic data on many of the phases in this system are poorly known. For this reason, some aspects of this assessment must be regarded as tentative.