Phase diagram of Ni3V-Co3V pseudobinary system

A phase diagram of Ni₃V-Co₃V pseudobinary system is proposed based on x-ray diffraction and differential thermal analysis. Four invariant reactions are located in the phase diagram—two eutectoid and two peritectoid reactions. Six kinds of geometrically close-packed phases are encountered. The stability of these close-packed phases correlate well with the electron concentration.     

Phase equilibria in the binary Rh–Ti system

The present study of the binary Ti–Rh system provides a revised phase diagram clarifying controversial results in the literature. Various experimental methods were applied: electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. The tie-lines of two-phase equilibria and the second-order transition A2/B2 were identified by means of diffusion couple experiments and by analysis of annealed bulk alloys. The diffusion couple experiments revealed two phenomena which were identified as pseudo-interfaces: one associated with crossing the stoichiometric composition of the B2 phase; a second between pure Rh and the Rh-rich solution.     

Phase equilibria and phase transformations in the Ti-rich corner of the Fe–Ni–Ti system

While the main features of the Fe–Ni–Ti system are well known at low Ti content, literature review of the Ti-rich corner revealed inconsistencies between experimental reports. This investigation presents new experimental results, defined to remove the uncertainties concerning melting behavior and solid-state phase equilibria of the (Ni,Fe)Ti₂ phase with the adjacent (Fe,Ni)Ti (B2, CsCl-type structure) and β-Ti (A2, W-type) phases. Six samples have been prepared and examined by differential thermal analysis performed in yttria and alumina crucibles, and by scanning electron microscopy in the as-cast state as well as equilibrated at 900 °C.     

Structural study of the pseudobinary Y(Ni,Cu)2 system

The pseudobinary Y(Ni_1−xCu_x)₂ compounds have been investigated by X-ray and neutron diffraction, density measurements as well as with electron probe microanalysis. The goal was to understand the mechanism behind the structural change from the cubic structure of Y_0.95Ni₂ (a cubic superstructure of the cubic Laves phase with ordered vacancies on the Y site) into the orthorhombic CeCu₂ type structure of YCu₂. 20% of Cu can be substituted for Ni in Y_0.95Ni₂ accompanied by an increase of the number of Y vacancies in the cubic superstructure. On the Cu-rich side a solid solution was found from YCu₂ to Y(Ni_0.5Cu_0.5)₂. The substitution for Ni in the orthorhombic structure mainly causes a decrease of the lattice parameter a, giving rise to a 3.5% contraction of the unit cell volume. These two solid solutions are separated by a two-phase region. The thermal expansion among the cubic compounds hardly changes with the Cu concentration, whereas it increases in the orthorhombic range towards YCu₂.     

Phase equilibria in the Ga- In- Ni system at 600 °C

Phase equilibria are established in the Ga-In-Ni system at 600 °C using X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA). The system is characterized by a notable absence of ternary solubility among the constituent binary phases. The only exception is the phase Ni₂ln₃, which dissolves a maximum of 12.7 at% Ga. Two ternary phases exist in the compositional vicinity of γ TVi₁₃Ga₉ and Ni₅Ga₃, both of which contain approximately 10 at.% In. These phases are considered to be superlattice structures derived from that of the binary, high-temperature phase γNi₃Ga₂, which possesses a partially filled NiAs (B8₁) structure. The phase diagram isotherm determined in the present investigation was also compared with an isotherm calculated using experimental thermodynamic data for the constituent binary phases, which are available in the literature. The calculated and experimental isotherms agree well.     

Phase equilibria in the Ni-rich portion of the Ni–Ga binary system

The phase equilibria in the composition range from 0 to 60 at% Ga of the Ni–Ga system were determined by electron probe microanalysis (EPMA) using diffusion couples, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). It was found that while the phase equilibria between the α′ (L1₂: Ni₃Ga) and α (Ni-solid solution) or β (B2: NiGa) phases are basically in agreement with the diagram evaluated by Lee and Nash, those between γ (B8₁: Ni₁₃Ga₇), δ (Cmmm: Ni₅Ga₃) and ɛ (C2/m: Ni₁₃Ga₉) are topologically different from that diagram. Three eutectoid reactions (γ → δ + ɛ, β → γ + ɛ, β → α′ + γ) and one peritectoid reaction (α′ + γ → δ) were confirmed and the temperatures and concentrations of those invariant reactions were determined.     

Phase equilibria in the Fe–Rh–Ti system II. CVM calculations

Cluster Variation Method (CVM) calculations of phase equilibria in the bcc Fe–Rh–Ti system were performed in the irregular tetrahedron (IT) approximation including tetrahedron interactions. The energy parameters were obtained from a fit to recent experimental data on phase equilibria at 1000 °C and 800 °C. At these temperatures the ordering between first nearest neighbours dominates leading to large single-phase fields with B2 ordering. At lower temperatures the calculations predict additional ordering between second nearest neighbours of type D0₃. In the Fe–Ti system the second neighbour interactions are of segregation type leading to miscibility gaps between the disordered A2 and the ordered B2 phases extending from the binary Fe–Ti system into the ternary system. Calculated isothermal sections are presented at several temperatures. The complex ordering in the ternary system leads to strong variations of chemical potentials with composition. This is shown by calculated iso-chemical potential contours.     

Phase equilibria in the Fe–Rh–Ti system I. Experimental results

Two isothermal sections of the ternary system Fe–Rh–Ti were determined experimentally at 1000 °C and 800 °C using annealed alloys and diffusion couples. No ternary compound was found in this system. The B2 ordered phase is stable in all three binary subsystems of the Fe–Rh–Ti system and forms a range continuous solid solution at both temperatures. At 800 °C the B2-phase exhibits a tetragonal structure at certain ranges of composition. The same structure was observed in the binary Ti–Rh system. Within the B2 phase domain pseudo-interfaces were observed when the diffusion path crosses equiatomic compositions. A large miscibility gap between A2 and B2 was observed in the Fe-rich part of the Fe–Rh–Ti system.     

Phase equilibria and microstructures in the Fe–Si–Cr–Ti system

Having known that the (A2+D0₃) two-phase microstructure is obtained at below 873 K in the ternary Fe–Si–Cr alloy with 12–15 at.%Si at constant 10 at.%Cr, the effect of Ti additions to the ternary system on the possibility of having Huesler L2₁ phase in addition to D0₃ phase is examined. Microstructures of the quaternary Fe–10 and 12 at.%Si–10 at.%Cr–0.5 and 1 at.%Ti alloys are investigated by transmission electron microscopy through which identification and morphology of the phases precipitating within the A2 matrix are examined. It is found that the Ti addition to the ternary Fe–Si–Cr system provides (A2+L2₁) two-phase and/or (A2+D0₃+L2₁) three-phase regions. Morphology of the L2₁ phase is spherical or cuboidal, while that of D0₃ precipitates is rod-like, a difference which may be explained by the difference in magnitude of the misfit between the precipitate and the A2 matrix caused by the difference in partitioning of Ti to each phase.     

Phase equilibria in the Al---Cr system

The Al---Cr system has been reviewed for Cr content up to 40 at.%. In this system several intermetallic compounds are formed by peritectic reactions. From the temperature of transformation and the composition of the phases, the nature of the invariant transformations is discussed. Transmission electron microscopy studies were performed on samples forming these compounds. A detailed structural interpretation is given for the phase θ-Al₇Cr. A new structure is proposed for Al₄Cr similar to that of the μ-Al₄Mn phase of which the crystal structure is known. The phase Al₅Cr (or Al₁₁Cr₂) was found to be orthorhombic and not monoclinic, as had been previously proposed. The existence of a cubic structure for the Al₉Cr₄ phase was confirmed.

On account of previous results, we should point out that the phases θ-Al₇Cr, Al₄Cr and Al₅Cr present characteristic features of pseudoicosahedral symmetry of the Al₄Cr icosahedral phase: it has been verified in the case of θ and μ that the same type of atomic cluster may be considered in order to describe these structures, i.e. 12 atoms located at the vertices of deformed icosahedra (either 12Al or 11Al + 1Cr or 10Al + 2Cr) whose centres are occupied by a Cr atom.

The reason for such an investigation originated from a study of the Al---Cr---Ni system for which the observed ternary structures appeared incoherent with those given for the binary Al---Cr system. This second study will be reported elsewhere.     

Ti43.5Ni47.0Nb9.0Zr0.5合金的相变和记忆功能

通过示差扫描量热仪、扫描电镜和电子试验机研究Ti43.5Ni47.0Nb9.0Zr0.5丝的相变、显微组织和记忆功能.结果表明:热拉态Ti43.5Ni47.0Nb9.0Zr0.5丝在室温至170 ℃的温度范围内观察不到相变发生,在750 ℃退火时,Ms点和As点分别为-107 ℃和-12 ℃;随着变形量的增加,逆马氏体相变温度大幅度升高,相变热滞变宽;当变形量为13%时,恢复应力达到最大值,为682 MPa,此时恢复应变为6.3%;恢复应力松弛曲线显示Ti43.5Ni47.0Nb9.0Zr0.5丝达到最大恢复应力后随温度的降低,恢复应力下降,在-20～-30 ℃范围内,恢复应力降至300 MPa以下.     

Phase equilibria in the cobalt oxide-copper oxide system

Thermodynamic properties were determined for the system cobalt oxide-copper oxide by means of an electromotive force (EMF) measurement techniques using galvanic cells with calciastabilized zirconia (CSZ) as the solid electrolyte and with air as the reference electrode according to the following schemes: CuO, Cu₂O | CSZ | air and CoO-CuO, Cu₂O CSZ | air for composition variables y=X_Cu/(X_Co+X_cu equal to 0.05, 0.15, 0.25, 0.35, 0.45, 0.667, and 0.8; and within the temperature interval 1200–1350 K. Thermodynamic properties calculated directly from EMF values were combined with the available literature data on phase equilibria, and thermodynamic properties of solid phases in the Co-Cu-O system were assessed. Both terminal solid solutions, (Co,Cu)O and (Cu,Co)O, were described by a sublattice model with Redlich-Kister excess term. The interaction parameters for both (Co,Cu)O and (Cu,Co)O solid solutions and the Gibbs energy of formation for the intermediate phase Cu₂CoO₃ were obtained. The Gibbs energies of fictive end-members: monoclinic “CoO” and “CuO” with rock salt structure were derived as well. The phase diagrams were calculated using the assessed thermodynamic parameters. The (T, y) phase diagram was calculated for existence under ambient air. The property diagrams log₁₀P(O₂) versus composition and activity of CuO versus composition were calculated at 1273 K. The results of our calculations were in a good agreement with available experimental data.     

Phase equilibria in the Co-rich Co-Al-W-Ti quaternary system

We determined phase equilibria in the Co-rich Co-Al-W-Ti quaternary system at a temperature range between 900 °C and 1200 °C with a close attention to the thermodynamic stability of the γ′-Co₃(Al, W, Ti) (L1₂) phase, based on micro-structure observation and electron microprobe analysis on bulk alloy samples heat-treated for periods up to 2000 h. In the quaternary system the single phase field of γ′ extends from the Co-Ti binary edge to a composition of Co-5Al-8.5W-8Ti (in at.%) at 900 °C. At the tip of the single phase field, the γ′ phase is in equilibrium with the γ-Co (A1), Co₂AlTi (L2₁) and Co₃W (D0₁₉) phases. The constructed vertical section of phase diagram between Co-9.4Al-9.6W and Co-16.5Ti indicates that there is a narrow composition range around Co-4.5Al-5.4W-7.5Ti in which the γ single phase field exists at high temperatures above 1200 °C and two-phase of γ+γ′ is thermodynamically stable at low temperatures below 1100 °C.     

Phase equilibria in the cobalt oxide-copper oxide system

Thermodynamic properties were determined for the system cobalt oxide-copper oxide by means of an electromotive force (EMF) measurement techniques using galvanic cells with calciastabilized zirconia (CSZ) as the solid electrolyte and with air as the reference electrode according to the following schemes: CuO, Cu₂O | CSZ | air and CoO-CuO, Cu₂O CSZ | air for composition variables y=X_Cu/(X_Co+X_cu equal to 0.05, 0.15, 0.25, 0.35, 0.45, 0.667, and 0.8; and within the temperature interval 1200–1350 K. Thermodynamic properties calculated directly from EMF values were combined with the available literature data on phase equilibria, and thermodynamic properties of solid phases in the Co-Cu-O system were assessed. Both terminal solid solutions, (Co,Cu)O and (Cu,Co)O, were described by a sublattice model with Redlich-Kister excess term. The interaction parameters for both (Co,Cu)O and (Cu,Co)O solid solutions and the Gibbs energy of formation for the intermediate phase Cu₂CoO₃ were obtained. The Gibbs energies of fictive end-members: monoclinic “CoO” and “CuO” with rock salt structure were derived as well. The phase diagrams were calculated using the assessed thermodynamic parameters. The (T, y) phase diagram was calculated for existence under ambient air. The property diagrams log₁₀P(O₂) versus composition and activity of CuO versus composition were calculated at 1273 K. The results of our calculations were in a good agreement with available experimental data. This paper was presented at CALPHAD XXX International Conference on Phase Diagram Calculations in York, UK, May 27–June 1, 2001, and appeared in the Conference Abstracts on Page 75.     

Phase transformation behavior of Ti49Ni49.5Fe1V0.5 and Ti48Ni48.5Fe1V2.5 alloys after different heat treatments简

The effects of heat treatments on the phase transformation behavior of Ti49 Ni49.5 Fe1 V0.5 and Ti48 Ni48.5 Fe1 V2.5 alloys were investigated. The results indicate that the alloys subjected to different heat treatments have B2 structure at room temperature. All the specimens exhibit a twostage B2→R→B190martensitic transformation on cooling, but a B190→B2 one-stage reverse martensitic transformation on heating except aged A1 alloy, which undergoes an abnormal two-stage transformation upon heating. The phase transformation temperatures are affected by heat treatments and V content, which can be attributed to the variation of the second-phase particles content in the matrix.     

Phase equilibria and structural investigations of the general NiAs-type in the ternary system Ni–Sn–Te

The ternary system Ni–Sn–Te was investigated by means of light optical microscopy (LOM), powder X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDX). Two isothermal sections at 600 and 800 °C were investigated experimentally. The two ternary compounds, Ni_5.78SnTe₂ (space group I4/mmm, Pearson symbol tI18) and Ni_3−xSnTe₂ (space group P6₃/mmc, Pearson symbol hP12), already known from literature, were confirmed, although Ni_3−xSnTe₂ was found only at 600 °C. At higher temperatures a continuous phase field of the general NiAs-type structure was discovered between NiTe_2−x and Ni₃Sn₂ HT. It ranges continuously from 34 to 63 at.% Ni, covering CdI₂-types, as well as Ni₂In-type domains; thus a continuous transition from the CdI₂ to Ni₂In type is confirmed, to the best of our knowledge, for the first time. Lattice parameter variations and the transition CdI₂–NiAs–Ni₂In in the ternary phase field were analysed.Furthermore, vertical sections at 10, 40, 55, 60 and 70 at.% Ni were determined. A liquidus surface projection and a reaction scheme of the system were constructed as well. Altogether, 17 invariant phase reactions, including 3 eutectic reactions, 2 peritectic reactions, 11 transition reactions and one maximum were discovered.