Fe-Zr System Research Articles

A Nonconventional Method to Produce Zr Alloys to Study the Fe23Zr6 Intermetallic Compound in the Fe-Zr System

A Nonconventional Method to Produce Zr Alloys to Study the Fe23Zr6 Intermetallic Compound in the Fe-Zr System

Experimental investigation and thermodynamic evaluation of the C–Fe–Zr ternary system

Phase relations in the C–Fe–Zr ternary system were investigated using the experimental data obtained through the combination of X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) techniques. Isothermal sections of the C–Fe–Zr system were experimentally determined at 1173 K, 1273 K, 1373 K, and 1473 K, and no ternary compound was found in this system. A self-consistent set of thermodynamic parameters of the C–Fe–Zr system were obtained for the first time using the CALculation of PHAse Diagram (CALPHAD) method, and the calculated results showed good consistency with the experimental data. It can provide reliable thermodynamic information of molten corium composition as one of necessary subsystems.

Experimental and thermodynamic study of high-temperature phase stability of Fe–Zr binary alloy

This work investigated the high-temperature phase stability of Fe–Zr binary alloy using the CALPHAD approach combined with an experimental study. The controversial Fe23Zr6 phase in the Fe–Zr system was recognized as a stable phase by annealing at 1273 K for 1440 h, followed by X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. The conditions affecting the stability of the Fe23Zr6 phase, such as the cooling rate, annealing time, and atmosphere, were investigated. The experimental results indicated that the Fe23Zr6 phase precipitates more under longer annealing time and faster cooling rate, and the phase is not oxygen stabilized. The liquidus temperature from the Fe2Zr_C15 phase to the Zr end region was measured using high temperature differential scanning calorimetry. A combination of the experimental results and the findings in recent literature enabled us to reoptimize the Fe–Zr system using the CALPHAD approach.

Phase stability of Fe23Zr6 and thermodynamic reassessment of Fe–Zr system

The stability of the Fe23Zr6 phase in Fe–Zr system was studied, and the partial Fe–Zr phase diagram was revised by means of X-ray diffraction, electron probe microanalysis and differential thermal analysis methods. On the basis of the experimental results in the present work and literature, the Fe–Zr system was reassessed using CALculation of PHAse Diagram (CALPHAD) method. Solution phases, liquid, fcc, bcc and hcp, are modeled as the substitutional solution. The intermetallic compounds, hex.-Fe2Zr, Fe2Zr, FeZr2 and FeZr3 phases, are treated as Fe2(Fe, Zr)1, (Fe, Zr)2(Fe, Zr)1, (Fe, Zr)1Zr2 and (Fe, Zr)1(Fe, Zr)3 by a two-sublattice model, respectively. The Fe23Zr6 phase is treated as stoichiometric compound. A set of self-consistent thermodynamic parameters of the Fe–Zr system was obtained. The results confirm the stability of Fe23Zr6 phase, improve the phase diagram of the Fe–Zr system and provide a theoretical reference for the development of Zr alloys.

Thermodynamic Descriptions of the Co–Zr and Co–Fe–Zr Systems

The Co–Fe–Zr system and its Co–Zr subsystem were optimized using the CALculation of PHAse Diagram (CALPHAD) approach. The substitutional solution model was used for describing the phases liquid, fcc_A1, bcc_A2 and hcp_A3. Two Laves phases were modeled as (Co,Fe,Zr)2(Co,Fe,Zr)1, and the phases CoFe and CoZr with the bcc_B2 crystal structure were described as the ordered one of bcc_A2 in the formula (Co,Fe,Va,Zr)0.5(Co,Fe,Va,Zr)0.5Va3. With limited solubility ranges, all other phases were treated as the line compounds (Co,Fe)mZrn. An excellent agreement between the reported and calculated results was reached. The reliable thermodynamic parameters of the Co–Fe–Zr system were acquired, which can be well applied to various thermodynamic calculations and materials design.

Production of Permanent Magnets for Magnetically Hard Alloys Using Rare-Earth Metals

A requirement for improving powder metallurgy technology of alloys for permanent magnets containing rare-earth metals based on the use of secondary resources and a replacement of rare-earth metals and fine control of the semifinished products chemical composition is demonstrated. These approaches are realized successfully in the preparation of Nd–Fe–B system magnetically hard materials by a binary mixture method using rare earth metal hydrides and their alloys. Analysis of the magnetic properties of Sm–Co–Cu–Fe–Zr system permanent magnets according to the results of the primary ingot chemical composition control minimizes production costs.

Heat capacity measurement of Zr2Fe and thermodynamic re-assessment of the Fe–Zr system

Critical evaluation of the Fe–Zr binary system has been performed based on the available experimental and calculated data. New experimental data on the heat capacity of Zr2Fe have been obtained using differential scanning calorimetry. Thermodynamic parameters have been optimized using the CALPHAD approach. New experimental results of specific heat capacity and ab-initio calculations for the ZrFe2, Zr2Fe and Zr3Fe intermetallic compounds have been taken into account in the optimization of the thermodynamic parameters. A self-consistent thermodynamic description of the Fe–Zr system has been obtained. Using the generalized “χ2”–criterion, the results calculated using the thermodynamic descriptions derived in the present work are compared with those previously published.

Initiation of the Explosive Crystallization Process in Amorphous Alloys of the Fe-Zr System by Pulse Laser Treatment

Initiation of the Explosive Crystallization Process in Amorphous Alloys of the Fe-Zr System by Pulse Laser Treatment

Investigation of microstructure and fracture toughness of Fe-Zr welded joints

In this work, the mechanical properties of Fe-Zr welded joints and its dependence with the microstructures were investigated using nanoindentation. In the weld metal, Fe2Zr intermetallic phase was observed and its average hardness and fracture toughness are 19.3 GPa and 2.52 MPam1/2, respectively. It was noticed that radial cracks initiated from the corners of the impressions. Fine lamellar structure (αFe + Fe2Zr) with an average hardness of 7.5 GPa were observed but no cracks were observed when subjected to a peak load of 300 mN. A simple model was developed to explain possible phase formation mechanism in the Fe-Zr system.

Grain size stabilization of mechanically alloyed nanocrystalline Fe-Zr alloys by forming highly dispersed coherent Fe-Zr-O nanoclusters

Grain size stabilization is crucial for the production and application of nanocrystalline (NC) materials. The mechanically alloyed (MA) NC Fe-Zr system is known as a very successful NC system as it exhibits excellent thermal stability at elevated temperatures. The grain size stabilization of this system has been previously ascribed to its reduced grain boundary (GB) energy by Zr segregation and Zener pinning of Zr-rich intermetallic precipitates. In this work, we report a different mechanism that significantly contributes to grain size stabilization of this NC alloy system using two MA-produced NC Fe-Zr alloys (Fe-1 at.% Zr and Fe-5 at.% Zr) as examples. We show by using atom probe tomography and Cs-corrected transmission electron microscopy that highly dispersed coherent Fe-Zr-O nanoclusters, with a number density up to 1024 m−3, form in ferrite matrix after annealing at certain temperatures. Our first-principles calculations indicate that the formation of these nanoclusters is caused by the ordering of Zr and O-impurity in ferrite matrix. We analyzed the underlying mechanism of grain size stabilization in terms of the experimental results and the Zener pinning theory, and suggest that the pinning effect exerted by these nanoclusters significantly contributes to grain size stabilization of the NC Fe-Zr alloys.

Thermodynamic investigation of the Zr-Fe-Nb system and its applications

The total energies and enthalpies of intermetallic compounds, such as the Laves phases, Fe23Zr6 and τ1, in the Zr-Fe-Nb system have been studied by using the first-principles pseudo-potential VASP code with a full relaxation of all structural parameters. Based on the calculation results and recent experimental information, a new thermodynamic description of the Fe-Zr binary system has been established using the CALPHAD approach. The controversial intermetallic phase Fe23Zr6 in the Fe-Zr system was treated as a stable phase and the high-temperature Laves C36 phase was excluded from equilibrium. However, the first-principles calculations show that the Fe23Zr6 phase is not stable at 0 K implying a transition from metastable to stable Fe23Zr6 at certain temperature, i.e. 225 K predicted by the present work. The thermodynamic description of Fe-Nb system has been revised to better fit the experimental data for the Laves C14 phase boundary. The thermodynamic description of the Zr-Fe-Nb system has been developed based on the first-principles calculations and available experimental data. With the present modeling, the phase transition temperatures, phase relations and properties of intermetallic precipitates can be predicted in order to plan heat treatments and rolling process for zirconium alloys. The phase contents of Zr-2.6Nb-0.03Fe and Zr-1.0Nb-1.8Fe (wt.%) versus temperature are presented as a practical example for application.

Thermodynamic description of hydrogen storage materials Cr–Ti–Zr and Fe–Ti–Zr

Abstract

Теоретична аналіза процесів фазоутворення в аморфних стопах системи Fe—Zr

Теоретична аналіза процесів фазоутворення в аморфних стопах системи Fe—Zr

Characterization of solidified melt among materials of UO2 fuel and B4C control blade

To predict the fundamental phase relationships in the solidified core melt of the Fukushima Daiichi Nuclear Power Plant, solidified melt samples of the various core materials [B4C, stainless steel, Zr, ZrO2, (U,Zr)O2] were prepared by arc melting. Phases and compositions in the samples were determined by means of X-ray diffraction, microscopy, and elemental analysis. With various compositions, the only oxide phase formed was (U,Zr)O2. After annealing, the stable metallic phases were an Fe-Cr-Ni alloy and an Fe2Zr-type (Fe,Cr,Ni)2(Zr,U) intermetallic compound. The borides, ZrB2 and Fe2B-type (Fe,Cr,Ni)2B, were solidified in the metallic part. Annealing at 1773 K under an oxidizing atmosphere (Ar-0.1%O2) resulted in the oxidation of U and Zr in the alloy and in ZrB2, and consequently the (Fe,Cr,Ni)2B and Fe-Cr-Ni alloy became dominant in the metallic part. The experimental phase relationships in the metallic part agreed reasonably with the thermodynamic evaluation of equilibrium phases in a simplified B4C–Fe–Zr system. The metallic Zr content in the melt was found to be a key factor in determining the phase relationships. As a basic mechanical property, the microhardness of each phase was measured. The borides, especially ZrB2, showed notably higher hardness than any other oxide or metallic phases.

Thermodynamic modeling and experimental study of the Fe–Cr–Zr system

This work developed thermodynamic models for describing phase stability and thermodynamic property of the Fe–Cr–Zr system using the Calphad approach coupled with experimental study. Thermodynamic descriptions of the Fe–Cr and Cr–Zr systems were either directly adopted or slightly modified from literature. The Fe–Zr system has been remodeled to accommodate recent ab-initio calculation of formation enthalpies of various Fe–Zr compounds. Reliable ternary experimental data and thermodynamic models were mainly available in the Zr-rich region. Therefore, selected ternary alloys located in the vicinity of the eutectic valley of β(Fe,Cr,Zr) and (Fe,Cr)2Zr laves phase in the Fe-rich region have been experimentally investigated in this study. Microstructure has been examined by using scanning electron microscope, energy-dispersive X-ray spectroscopy and X-ray diffraction. These experimental results, along with the literature data were then used to develop thermodynamic models for phases in the Fe–Cr–Zr system. Calculated phase equilibria and thermodynamic properties of the ternary system yield satisfactory agreements with available experimental data.

Thermodynamic assessment of the Fe–Al–Zr phase diagram

The thermodynamic assessment of the Fe–Al–Zr ternary system was performed using the CALPHAD technique. The four published isothermal sections at 1073, 1173, 1273 and 1423 K, together with the proposed liquidus surface and the corresponding invariant reaction scheme, were taken into account. The reliability of the previous binary assessments was checked for the systems of interest, namely, for the Fe–Zr, Zr–Al and Fe–Al systems. Reassessment of the C15 Laves phase of the Fe–Zr system has been done to obtain a better description of the phases in the ternary system. The solution phases, including liquid, α -Fe, γ -Fe, α -Zr, β -Zr and γ -Al, were modelled as substitutional solutions, while the new ternary phases ( τ 1 , τ 2 and τ 3 ) were modelled as linear and stoichiometric compounds, respectively. The C14 and C15 Laves phases have been assessed using a two-sublattice model. Any ternary solubility of the other binary phases was not taken into account in the ternary assessment. The liquidus projection and several isothermal sections were calculated, and they agreed reasonably well with the reported experimental data.

Magnetic behavior of cosputtered Fe-Zr amorphous thin films exhibiting perpendicular magnetic anisotropy

Excellent mechanical properties of amorphous or glassy metals along with the capability to fabricate sub-50-nm patterns promise their application as a futuristic material for production of various nano- or microelectromechanical systems. In addition to their applications, these materials pose a lot of challenges in understanding their fundamental properties because of their random structure and involvement of three or more different kinds of atoms. The amorphous Fe-Zr system which is reported to exhibit superconductivity, ferromagnetism, spin glass, and antiferromagnetism is an ideal system to understand. The controversial magnetic properties of this system are still a subject of debate. In the present paper we revisited Fe-Zr system and studied their detailed magnetic properties in the temperature range of 5--330 K. ${\text{Fe}}_{x}{\text{Zr}}_{100\ensuremath{-}x}$ ($x=63$, 68, 76, 86, 92, and $93\text{ }\text{at}\text{.}\text{ }%$) thin films were deposited on silicon (100) substrate by a cosputtering technique. The Curie temperature $({T}_{c})$ is shown to increase almost linearly with an increase in Fe concentration, but it decreases rapidly for the Fe-rich films. The films with $x$ up to $\ensuremath{\sim}86\text{ }\text{at}.\text{ }%$ have a strange shape of the hysteresis loop and are shown to exhibit perpendicular magnetic anisotropy with a stripe domain structure. Hysteresis loop shapes are correlated with the magnetic structure of the films, and provide an easy understanding of magnetic properties. It has been shown that the Fe-rich films are composed of antiferromagnetic Fe clusters which are embedded in the ferromagnetic amorphous FeZr.

Thermodynamic description of the Al–Fe–Zr system

The Fe–Zr and Al–Fe–Zr systems were critically assessed by means of the CALPHAD technique. The solution phases, liquid, face-centered cubic, body-centered cubic and hexagonal close-packed, were described by the substitutional solution model. The compounds with homogeneity ranges, hex.- Fe 2Zr, Fe 2Zr, FeZr 2 and FeZr 3 in the Fe–Zr system, were described by the two-sublattice model in formulas such as hex.- Fe 2(Fe,Zr), (Fe,Zr) 2(Fe,Zr), (Fe,Zr)Zr 2 and (Fe,Zr)(Fe,Zr) 3 respectively. The compounds Al m Zr n except Al 2Zr in the Al–Zr system were treated as line compounds (Al,Fe) m Zr n in the Al–Fe–Zr system. The compounds FeZr 2 and FeZr 3 in the Fe–Zr system were treated as (Al,Fe,Zr)Zr 2 and (Al,Fe,Zr)(Fe,Zr) 3 in the Al–Fe–Zr system, respectively. All compounds in the Al–Fe system and hex.- Fe 2Zr in the Fe–Zr system have no solubilities of the third components Zr or Al, respectively, in the Al–Fe–Zr system. The ternary compounds λ 1 with C14 structure and λ 2 with C15 structure in the Al–Fe–Zr system were treated as λ 1 - (Al,Fe,Zr) 2(Fe,Zr) with Al 2Zr in the Al–Zr system and λ 2 - (Al,Fe,Zr) 2(Fe,Zr) with Fe 2Zr in the Fe–Zr system, respectively. And the ternary compounds τ 1 , τ 2 and τ 3 in the Al–Fe–Zr system were treated as (Al,Fe) 12Zr, Fe(Al,Zr) 2Zr 6 and Fe 7Al 67Zr 26, respectively. A set of self-consistent thermodynamic parameters of the Al–Fe–Zr system was obtained.

10.1007/s11508-008-2009-1

The lamellar Fe-Zr systems obtained by the method of ion-plasma sputtering deposition have been studied by Mossbauer spectroscopy and X-ray diffraction phase analysis. These systems were subjected to sequential isochronous annealings in a temperature range of 400–1100°C and sequential isothermal annealings at 900°C. The sequence of the phase transformations has been established. The relative content of the phases that are formed in the bulk of the sample at each stage of annealing has been found. It has been shown that the trend of the phase transformations in the sample is determined by changes in the local concentrations of its components in the process of their mutual diffusion. The process of thermal stabilization in the lamellar Fe-Zr system has been realized upon isothermal annealing.

High temperature mass spectrometry: Application to the thermodynamic study of the Fe–Zr system

The high temperature mass spectrometry method is a standard method for the study of chemical equilibria at high temperature. For our studies of complex nuclear materials, the multiple Knudsen cell is the most promising device to perform thermodynamic activity measurements. We illustrate it with some new results obtained about the iron–zirconium system.