Fe Binary System Research Articles

Crystal structure of AlFe0.95.

Three B2-type inter-metallic AlFe1 - δ phases (0.18 < δ < 0.05) in the Al-Fe binary system were synthesized by smelting and high temperature sinter-ing methods. The exact crystal structure for δ = 0.05 was refined by single-crystal X-ray diffraction. The amount of vacancy defects at the Fe atom sites was obtained by refining the corresponding site occupancy factor, converging to the chemical formula AlFe0.95, with a structure identical to that of ideal AlFe models inferred from powder X-ray or neutron diffraction patterns.

Mechanism of reduction-diffusion reaction in Sm–Fe binary system at low temperature using molten salts

In this study, the mechanism of the reduction-diffusion reaction in a Sm–Fe binary system at low temperature was studied to investigate the possibility of synthesis of a Fe-rich TbCu7-type SmFex (x > 9) by the low-temperature diffusion-reduction (LTRD) process using LiCl–KCl eutectic molten salts. Firstly, the Sm–Fe phase transformation depending on the Sm–Fe composition, the LTRD temperature, and time was investigated, and it is found that the obtained metastable phase is only TbCu7-type SmFe∼8.5, which is not a Fe-rich phase. This Fe content does not change even after an expended LTRD process, and the metastable TbCu7-type SmFe∼8.5 tends to transform to the stable Sm2Fe17 phase. In addition, it is found that the Sm–Fe phase starts to synthesize from the Sm-rich phase in the order of SmFe2, SmFe3, and SmFe8.5 as the LTRD temperature increases (when the time was 10 h) or the LTRD time increases (when the temperature was 550 °C). Core-shell-like particles are observed in the case of a short LTRD time, and the core and the shell are Fe and the Sm-rich Sm–Fe phase, respectively, indicating that the Sm-rich phase begins to produce on the surface of the Fe particles. It is difficult to synthesize a Fe-rich TbCu7-type SmFex (x > 9) phase with the Sm–Fe binary system, suggesting that a different approach, such as addition of other elements, will be necessary.

The Mineralogy of Pt-Fe alloys and phase relations in the Pt–Fe binary system

ABSTRACT A revised Pt–Fe phase diagram is proposed to replace those used in the materials science literature (e.g., Okamoto 2004), and to improve the one of Cabri &amp; Feather (1975) by adding high-temperature phase equilibria data published in the mineralogical literature. The projected solid-solution fields at room temperature in the pure Pt–Fe system lie at the following approximate compositions: for γ(Pt,Fe) from Pt to Pt0.78Fe0.22, for Pt3Fe from Pt3.04Fe0.96 to Pt2.64Fe1.36, for PtFe from Pt1.16Fe0.84 to Pt0.67Fe0.33, and for PtFe3 from Pt1.26Fe2.94 to Pt0.68Fe3.32. The phase relations and phase boundaries are discussed and evaluated for Pt-Fe alloys occurring in pristine intrusive rocks and ores as well as in eluvial and placer deposits derived from the former by physical and chemical weathering over long periods of geologic time. In spite of the variable concentrations of minor and trace elements, the natural Pt-Fe alloy minerals correlate well with phase relations in the pure Pt–Fe binary system.

Experimental study, first-principles calculation and thermodynamic modelling of the Cr–Fe–Nb–Sn–Zr quinary system for application as cladding materials in nuclear reactors.

This paper is dedicated to the Calphad modelling of the Cr–Fe–Nb–Sn–Zr quinary system. In previous papers, the thermodynamic modelling of the Cr–Nb–Sn–Zr quaternary system, the Fe–Sn–Zr and Fe–Nb–Zr ternary systems as well as the Fe–Nb binary system were carried out. Since no experimental data were available for the Cr–Fe–Sn and Fe–Nb–Sn ternary systems, new partial isothermal sections have been measured at 1073K and 973K, respectively. In addition to these experimental data, Density Functional Theory (DFT) calculations are performed in order to determine formation enthalpies of the stable and metastable ordered compounds. At last, the Special Quasirandom Structures (SQS) method is used together with DFT calculations in order to calculate the mixing enthalpy of the A2 (bcc) binary solid solution. Finally, these experimental and calculated data are jointly used with those from the literature as input data for the Calphad modelling of the Cr–Fe binary system as well as the Cr–Fe–Nb, Cr–Fe–Sn, Cr–Fe–Zr and Fe–Nb–Sn ternary systems. The ternary systems are then combined into a quinary database for which application examples are provided.

Experimental determination of phase diagram at 450 °C in the Zn–Fe–Al ternary system

Phase equilibria in multi-phase Zn–Fe–Al alloys were experimentally measured using a field-emission electron probe micro-analyzer for alloy samples, and a precise iso-thermal phase diagram at 450 °C in the entire composition range of the Zn–Fe–Al ternary system, except for the Fe-rich corner, was determined. The ternary solubility ranges of the Γ-Fe4Zn9, Γ1-Fe21.2Zn80.8, δ1k-FeZn7, and ζ-FeZn13 on the Fe–Zn side and of the ζ-FeAl2, η-Fe2Al5, and θ-Fe4Al13 on the Fe–Al side were consistent with the latest corresponding binary data, whereas no δ1p-Fe13Zn126 phase was detected. The single-phase region of the Γ2-Fe8Zn87Al4 ternary intermetallic compound phase is significantly narrower than that reported in the previous studies. The solubility of Fe in the liquid phase increased consistently and continuously from the value in the Zn–Fe binary system (0.6 at.%) up to 1.2 at.% at 31 at.% Al with increasing Al content. In the Al-rich portion of the phase diagram at 450 °C, the Fe(Al, Zn)6 intermetallic compound phase was newly discovered, and confirmed to be an isomorph extended from the FeAl6 phase which is metastable in the Fe–Al binary system.

Graphitic‐Shell Encapsulation of Metal Electrocatalysts for Oxygen Evolution, Oxygen Reduction, and Hydrogen Evolution in Alkaline Solution

AbstractDeveloping highly efficient, cost effective, and environmentally friendly electrocatalysts for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) is of interest for sustainable and clean energy technologies, including metal–air batteries and fuel cells. In this work, the screening of electrocatalytic activities of a series of single metallic iron, cobalt, and nickel nanoparticles and their binary and ternary alloys encapsulated in a graphitic carbon shell toward the OER, ORR, and HER in alkaline media is reported. Synthesis of these compounds proceeds by a two‐step sol–gel and carbothermal reduction procedure. Various ex situ characterizations show that with harsh electrochemical activation, the graphitic shell undergoes an electrochemical exfoliation. The modified electronic properties of the remaining graphene layers prevent their exfoliation, protect the bulk of the metallic cores, and participate in the electrocatalysis. The amount of near‐surface, higher‐oxidation‐state metals in the as‐prepared samples increases with electrochemical cycling, indicating that some metallic nanoparticles are not adequately encased within the graphite shell. Such surface oxide species provide secondary active sites for the electrocatalytic activities. The Ni–Fe binary system gives the most promising results for the OER, and the Co–Fe binary system shows the most promise for the ORR and HER.

Micro-Vickers Hardness of Intermetallic Compounds in the Zn-rich Portion of Zn–Fe Binary System

Micro-Vickers Hardness of Intermetallic Compounds in the Zn-rich Portion of Zn–Fe Binary System

Experimental determination of phase equilibria of Al-rich portion in the Al–Fe binary system

Al-rich portion of the Al–Fe binary phase diagram was determined by conventional heat-treatment for equilibration, the diffusion couple method and thermal analysis. Equilibrium compositions are mostly coincident with the generally accepted phase diagram in the literature up to 1000 °C, except the solubility range of θ-Fe4Al13 phase. The solubility ranges of the η-Fe2Al5 and the θ-Fe4Al13 phases were confirmed to increase and incline to the Fe-rich side with increasing temperature. Phase boundaries and the eutectoid composition of the ε-Fe5Al8 phase were determined from the diffusion couple method and heating curves of DSC measurement, which were slightly shifted to a higher Fe concentration. Transformation temperatures of liquidus, solidus and invariant reactions determined from heating curves of DSC measurement were mostly lower than those in the phase diagram evaluated by Kattner and Burton. An invariant reaction related to the formation of the θ-Fe4Al13 phase was confirmed as the peritectic reaction of Liquid + η-Fe2Al5 = θ-Fe4Al13 in this study taking equilibrium compositions of the η-Fe2Al5 + θ-Fe4Al13 phases and solidus temperatures of the θ-Fe4Al13 phase into consideration.

1:13 phase formation mechanism and first-order magnetic transition strengthening characteristics in (La,Ce)Fe13–x Si x alloys

The effects of the introduction of Ce to La1−xCexFe11.5Si1.5 alloys on 1:13 phase formation mechanism, the first-order magnetic phase transition strengthening characteristics, and magnetocaloric property were studied, respectively. The results show that the formation mechanisms of 1:13 and LaFeSi phases in La1−xCexFe11.5Si1.5 alloys are the same as those of Ce2Fe17 and CeFe2 phases in Ce–Fe binary system, respectively. The substitution of Ce in 1:13 phase which is limited can make the first-order magnetic phase transition characteristics strengthen, which can make thermal and magnetic hysteresis increase, the temperature interval of temperature-induced phase transition decrease, and the critical magnetic field of field-induced magnetic phase transition (HC) increase, respectively. Owing to the lattice shrink of 1:13 phase with the increase in Ce content, the Curie temperatures (TC) show a linear decrease. The maximum change in magnetic entropy gradually increases due to the decrease in temperature interval of temperature-induced phase transition, but the relative cooling capacities are all about 80 J·kg−1 at magnetic field of 2 T.

Thermodynamic measurement of Dy + Fe binary system by double Knudsen cell mass spectrometry

The activities of Dy in Dy–Fe alloys with Dy concentrations ranging from (7.0 to 89)at% were determined at (1273 to 1573)K by measuring the ion current of the vapor of Dy in equilibrium with Dy–Fe melts, Dy2Fe17+γFe, etc. The standard Gibbs energy of formation of Dy2Fe17, Dy6Fe23, DyFe3, and DyFe2 were calculated from the activities of Dy obtained from these measurements.

Reactions between U–Zr alloys and Fe at 1003 K

In metal fuel for fast reactors, liquefaction at the fuel–cladding interface may occur in off-normal events and enhance cladding wastage. To provide the basis for understanding this liquefaction phenomenon, reactions in diffusion couples of U–23at.%Zr alloys and Fe at 1003K have been examined. The selected temperature is 5K higher than the eutectic point in the U–Fe binary system. The effect of lanthanide fission products on the liquefaction was evaluated by adding 1at.%Ce to some of the U–Zr specimens. The test results indicated that a liquid phase formed in the reaction zone. The phases in the reaction zone were identified based on electron probe microanalysis results and the calculated U–Zr–Fe phase diagram. The reaction zone growth rate decreased with time. The thickness of the reaction zones at 1003K in diffusion couples pre-annealed at 923K was less than those in diffusion couples without the pre-anneal. Zirconium in the fuel alloy has little influence on the threshold temperature for the liquefaction onset, and the addition of 1at.%Ce has little effect on the reaction of U–Zr alloy with Fe.

Self-ignition combustion synthesis of TiFe in hydrogen atmosphere

This paper describes the self-ignition combustion synthesis (SICS) of highly active titanium iron (TiFe) in a high-pressure hydrogen atmosphere without employing an activation process. In the experiments, well-mixed powders of Ti and Fe in the molar ratio of 1:1 were uniformly heated up to 1085 °C, the eutectic temperature of Ti–Fe binary system, in pressurized hydrogen at 0.9 MPa. The electric source was disconnected immediately after the ignition between Ti and Fe, and the mixture was cooled naturally. In this study, the exothermic reaction Ti + Fe = TiFe + 40 kJ occurred at around 1085 °C after the hydrogenation and decomposition of Ti. X-ray diffraction analysis showed that the final product had only one phase—TiFeH 0.06—which can store hydrogen of 1.55 mass% under hydrogen pressure of 4 MPa. The product obtained by SICS contained considerably more hydrogen quickly as compared to the commercially available product; this fact can be explained by the porous structure of the obtained product, which was observed using a scanning electron microscope. In conclusion, the SICS of TiFe saved time and energy, yields products with high porosity and small crystals, enabled easy hydrogenation, and did not require activation processes.

Novel rotation-cylinder method for the processing of binary alloys with no range of solid solubility

The Ag–Fe binary system is of commercial importance for providing electrical contact materials replacing cancerous Cd-bearing Ag-CdO. Until now, however, Ag–Fe contact materials can only be manufactured by powder metallurgy, simply because there is no range of solid solubility of Fe in Ag. The purpose of this study is to develop a cost-effective molten-metal process for the production Ag–Fe binary contact materials based on a rotation-cylinder method (RCM), in terms of replacing cancerous Ag-CdO as well as reducing material cost and process cost. The present study includes RCM for alloying Ag and Fe, subsequent extrusion and drawing procedures, manufacturing step for solid-type and clad-type electrical contacts and finally mechanical properties of them.

Thermodynamic optimization of the B–Fe system

The B–Fe binary system has been optimized using the CALPHAD method, utilizing published experimental thermochemical and phase diagram data. Two models for the solid solubility of B in b.c.c. Fe and in f.c.c. Fe are presented, B as a interstitial, and B as a substitutional constituent. Thermodynamic calculations based on the interstitial and the substitutional model were in good agreement with experimental data.

メカニカルアロイングによるＡｌ９０−ｘＦｅｘＣｒ１０系アモルファス相およびナノ結晶体の生成

Pure elemental powders of Al, Fe and Cr corresponding to the compositions of Al90–xFexCr10 (x= 10, 25, 50) were mechanically alloyed by high-energy ball mill using a ball-to-powder weight ratio of 250:10. The structural evolution in these alloys was investigated by X-ray diffraction and transmission electron microscopy. Additionally, thermal stability of the mechanically-alloyed powders was tested by DSG. Amorphous phase was partially formed in Al65 Fe25Cr10 and Al4OFe50Cr10 mechanically-alloyed powders at the early stage of milling. Al5(Fe, Cr)2 and Al(Fe, Cr) compounds were formed in the middle stage of milling. In the last milling stage, a mixture of amorphous and nanocrystal was obtained in Al80Fe10Cr10 and Al65Fe25Cr10 mechanically-alloyed powders. Only nanocrystal was observed in Al40Fe50Cr10 mechanically-alloyed powder after long time milling. The crystallization temperature of these amorphous phases is about 150 K higher than that of the amorphous phase in Al–25 at%Fe binary system. It is proposed that the existence of Al–Cr atomic cluster in the amorphous matrix can improve the thermal stability of the amorphous matrix.

Ａｌ‐１％Ｍｇ２Ｓｉ合金の４７３Ｋ時効挙動に及ぼす銅添加の影響の比抵抗法による検討

Al–1%Mg2Si–0, −0.17, −0.43, −0.72%Cu alloys were solution treated for 3.6 ks at 848 K, water quenched and aged at 473 K. Behavior of added Cu during these heat treatments and effect of the Cu on age-hardening were investigated by resistometry and tensile test with assist of transmission electron microscopy. The resistivity in as water quenched state well coincides with the value calculated from 0.023 mass%Fe, the equilibrium solubility at 848 K in Al–Fe binary system, and all of other elements in solution. Moreover, the resistivity increases linearly with amount of the added Cu. Namely all of the added Cu is dissolved in the as quenched state. By Cu addition, the initial age-hardening rate at 473 K aging is increased and the softening with over-aging is suppressed. Though the Cu addition increases proof stress at peak age-hardening, it also decreases the resistivity decrement from the as quenched state caused by the aging. This discrepancy, that the small total amount of precipitates, which is suggested from small decrement of resistivity by the peak aging, gives the larger age-hardening, can be explained by the decrease in average length with Cu addition which may be directly related to the increase in number of needle shaped precipitates per unit area.

Fast amorphization and crystallization in Al–Fe binary system by high-energy ball milling

Large amount of amorphous phase of Al–Fe binary system was obtained by MA of elemental powders using a high-energy ball mill at milling intensity of 150 G ( G is the gravitational acceleration). XRD, HRTEM and DSC were used to analyze the process of amorphization and crystallization. The time required achieving almost complete amorphous state is only 4.2 ks for Al–25 at.%Fe system and 3 ks for Al–30 at.%Fe system, respectively. The time of amorphous formation is very shorter than that of previous reports on Al–Fe binary system. Further milling causes rapid crystallization of the amorphous phase. By analysis of S( Q), the presence of a strong Al–Fe chemical short-range order in the amorphous matrix is suggested. Moreover, the superstructure of these Al–Fe clusters in the amorphous matrix is similar to the solid structure of Al 5Fe 2, and the clusters transform into the nucleus of Al 5Fe 2 intermetallic compound under the action of milling energy.

Investigation of the CeFe binary system

The CeFe binary system was investigated and an FeCe binary phase diagram was proposed. This system consists of 1. (i) two peritectic reactions, γ- Fe + L → Ce 2 Fe 17 and Ce 2 Fe 17 + L → CeFe 2, occurring isothermally at 1063°C and 925°C respectively; 2. (ii) a eutectic reaction, L → CeFe 2 + Ce, occurring isothermally at 592°C with eutectic containing 83.3 at.% Ce (92.6 wt.% Ce); 3. (iii) a peritectoid reaction, γ-Fe + Ce 2Fe 17 → α-Fe(Ce), occurring isothermally at 922 °C. The solid solubility of cerium in iron in the temperature range 850–900 °C was found to be less than 0.04 at.% (0.1 wt.%). The Curie temperature of α-Fe(Ce) was slightly lowered with increasing cerium content in solid solution.