Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

NASA Astrophysics Data System (ADS)

Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

2017-01-01

Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

Melting of Fe and Fe0.9Ni0.1 alloy at high pressures

NASA Astrophysics Data System (ADS)

Zhang, D.; Jackson, J. M.; Zhao, J.; Sturhahn, W.; Alp, E. E.; Hu, M. Y.; Toellner, T.

2014-12-01

Cosmochemical studies suggest that the cores of terrestrial planets are primarily composed of Fe alloyed with about 5 to 10 wt% Ni, plus some light elements (e.g., McDonough and Sun 1995). Thus, the high pressure melting curve of Fe0.9Ni0.1 is considered to be an important reference for characterizing the cores of terrestrial planets. We have determined the melting points of fcc-structured Fe and Fe0.9Ni0.1 up to 86 GPa using an in-situ method that monitors the atomic dynamics of the Fe atoms in the sample, synchrotron Mössbauer spectroscopy (Jackson et al. 2013). A laser heated diamond anvil cell is used to provide the high pressure-high temperature environmental conditions, and in-situ X-ray diffraction is used to constrain the pressure of the sample. To eliminate the influence of temperature fluctuations experienced by the sample on the determination of melting, we develop a Fast Temperature Readout (FasTeR) spectrometer. The FasTeR spectrometer features a fast reading rate (>100 Hz), a high sensitivity, a large dynamic range and a well-constrained focus. By combining the melting curve of fcc-structured Fe0.9Ni0.1 alloy determined in our study and the fcc-hcp phase boundary from Komabayashi et al. (2012), we calculate the fcc-hcp-liquid triple point of Fe0.9Ni0.1. Using this triple point and the thermophysical parameters from a nuclear resonant inelastic X-ray scattering study on hcp-Fe (Murphy et al. 2011), we compute the melting curve of hcp-structured Fe0.9Ni0.1. We will discuss our new experimental results with implications for the cores of Venus, Earth and Mars. Select references: McDonough & Sun (1995): The composition of the Earth. Chem. Geol. 120, 223-253. Jackson et al. (2013): Melting of compressed iron by monitoring atomic dynamics, EPSL, 362, 143-150. Komabayashi et al. (2012): In situ X-ray diffraction measurements of the fcc-hcp phase transition boundary of an Fe-Ni alloy in an internally heated diamond anvil cell, PCM, 39, 329-338. Murphy et al

Cyclic voltammetric study of Co-Ni-Fe alloys electrodeposition in sulfate medium

NASA Astrophysics Data System (ADS)

Hanafi, I.; Daud, A. R.; Radiman, S.

2013-11-01

Electrochemical technique has been used to study the electrodeposition of cobalt, nickel, iron and Co-Ni-Fe alloy on indium tin oxide (ITO) coated glass substrate. To obtain the nucleation mechanism, cyclic voltammetry is used to characterize the Co-Ni-Fe system. The scanning rate effect on the deposition process was investigated. Deposition of single metal occurs at potential values more positive than that estimated stability potential. Based on the cyclic voltammetry results, the electrodeposition of cobalt, nickel, iron and Co-Ni-Fe alloy clearly show that the process of diffusion occurs is controlled by the typical nucleation mechanism.

Effects of Fe concentration on the ion-irradiation induced defect evolution and hardening in Ni-Fe solid solution alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Ke; Guo, Wei; Lu, Chenyang

Understanding alloying effects on the irradiation response of structural materials is pivotal in nuclear engineering. In order to systematically explore the effects of Fe concentration on the irradiation-induced defect evolution and hardening in face-centered cubic Ni-Fe binary solid solution alloys, single crystalline Ni-xFe (x = 0–60 at%) alloys have been grown and irradiated with 1.5 MeV Ni ions. The irradiations have been performed over a wide range of fluences from 3 × 10 13 to 3 × 10 16 cm -2 at room temperature. Ion channeling technique has shown reduced damage accumulation with increasing Fe concentration in the low fluencemore » regime, which is consistent to the results from molecular dynamic simulations. We did not observe any irradiation-induced compositional segregation in atom probe tomography within the detection limit, even in the samples irradiated with high fluence Ni ions. Transmission electron microscopy analyses have further demonstrated that the defect size significantly decreases with increasing Fe concentration, indicating a delay in defect evolution. Furthermore, irradiation induced hardening has been measured by nanoindentation tests. Ni and the Ni-Fe alloys have largely different initial hardness, but they all follow a similar trend for the increase of hardness as a function of irradiation fluence.« less

Effects of Fe concentration on the ion-irradiation induced defect evolution and hardening in Ni-Fe solid solution alloys

DOE PAGES

Jin, Ke; Guo, Wei; Lu, Chenyang; ...

2016-12-01

Understanding alloying effects on the irradiation response of structural materials is pivotal in nuclear engineering. In order to systematically explore the effects of Fe concentration on the irradiation-induced defect evolution and hardening in face-centered cubic Ni-Fe binary solid solution alloys, single crystalline Ni-xFe (x = 0–60 at%) alloys have been grown and irradiated with 1.5 MeV Ni ions. The irradiations have been performed over a wide range of fluences from 3 × 10 13 to 3 × 10 16 cm -2 at room temperature. Ion channeling technique has shown reduced damage accumulation with increasing Fe concentration in the low fluencemore » regime, which is consistent to the results from molecular dynamic simulations. We did not observe any irradiation-induced compositional segregation in atom probe tomography within the detection limit, even in the samples irradiated with high fluence Ni ions. Transmission electron microscopy analyses have further demonstrated that the defect size significantly decreases with increasing Fe concentration, indicating a delay in defect evolution. Furthermore, irradiation induced hardening has been measured by nanoindentation tests. Ni and the Ni-Fe alloys have largely different initial hardness, but they all follow a similar trend for the increase of hardness as a function of irradiation fluence.« less

Chromium Grain-boundary Segregation and Effect of Ion Beam Cleaning on Fe-Ni-Cr Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saraf, Laxmikant V.

2011-04-01

The grain boundaries play important role to control the mechanical strength of ternary alloys. From spacecrafts to naval vessels to nuclear reactors, stress corrosion cracking, brittleness, oxidation mostly originates at the grain boundaries and cause long term structural stability problems in most of the metallic structures [1]. Fe-Ni-Cr based ternary metal alloys have been widely studied for more than fifty years [2, 3]. Despite of vast amount of research, chromium diffusion in stainless steel or other Ni-Fe-Cr based ternary alloys is still an open scientific problem with challenges in structural stability and corrosion resistance [4]. Particularly, austenite Fe-Ni-Cr is lookedmore » upon favorably in space and jet engine industry for their improved resistance to stress corrosion cracking [5]. In solid oxide fuel cells (SOFC), Ni-alloys are frequently used as interconnects and seals [6]. In this communication, simultaneous energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) mapping is utilized to study chemical and structural aspects of chromium segregation in Fe-Ni-Cr alloy. A focused Ga-ion beam is also utilized to study the effect of ion beam cleaning on EBSD image quality (IQ) and inverse pole figure (IPF) maps of Fe-Ni-Cr alloy.« less

Containerless electromagnetic levitation melting of Cu-Fe and Ag-Ni alloys

NASA Technical Reports Server (NTRS)

Abbaschian, G. J.; Ethridge, E. C.

1983-01-01

The feasibility of producing silver or copper alloys containing finely dispersed nickel or iron particles, respectively, by utilizing containerless electromagnetic levitation casting techniques was investigated. A levitation coil was designed to successfully levitate and melt a variety of alloys including Nb-Ge, Cu-Fe, Fe-C, and Ag-Ni. Samples of 70 Cu-30 Fe and 80 Ag-20 Ni (atomic %), prepared by mechanical pressing of the constituent powders, were levitated and heated either to the solid plus liquid range of the alloys or to the fully liquid region. The samples were then solidified by passing helium gas into the bell jar or they were dropped into a quenching oil. The structure of the samples which were heated to the solid plus liquid range consists of uniform distribution of Fe or Ni particle in their respective matrices. A considerable amount of entrapped gas bubbles were contained. Upon heating for longer periods or to higher temperatures, the bubbles coalesced and burst, causing the samples to become fragmented and usually fall out of the coil.

Nucleation of intragranular ferrite in Fe-Ni-P alloys

NASA Astrophysics Data System (ADS)

Narayan, C.; Goldstein, J. I.

1984-05-01

The nucleation of intragranular ferrite from austenite in Fe-Ni-P alloys was investigated in order to understand the development of the Widmanstätten pattern in iron meteorites. Alloys containing 5 to 10 wt pct Ni and 0 to 1 wt pct P were used to simulate iron meteorite compositions. In the isothermal and controlled cooling experiments the reaction path γ → α + γ serves only to nucleate ferrite along austenite grain boundaries. It is necessary for (FeNi)3P to be present within y grains in order to nucleate intragranular ferrite. The reaction path γ → γ + phosphide → α + γ + phosphide yields rod shaped ferrite nuclei that bear a near Kurdjumov-Sachs orientation relationship with the surrounding matrix. The precipitation of ferrite, both along grain boundaries and within the austenite grains, is suppressed in the absence of P.

Plasma-Sprayed High Entropy Alloys: Microstructure and Properties of AlCoCrFeNi and MnCoCrFeNi

NASA Astrophysics Data System (ADS)

Ang, Andrew Siao Ming; Berndt, Christopher C.; Sesso, Mitchell L.; Anupam, Ameey; S, Praveen; Kottada, Ravi Sankar; Murty, B. S.

2015-02-01

High entropy alloys (HEAs) represent a new class of materials that present novel phase structures and properties. Apart from bulk material consolidation methods such as casting and sintering, HEAs can also be deposited as a surface coating. In this work, thermal sprayed HEA coatings are investigated that may be used as an alternative bond coat material for a thermal barrier coating system. Nanostructured HEAs that were based on AlCoCrFeNi and MnCoCrFeNi were prepared by ball milling and then plasma sprayed. Splat studies were assessed to optimise the appropriate thermal spray parameters and spray deposits were prepared. After mechanical alloying, aluminum-based and manganese-based HEA powders revealed contrary prominences of BCC and FCC phases in their X-ray diffraction patterns. However, FCC phase was observed as the major phase present in both of the plasma-sprayed AlCoCrFeNi and MnCoCrFeNi coatings. There were also minor oxide peaks detected, which can be attributed to the high temperature processing. The measured porosity levels for AlCoCrFeNi and MnCoCrFeNi coatings were 9.5 ± 2.3 and 7.4 ± 1.3 pct, respectively. Three distinct phase contrasts, dark gray, light gray and white, were observed in the SEM images, with the white regions corresponding to retained multicomponent HEAs. The Vickers hardness (HV0.3kgf) was 4.13 ± 0.43 and 4.42 ± 0.60 GPa for AlCoCrFeNi and MnCoCrFeNi, respectively. Both type of HEAs coatings exhibited anisotropic mechanical behavior due to their lamellar, composite-type microstructure.

Heat treatment of NiCrFe alloy to optimize resistance to intergrannular stress corrosion

DOEpatents

Steeves, Arthur F.; Bibb, Albert E.

1984-01-01

A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprising heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cool the alloy body, and heat the cooled body to a temperature between 1100.degree. to 1500.degree. F. for about 1 to 30 hours.

Viscosities of Fe Ni, Fe Co and Ni Co binary melts

NASA Astrophysics Data System (ADS)

Sato, Yuzuru; Sugisawa, Koji; Aoki, Daisuke; Yamamura, Tsutomu

2005-02-01

Viscosities of three binary molten alloys consisting of the iron group elements, Fe, Ni and Co, have been measured by using an oscillating cup viscometer over the entire composition range from liquidus temperatures up to 1600 °C with high precision and excellent reproducibility. The viscosities measured showed good Arrhenius linearity for all the compositions. The viscosities of Fe, Ni and Co as a function of temperature are as follows: \\eqalign{ & \\log \\eta={-}0.6074 + 2493/T\\qquad for\\quad Fe\\\\ & \\log \\eta={-}0.5695 + 2157/T\\qquad for\\quad Ni \\\\ & \\log \\eta={-}0.6620 + 2430/T\\qquad for\\quad Co.} The isothermal viscosities of Fe-Ni and Fe-Co binary melts increase monotonically with increasing Fe content. On the other hand, in Ni-Co binary melt, the isothermal viscosity decreases slightly and then increases with increasing Co. The activation energy of Fe-Co binary melt increased slightly on mixing, and those of Fe-Ni and Ni-Co melts decreased monotonically with increasing Ni content. The above behaviour is discussed based on the thermodynamic properties of the alloys.

Forming a structure of the CoNiFe alloys by X-ray irradiation

NASA Astrophysics Data System (ADS)

Valko, Natalia; Kasperovich, Andrey; Koltunowicz, Tomasz N.

The experimental data of electrodeposition kinetics researches and structure formation of ternary CoNiFe alloys deposited onto low-carbon steel 08kp in the presence of X-rays are presented. Relations of deposit rate, current efficiencies, element and phase compositions of CoNiFe coatings formed from sulfate baths with respect to cathode current densities (0.5-3A/dm2), electrolyte composition and irradiation were obtained. It is shown that, the CoNiFe coatings deposited by the electrochemical method involving exposure of the X-rays are characterized by more perfect morphology surfaces with less developed surface geometry than reference coatings. The effect of the X-ray irradiation on the electrodeposition of CoNiFe coatings promotes formatting of alloys with increased electropositive component and modified phase composition.

Effects of environment on the release of Ni, Cr, Fe, and Co from new and recast Ni-Cr alloy.

PubMed

Oyar, Perihan; Can, Gülşen; Atakol, Orhan

2014-07-01

The addition of previously cast alloy to new alloy for economic reasons may increase the release of elements. The purpose of this study was to analyze the effects of the immersion period, immersion media, and addition of previously cast alloy to new alloy on the release of elements. Disk-shaped specimens were prepared from a Ni-Cr alloy (Ni: 61 wt%, Cr: 26 wt%, Mo: 11 wt%, Si: 1.5 wt%, Fe, Ce, Al, and Co <1 wt%) (Remanium CS; Dentaurum) with new alloy (group N) and 50% new/50% recast alloy (group R). After the immersion of the specimens in both NaCl (pH 4) and artificial saliva (pH 6.7) for 3, 7, 14, 30, and 60 days, the release of ions was determined by using atomic absorption spectrometry. Data were analyzed with a 3-way ANOVA (α=.001). The release of Ni was significantly affected by the immersion period, of Ni and Cr by the alloy and media (P<.01), and of Fe by the alloy (P<.01). Ion release from the recast alloy in artificial saliva was 109.71 for Ni, 6.49 for Cr, 223.22 for Fe, and 29.90 μg/L for Co. The release of Co in NaCl was below the detection limit in both groups. The release of Ni in NaCl and artificial saliva increased with the length of the immersion period in both groups. The release of Cr and Fe was higher in artificial saliva than in NaCl in group R, regardless of the immersion period. The release of Co in NaCl was below the detection limit in both groups. Copyright © 2014 The Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Preferential diffusion in concentrated solid solution alloys: NiFe, NiCo and NiCoCr

DOE PAGES

Zhao, Shijun; Osetsky, Yuri; Zhang, Yanwen

2017-02-13

In single-phase concentrated solid-solution alloys (CSAs), including high entropy alloys (HEAs), remarkable mechanical properties are exhibited, as well as extraordinary corrosion and radiation resistance compared to pure metals and dilute alloys. But, the mechanisms responsible for these properties are unknown in many cases. In this work, we employ ab initio molecular dynamics based on density functional theory to study the diffusion of interstitial atoms in Ni and Ni-based face-centered cubic CSAs including NiFe, NiCo and NiCoCr. We model the defect trajectories over >100 ps and estimate tracer diffusion coefficients, correlation factors and activation energies. Furthermore, we found that the diffusionmore » mass transport in CSAs is not only slower than that in pure components, i.e. sluggish diffusion, but also chemically non-homogeneous. The results obtained here can be used in understanding and predicting the atomic segregation and phase separation in CSAs under irradiation conditions.« less

Mechanisms of radiation-induced segregation in CrFeCoNi-based single-phase concentrated solid solution alloys

DOE PAGES

He, Mo-Rigen; Wang, Shuai; Shi, Shi; ...

2016-12-31

Single-phase concentrated solid solution alloys have attracted wide interest due to their superior mechanical properties and enhanced radiation tolerance, which make them promising candidates for the structural applications in next-generation nuclear reactors. However, little has been understood about the intrinsic stability of their as-synthesized, high-entropy configurations against radiation damage. In this paper, we report the element segregation in CrFeCoNi, CrFeCoNiMn, and CrFeCoNiPd equiatomic alloys when subjected to 1250 kV electron irradiations at 400 °C up to a damage level of 1 displacement per atom. Cr/Fe/Mn/Pd can deplete and Co/Ni can accumulate at radiation-induced dislocation loops, while the actively segregating elementsmore » are alloy-specific. Moreover, electron-irradiated matrix of CrFeCoNiMn and CrFeCoNiPd shows L1 0 (NiMn)-type ordering decomposition and <001>-oriented spinodal decomposition between Co/Ni and Pd, respectively. Finally, these findings are rationalized based on the atomic size difference and enthalpy of mixing between the alloying elements, and identify a new important requirement to the design of radiation-tolerant alloys through modification of the composition.« less

Auger electron diffraction study of Fe 1- xNi x alloys epitaxially grown on Cu(100)

NASA Astrophysics Data System (ADS)

Martin, M. G.; Foy, E.; Chevrier, F.; Krill, G.; Asensio, M. C.

1999-08-01

We have combined Auger electron diffraction (AED), low-energy electron diffraction (LEED) and high-energy electron diffraction (RHEED) to examine the structure of Fe xNi 1- x alloys when the Fe content approaches 65%. At this concentration, the 'invar effect' takes place, so the magnetization falls to zero, and the thermal expansion coefficient is very small. The Fe xNi 1- x alloys, grown as metastable thin films by molecular-beam epitaxy on Cu(100) substrates, were studied as a function of the x stoichiometry. In contrast to the related bulk alloy compounds, we observe the collapse of the fcc-to-bcc structural transition in the Fe-rich films. Furthermore, the local atomic structure around Fe and Ni in the alloy has been simultaneously determined by the angular intensity distributions of Fe L 3VV (703 eV) and Ni L 3VV (848 eV) Auger electrons measured as a function of polar and azimuthal angles. For the films deposited at room temperature, we have confirmed the pseudomorphic growth morphology and the uniformity of the alloys.

Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

DOE PAGES

Zhang, Chuan; Zhang, Fan; Diao, Haoyan; ...

2016-07-19

The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chuan; Zhang, Fan; Diao, Haoyan

The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

Effects of Ni content on nanocrystalline Fe-Co-Ni ternary alloys synthesized by a chemical reduction method

NASA Astrophysics Data System (ADS)

Chokprasombat, Komkrich; Pinitsoontorn, Supree; Maensiri, Santi

2016-05-01

Magnetic properties of Fe-Co-Ni ternary alloys could be altered by changing of the particle size, elemental compositions, and crystalline structures. In this work, Fe50Co50-xNix nanoparticles (x=10, 20, 40, and 50) were prepared by the novel chemical reduction process. Hydrazine monohydrate was used as a reducing agent under the concentrated basic condition with the presence of poly(vinylpyrrolidone). We found that the nanoparticles were composed of Fe, Co and Ni with compositions according to the molar ratio of the metal sources. Interestingly, the particles were well-crystalline at the as-prepared state without post-annealing at high temperature. Increasing Ni content resulted in phase transformation from body centered cubic (bcc) to face centered cubic (fcc). For the fcc phase, the average particle size decreased when increased the Ni content; the Fe50Ni50 nanoparticles had the smallest average size with the narrowest size distribution. In additions, the particles exhibited ferromagnetic properties at room temperature with the coercivities higher than 300 Oe, and the saturation magnetiation decreased with increasing Ni content. These results suggest that the structural and magnetic properties of Fe-Co-Ni alloys could be adjusted by varying the Ni content.

Elastic moduli and thermal expansion coefficients of medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy

DOE PAGES

Laplanche, Guillaume; Gadaud, P.; Barsch, C.; ...

2018-02-23

Elastic moduli of a set of equiatomic alloys (CrFeCoNi, CrCoNi, CrFeNi, FeCoNi, MnCoNi, MnFeNi, and CoNi), which are medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy were determined as a function of temperature over the range 293 K–1000 K. Thermal expansion coefficients were determined for these alloys over the temperature range 100 K–673 K. All alloys were single-phase and had the face-centered cubic (FCC) crystal structure, except CrFeNi which is a two-phase alloy containing a small amount of body-centered cubic (BCC) precipitates in a FCC matrix. The temperature dependences of thermal expansion coefficients and elastic moduli obtained here are useful formore » quantifying fundamental aspects such as solid solution strengthening, and for structural analysis/design. Furthermore, using the above results, the yield strengths reported in literature for these alloys were normalized by their shear moduli to reveal the influence of shear modulus on solid solution strengthening.« less

Elastic moduli and thermal expansion coefficients of medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laplanche, Guillaume; Gadaud, P.; Barsch, C.

Elastic moduli of a set of equiatomic alloys (CrFeCoNi, CrCoNi, CrFeNi, FeCoNi, MnCoNi, MnFeNi, and CoNi), which are medium-entropy subsystems of the CrMnFeCoNi high-entropy alloy were determined as a function of temperature over the range 293 K–1000 K. Thermal expansion coefficients were determined for these alloys over the temperature range 100 K–673 K. All alloys were single-phase and had the face-centered cubic (FCC) crystal structure, except CrFeNi which is a two-phase alloy containing a small amount of body-centered cubic (BCC) precipitates in a FCC matrix. The temperature dependences of thermal expansion coefficients and elastic moduli obtained here are useful for quantifying fundamental aspects suchmore » as solid solution strengthening, and for structural analysis/design. Furthermore, using the above results, the yield strengths reported in literature for these alloys were normalized by their shear moduli to reveal the influence of shear modulus on solid solution strengthening.« less

Heat treatment of NiCrFe alloy 600 to optimize resistance to intergranular stress corrosion

DOEpatents

Steeves, A.F.; Bibb, A.E.

A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprises heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cooling the alloy body, and heating the cooled body to a temperature between 1100 to 1500/sup 0/F for about 1 to 30 hours.

Static compression of Fe 0.83Ni 0.09Si 0.08 alloy to 374 GPa and Fe 0.93Si 0.07 alloy to 252 GPa: Implications for the Earth's inner core

NASA Astrophysics Data System (ADS)

Asanuma, Hidetoshi; Ohtani, Eiji; Sakai, Takeshi; Terasaki, Hidenori; Kamada, Seiji; Hirao, Naohisa; Ohishi, Yasuo

2011-10-01

The pressure-volume equations of state of iron-nickel-silicon alloy Fe 0.83Ni 0.09Si 0.08 (Fe-9.8 wt.% Ni-4.0 wt.% Si) and iron-silicon alloy Fe 0.93Si 0.07 (Fe-3.4 wt.% Si) have been investigated up to 374 GPa and 252 GPa, respectively. The present compression data covered pressures of the Earth's core. We confirmed that both Fe 0.83Ni 0.09Si 0.08 and Fe 0.93Si 0.07 alloys remain in the hexagonal close packed structure at all pressures studied. We obtained the density of these alloys at the pressure of the inner core boundary (ICB), 330 GPa at 300 K by fitting the compression data to the third order Birch-Murnaghan equation of state. Using these density values combined with the previous data for hcp-Fe, hcp-Fe 0.8Ni 0.2, and hcp-Fe 0.84Si 0.16 alloys and comparing with the density of the PREM inner core, we estimated the Ni and Si contents of the inner core. The Si content of the inner core estimated here is slightly greater than that estimated previously based on the sound velocity measurement of the hcp-Fe-Ni-Si alloy at high pressure.

Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

NASA Astrophysics Data System (ADS)

Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

2016-06-01

In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

Oxidation sulfidation resistance of Fe-Cr-Ni alloys

DOEpatents

Natesan, Ken; Baxter, David J.

1984-01-01

High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1-8 wt. % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500.degree.-1000.degree. C.

Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teng, Zhenke; Zhang, F; Miller, Michael K

2012-01-01

NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model inmore » the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.« less

Role of lead in electrochemical reaction of alloy 600, alloy 690, Ni, Cr, and Fe in water

NASA Astrophysics Data System (ADS)

Hwang, Seong Sik; Kim, Joung Soo; Kim, Ju Yup

2003-08-01

It has been reported that lead causes stress corrosion cracking (SCC) in the secondary side of steam generators (SG) in pressurized water reactors (PWR). The materials of SG tubings are alloy 600, alloy 690, or alloy 800, among which the main alloying elements are Ni, Cr, and Fe. The effect of lead on the electrochemical behaviors of alloy 600 and alloy 690 using an anodic polarization technique was evaluated. We also obtained polarization curves of pure Ni, Cr, and Fe in water containing lead. As the amount of lead in the solution increased, critical current densities and passive current densities of alloy 600 and alloy 690 increased, while the breakdown potential of the alloys decreased. Lead increased critical current density and the passive current of Cr in pH 4 and pH 10. The instability of passive film of steam generator tubings in water containing lead might arise from the instability of Cr passivity.

Siderophile trace element diffusion in Fe-Ni alloys

NASA Astrophysics Data System (ADS)

Watson, Heather C.; Watson, E. Bruce

2003-09-01

Experiments were performed in a piston cylinder apparatus to characterize the diffusion behavior of the siderophile elements, Mo, Cu, Pd, Au, and Re in solid Fe-Ni alloy (90 wt.% Fe, 10 wt.% Ni). All experiments were conducted at 1 GPa and temperatures ranging from 1175 to 1400 °C. Activation energies of all elements fall between 270 kJ/mol (Cu) and 360 kJ/mol (Mo). Mo, Cu, Pd, and Au all show similar diffusivities at the same conditions, but the diffusivity of Re was consistently close to an order of magnitude lower. Initial experiments on other refractory elements (Os, Pt, and Ir) indicate that their diffusivities are close to or slightly lower than that of Re.

Magnetic cluster expansion model for random and ordered magnetic face-centered cubic Fe-Ni-Cr alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavrentiev, M. Yu., E-mail: Mikhail.Lavrentiev@ukaea.uk; Nguyen-Manh, D.; Dudarev, S. L.

A Magnetic Cluster Expansion model for ternary face-centered cubic Fe-Ni-Cr alloys has been developed, using DFT data spanning binary and ternary alloy configurations. Using this Magnetic Cluster Expansion model Hamiltonian, we perform Monte Carlo simulations and explore magnetic structures of alloys over the entire range of compositions, considering both random and ordered alloy structures. In random alloys, the removal of magnetic collinearity constraint reduces the total magnetic moment but does not affect the predicted range of compositions where the alloys adopt low-temperature ferromagnetic configurations. During alloying of ordered fcc Fe-Ni compounds with Cr, chromium atoms tend to replace nickel rathermore » than iron atoms. Replacement of Ni by Cr in ordered alloys with high iron content increases the Curie temperature of the alloys. This can be explained by strong antiferromagnetic Fe-Cr coupling, similar to that found in bcc Fe-Cr solutions, where the Curie temperature increase, predicted by simulations as a function of Cr concentration, is confirmed by experimental observations. In random alloys, both magnetization and the Curie temperature decrease abruptly with increasing chromium content, in agreement with experiment.« less

The Effect of Metal Composition on Fe-Ni Partition Behavior between Olivine and FeNi-Metal, FeNi-Carbide, FeNi-Sulfide at Elevated Pressure

NASA Technical Reports Server (NTRS)

Holzheid, Astrid; Grove, Timothy L.

2005-01-01

Metal-olivine Fe-Ni exchange distribution coefficients were determined at 1500 C over the pressure range of 1 to 9 GPa for solid and liquid alloy compositions. The metal alloy composition was varied with respect to the Fe/Ni ratio and the amount of dissolved carbon and sulfur. The Fe/Ni ratio of the metal phase exercises an important control on the abundance of Ni in the olivine. The Ni abundance in the olivine decreases as the Fe/Ni ratio of the coexisting metal increases. The presence of carbon (up to approx. 3.5 wt.%) and sulfur (up to approx. 7.5 wt.%) in solution in the liquid Fe-Ni-metal phase has a minor effect on the partitioning of Fe and Ni between metal and olivine phases. No pressure dependence of the Fe-Ni-metal-olivine exchange behavior in carbon- and sulfur-free and carbon- and sulfur-containing systems was found within the investigated pressure range. To match the Ni abundance in terrestrial mantle olivine, assuming an equilibrium metal-olivine distribution, a sub-chondritic Fe/Ni-metal ratio that is a factor of 17 to 27 lower than the Fe/Ni ratios in estimated Earth core compositions would be required, implying higher Fe concentrations in the core forming metal phase. A simple metal-olivine equilibrium distribution does not seem to be feasible to explain the Ni abundances in the Earth's mantle. An equilibrium between metal and olivine does not exercise a control on the problem of Ni overabundance in the Earth's mantle. The experimental results do not contradict the presence of a magma ocean at the time of terrestrial core formation, if olivine was present in only minor amounts at the time of metal segregation.

Simultaneous enhancement of magnetic and mechanical properties in Ni-Mn-Sn alloy by Fe doping

PubMed Central

Tan, Changlong; Tai, Zhipeng; Zhang, Kun; Tian, Xiaohua; Cai, Wei

2017-01-01

Both magnetic-field-induced reverse martensitic transformation (MFIRMT) and mechanical properties are crucial for application of Ni-Mn-Sn magnetic shape memory alloys. Here, we demonstrate that substitution of Fe for Ni can simultaneously enhance the MFIRMT and mechanical properties of Ni-Mn-Sn, which are advantageous for its applications. The austenite in Ni44Fe6Mn39Sn11 shows the typical ferromagnetic magnetization with the highest saturation magnetization of 69 emu/g at 223 K. The result shows that an appropriate amount of Fe substitution can really enhance the ferromagnetism of Ni50Mn39Sn11 alloy in austenite, which directly leads to the enhancement of MFIRMT. Meanwhile, the mechanical property significantly improves with Fe doping. When there is 4 at.% Fe added, the compressive and maximum strain reach the maximum value (approximately 725.4 MPa and 9.3%). Furthermore, using first-principles calculations, we clarify the origin of Fe doping on martensitic transformation and magnetic properties. PMID:28230152

Fe-based long range ordered alloys

DOEpatents

Liu, Chain T; Inouye, Henry; Schaffhauser, Anthony C.

1980-01-01

Malleable long range ordered alloys having high critical ordering temperatures exist in the V(Co,Fe).sub.3 and V(Co,Fe,Ni).sub.3 system having the composition comprising by weight 22-23% V, 35-50% Fe, 0-22% Co and 19-40% Ni with an electron density no greater than 8.00. Excellent high temperature properties occur in alloys having compositions comprising by weight 22-23% V, 35-45% Fe, 0-10% Co, 25-35% Ni; 22-23% V, 28-33% Ni and the remainder Fe; and 22-23% V, 19-22% Ni, 19-22% Co and the remainder Fe. The alloys are fabricable by casting, deforming and annealing for sufficient time to provide ordered structure.

The Effect of Composition on Diffusion of Au in Fe and Fe-Ni Alloys

NASA Astrophysics Data System (ADS)

Johanesen, K. E.; Watson, H. C.; Fei, Y.

2005-12-01

Understanding siderophile element diffusion in Fe-Ni alloys will lead to tighter constraints on processes such as meteoritic body cooling rates, and inner core-outer core communication. Recent studies have determined the effect of temperature and pressure on diffusion in this system, but the effect of composition has not yet been explored adequately. The effect of Ni content on Au diffusion in an Fe-Ni system was explored for Fe-Ni alloys with concentrations of 0, 20, and 30 wt. % Ni. Diffusion couple experiments were conducted using a piston cylinder press at 1 GPa and temperatures ranging from 1150°C to 1400°C. Concentration profiles were measured by electron microprobe and were fitted to the linear diffusion solution for an semi-infinite diffusion couple to extract diffusion coefficients (D) using a non-linear least squares fit routine. As predicted, D increases with Ni content and also with temperature. The diffusivities ranged from 2.06×10-9 at 1150°C to 5.76×10-8 at 1350°C for 0 wt. % Ni; 5.17×10-9 at 1150° C to 1.93×10-7 at 1400°C for 20 wt. % Ni; and 2.41×10-8 at 1150°C to 2.13×10-7 at 1400°C for 30 wt. % Ni. As temperature increases, the effect of Ni on diffusion rates increases, implying a possible change in diffusion mechanism between 1250°C and 1300°C. Ni appears to have a negligible effect at lower temperatures, which would indicate that Ni may not need to be considered when modeling siderophile trace element diffusion rates in iron meteorites.

Physical and Mechanical Properties of LoVAR: A New Lightweight Particle-Reinforced Fe-36Ni Alloy

NASA Technical Reports Server (NTRS)

Stephenson, Timothy; Tricker, David; Tarrant, Andrew; Michel, Robert; Clune, Jason

2015-01-01

Fe-36Ni is an alloy of choice for low thermal expansion coefficient (CTE) for optical, instrument and electrical applications in particular where dimensional stability is critical. This paper outlines the development of a particle-reinforced Fe-36Ni alloy that offers reduced density and lower CTE compared to the matrix alloy. A summary of processing capability will be given relating the composition and microstructure to mechanical and physical properties.

Low-cost Fe--Ni--Cr alloys for high temperature valve applications

DOEpatents

Muralidharan, Govindarajan

2017-03-28

An Fe--Ni--Cr alloy is composed essentially of, in terms of weight percent: 1 to 3.5 Al, up to 2 Co, 15 to 19.5 Cr, up to 2 Cu, 23 to 40 Fe, up to 0.3 Hf, up to 4 Mn, 0.15 to 2 Mo, up to 0.15 Si, up to 1.05 Ta, 2.8 to 4.3 Ti, up to 0.5 W, up to 0.06 Zr, 0.02 to 0.15 C, 0.0001 to 0.007 N, balance Ni, wherein, in terms of atomic percent: 6.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.10, 0.33.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.065, 4.ltoreq.(Fe+Cr)/(Al+Ti+Zr+Hf+Ta).ltoreq.10, the alloy being essentially free of Nb and V.

Chemical synthesis of L10 Fe-Pt-Ni alloy nanoparticles

NASA Astrophysics Data System (ADS)

Deepchand, Vimal; Abel, Frank M.; Tzitzios, Vasileios; Hadjipanayis, George C.

2018-05-01

This work focuses on the study of the magnetic and structural properties of chemically synthesized FePt1-xNix nanoparticles, with Ni content x in the range 0.2-0.4. We report the effect of Ni substitution on the L10 structure, on both the as-synthesized and annealed nanoparticles. A decrease in nanoparticle size as well as in chemical order is observed with an increase in Ni content, for both the as-made and annealed nanoparticles. The results also show that the post annealing procedure at 700oC significantly enhanced the L10 ordering of the nanoparticles. Substitution of nickel leads to a decrease in coercivity from 14.9 kOe in FePt to 0.8 kOe for FePt0.6Ni0.4 alloy, while the magnetization at 3 T is increased from 48 emu/g to 88 emu/g.

Improved oxidation sulfidation resistance of Fe-Cr-Ni alloys

DOEpatents

Natesan, K.; Baxter, D.J.

1983-07-26

High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1 to 8 wt % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500 to 1000/sup 0/C.

The effect of Mn/Ni on thermodynamic properties of critical nucleus in Fe-Cu-Mn (Ni) ternary alloys

DOE PAGES

Li, Boyan; Zhang, Lei; Li, Chengliang; ...

2018-04-18

The aging- or radiation-induced hardening of Cu/Mn/Ni precipitates in Fe alloys is one of property degradation mechanisms in structural materials in nuclear reactors. Experiments show that aging or radiation leads the formation of Cu-rich precipitates, and the addition of Mn or Ni elements enhances the precipitation kinetics. In this study, the phase-field model coupled with the constrained string method have been applied to investigate the thermodynamic properties of critical nuclei such as the minimum energy path of Cu/Mn/Ni precipitation in Fe-Cu-Mn and Fe-Cu-Ni ternary alloys. The chemical free energies used in the model are taken from CALPHAD. The simulation resultsmore » show that the formation of Cu/Mn/Ni clusters needs to overcome an energy barrier, and the precipitate has a Core-Shell structure. The thermodynamic properties of the critical nucleus are influenced by temperature and Cu/Mn/Ni overall concentrations, which are in accordance with the simulation results as well as the experimental observations.« less

The effect of Mn/Ni on thermodynamic properties of critical nucleus in Fe-Cu-Mn (Ni) ternary alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Boyan; Zhang, Lei; Li, Chengliang

The aging- or radiation-induced hardening of Cu/Mn/Ni precipitates in Fe alloys is one of property degradation mechanisms in structural materials in nuclear reactors. Experiments show that aging or radiation leads the formation of Cu-rich precipitates, and the addition of Mn or Ni elements enhances the precipitation kinetics. In this study, the phase-field model coupled with the constrained string method have been applied to investigate the thermodynamic properties of critical nuclei such as the minimum energy path of Cu/Mn/Ni precipitation in Fe-Cu-Mn and Fe-Cu-Ni ternary alloys. The chemical free energies used in the model are taken from CALPHAD. The simulation resultsmore » show that the formation of Cu/Mn/Ni clusters needs to overcome an energy barrier, and the precipitate has a Core-Shell structure. The thermodynamic properties of the critical nucleus are influenced by temperature and Cu/Mn/Ni overall concentrations, which are in accordance with the simulation results as well as the experimental observations.« less

Room-temperature ferromagnetic transitions and the temperature dependence of magnetic behaviors in FeCoNiCr-based high-entropy alloys

NASA Astrophysics Data System (ADS)

Na, Suok-Min; Yoo, Jin-Hyeong; Lambert, Paul K.; Jones, Nicholas J.

2018-05-01

High-entropy alloys (HEAs) containing multiple principle alloying elements exhibit unique properties so they are currently receiving great attention for developing innovative alloy designs. In FeCoNi-based HEAs, magnetic behaviors strongly depend on the addition of alloying elements, usually accompanied by structural changes. In this work, the effect of non-magnetic components on the ferromagnetic transition and magnetic behaviors in equiatomic FeCoNiCrX (X=Al, Ga, Mn and Sn) HEAs was investigated. Alloy ingots of nominal compositions of HEAs were prepared by arc melting and the button ingots were cut into discs for magnetic measurements as functions of magnetic field and temperature. The HEAs of FeCoNiCrMn and FeCoNiCrSn show typical paramagnetic behaviors, composed of solid solution FCC matrix, while the additions of Ga and Al in FeCoNiCr exhibit ferromagnetic behaviors, along with the coexistence of FCC and BCC phases due to spinodal decomposition. The partial phase transition in both HEAs with the additions of Ga and Al would enhance ferromagnetic properties due to the addition of the BCC phase. The saturation magnetization for the base alloy FeCoNiCr is 0.5 emu/g at the applied field of 20 kOe (TC = 104 K). For the HEAs of FeCoNiCrGa and FeCoNiCrAl, the saturation magnetization significantly increased to 38 emu/g (TC = 703 K) and 25 emu/g (TC = 277 K), respectively. To evaluate the possibility of solid solution FCC and BCC phases in FeCoNiCr-type HEAs, we introduced a parameter of valence electron concentration (VEC). The proposed rule for solid solution formation by the VEC was matched with FeCoNiCr-type HEAs.

Phase relations of Fe Ni alloys at high pressure and temperature

NASA Astrophysics Data System (ADS)

Mao, Wendy L.; Campbell, Andrew J.; Heinz, Dion L.; Shen, Guoyin

2006-04-01

Using a diamond anvil cell and double-sided laser-heating coupled with synchrotron X-ray diffraction, we determined phase relations for three compositions of Fe-rich FeNi alloys in situ at high pressure and high temperature. We studied Fe with 5, 15, and 20 wt.% Ni to 55, 62, and 72 GPa, respectively, at temperatures up to ˜3000 K. Ni stabilizes the face-centered cubic phase to lower temperatures and higher pressure, and this effect increases with increasing pressure. Extrapolation of our experimental results for Fe with 15 wt.% Ni suggests that the stable phase at inner core conditions is hexagonal close packed, although if the temperature at the inner core boundary is higher than ˜6400 K, a two phase outer region may also exist. Comparison to previous laser-heated diamond anvil cell studies demonstrates the importance of kinetics even at high temperatures.

First-Principles Study on the Gilbert Damping Constants of Transition Metal Alloys, Fe--Ni and Fe--Pt Systems

NASA Astrophysics Data System (ADS)

Sakuma, Akimasa

2012-08-01

We adapt the tight-binding linear muffin-tin orbital (TB-LMTO) method to the torque-correlation model for the Gilbert damping constant α and perform the first-principles calculation for disordered transition metal alloys, Fe--Ni and Fe--Pt systems, within the framework of the CPA. Quantitatively, the calculated α values are about one-half of the experimental values, whereas the variations in the Fermi level dependence of α are much larger than these discrepancies. As expected, we confirm in the (Fe--Ni)1-XPtX and FePt systems that Pt atoms certainly enhance α owing to their large spin--orbit coupling. For the disordered alloys, we find that α decreases with increasing chemical degree of order in a wide range.

Phase stability and magnetic behavior of FeCrCoNiGe high-entropy alloy

NASA Astrophysics Data System (ADS)

Huang, Shuo; Vida, Ádám; Molnár, Dávid; Kádas, Krisztina; Varga, Lajos Károly; Holmström, Erik; Vitos, Levente

2015-12-01

We report an alternative FeCrCoNiGe magnetic material based on FeCrCoNi high-entropy alloy with Curie point far below the room temperature. Investigations are done using first-principles calculations and key experimental measurements. Results show that the equimolar FeCrCoNiGe system is decomposed into a mixture of face-centered cubic and body-centered cubic solid solution phases. The increased stability of the ferromagnetic order in the as-cast FeCrCoNiGe composite, with measured Curie temperature of 640 K, is explained using the exchange interactions.

Fe-based long range ordered alloys

DOEpatents

Liu, C.T.

Malleable long range ordered alloys with high critical ordering temperatures exist in the V(Co,Fe)/sub 3/ and V(Co,Fe,Ni)/sub 3/ system. The composition comprising by weight 22 to 23% V, 35 to 50% Fe, 0 to 22% Co and 19 to 40% Ni with an electron density no greater than 8.00. Excellent high temperature properties occur in alloys having compositions comprising by weight 22 to 23% V, 35 to 45% Fe, 0 to 10% Co, 25 to 35% Ni; 22 to 23% V, 28 to 33% Ni and the remainder Fe; and 22 to 23% V, 19 to 22% Co and the remainder Fe. The alloys are fabricable by casting, deforming and annealing for sufficient time to provide ordered structure.

Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 under Sodium Chloride Aqueous Conditions

DOE PAGES

Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.; ...

2018-01-01

The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less

Effect of Molybdenum on the Corrosion Behavior of High-Entropy Alloys CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 under Sodium Chloride Aqueous Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, Alvaro A.; Tylczak, Joseph H.; Gao, Michael C.

The corrosion behavior of high-entropy alloys (HEAs) CoCrFeNi 2 and CoCrFeNi 2 Mo 0.25 was investigated in 3.5 wt. percent sodium chloride (NaCl) at 25°C by electrochemical methods. Their corrosion parameters were compared to those of HASTELLOY® C-276 (UNS N10276) and stainless steel 316L (UNS 31600) to assess the suitability of HEAs for potential industrial applications in NaCl simulating seawater type environments. The corrosion rates were calculated using corrosion current determined from electrochemical experiments for each of the alloys. In addition, potentiodynamic polarization measurements can indicate active, passive, and transpassive behavior of the metal as well as potential susceptibility to pittingmore » corrosion. Cyclic voltammetry (CV) can confirm the alloy susceptibility to pitting corrosion. Electrochemical impedance spectroscopy (EIS) elucidates the corrosion mechanism under studied conditions. The results of the electrochemical experiments and scanning electron microscopy (SEM) analyses of the corroded surfaces revealed general corrosion on alloy CoCrFeNi 2 Mo 0.25 and HASTELLOY C-276 and pitting corrosion on alloy CoCrFeNi 2 and stainless steel 316L.« less

Magnetic Mineralogy of Troilite-Inclusions and their Fe-Ni Host Alloys in IAB Iron Meteorites

NASA Astrophysics Data System (ADS)

Kontny, A. M.; Kramar, U.; Luecke, W.

2011-12-01

Iron-nickel meteorites often contain isolated, mostly rounded troilite nodules enclosed in a bulk of Fe-Ni alloy. As sulfur has a low solubility in metal, it is excluded from the crystallization of metal during cooling. Therefore troilite nodules are interpreted to be trapped droplets of residual sulfur-enriched melts. Microscopic examinations of the interface (mm-range) between troilite inclusions and Fe-Ni alloy yield clear mineralogical differences compared to the troilite inclusion. Such rims around troilite nodules seem to occur exclusively in Fe-Ni meteorites with slow cooling rates, and therefore might provide interesting clues on segregation, fractional crystallization and reequilibration processes between the Fe-Ni alloy and the sulfide phases. These interfaces however are also highly sensitive to terrestrial weathering. We present microscopic observations in combination with temperature-dependent magnetic susceptibility (k-T curves) in order to identify the magnetic mineralogy of the Morasko (Poland) and Coahuila (Mexico) meteorites, which both geochemically belong to the non-magmatic IAB or IIICD group. In the k-T curves both, rim and troilite nodule are characterized by Curie temperatures (TC) that can be related to magnetite, daubreelite (FeCr2O4), Fe-hydroxide and sometimes cohenite. Therefore the interface seems to be geochemically more similar to the troilite nodule than the Fe-Ni alloy. Optical microscopy in combination with the ferrofluid method revealed complex microstructures of intergrown magnetic (TC = 780-785 °C) and non-magnetic phases in the Fe-Ni alloy, which differ in their Ni-concentration. Towards the rim of the troilite nodule the concentration of magnetic cohenite ((Fe,Ni)3C) and especially schreibersite ((Fe,Ni)3P), which are both intergrown with the metal, increases. Cohenite is easily identified microscopically by a very characteristic stripe-like magnetic domain structure and it shows a TC at about 200 °C. The carbon-rich, dark

Effects of the addition of Co, Ni or Cr on the decolorization properties of Fe-Si-B amorphous alloys

NASA Astrophysics Data System (ADS)

Zhang, Changqin; Zhu, Zhengwang; Zhang, Haifeng

2017-11-01

Fe-based amorphous alloys show great potential in degrading azo dyes and other organic pollutants, and are widely investigated as a kind of environmental-friendly materials for wastewater remediation. In this paper, the effects of Co, Ni or Cr addition on the decolorization properties of Fe-Si-B amorphous alloys were studied, and the mechanism of their different effects was analyzed. Co addition could lower the activation energy of Fe-Si-B amorphous alloys in decolorizing azo dyes, and had no weakening effect on the decolorization capability of Fe-Si-B amorphous alloys. Ni addition led to partial crystallization of Fe-Si-B amorphous alloys, and the decolorization mechanism at low temperatures changed from chemical degradation to physical adsorption. Cr addition could enhance the corrosion resistance of Fe-Si-B amorphous alloys, but the amorphous alloys completely lost the decolorization capability no matter at lower or higher temperatures. The results of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) indicated that the addition of Co, Ni or Cr could generate different surface structures that had significant influences on the decolorization process. Our work demonstrated that the effiecient decolorization of azo dyes by Fe-based alloys could be realized only when amorphous nature and incompact surface structure were simultaneously achieved for the alloys.

Equations of state and anisotropy of Fe-Ni-Si alloys

NASA Astrophysics Data System (ADS)

Morrison, R. A.; Jackson, J. M.; Sturhahn, W.; Zhang, D.; Greenberg, E.

2017-12-01

Seismic observations provide constraints on the density, bulk sound speed, and bulk modulus of Earth's inner core, and x-ray diffraction (XRD) experiments can experimentally constrain such properties of iron alloys. The deviation of these seismically-inferred values from the properties of iron suggests the presence of light elements (e.g. Si, O, S, C, H) inside the core. While cosmochemical studies suggest Earth's core is composed primarily of iron alloyed with 5 wt% nickel, existing experimental XRD studies constraining pressure-density relations have predominantly focused on iron and iron alloyed with light elements, while neglecting the effect of nickel. In this study, we present high-precision equations of state for bcc- and hcp-structured Fe0.91Ni0.09 and Fe0.80Ni0.10Si0.10 using powder XRD at room temperature up to 167 GPa and 175 GPa, respectively. By using tungsten powder as a pressure calibrant and helium as a pressure transmitting medium, we minimize error due to pressure calibration and non-hydrostatic stresses. The results are high fidelity equations of state (EOS). By systematically comparing our findings to an established EOS of hcp-Fe [Dewaele et al. 2006], we constrain the effect of nickel and silicon on the density, bulk sound speed, and bulk modulus of iron alloys, which is a critical step towards constraining the inner core's composition. We find that for iron alloys, high quality ambient temperature EOSs can dramatically improve the extrapolated high temperature equations of state to inner core conditions. By combining seismic observations and their associated uncertainties with our data and existing Fe light-element-alloy EOSs, we estimate their densities, bulk moduli, and bulk sound speeds at inner core conditions and propose an experimentally and seismologically consistent range of inner core compositions. Additionally, we obtain an unprecedented constraint on the effect of nickel and silicon on the axial ratio of iron alloys. Nickel has a

High-temperature oxidation of advanced FeCrNi alloy in steam environments

NASA Astrophysics Data System (ADS)

Elbakhshwan, Mohamed S.; Gill, Simerjeet K.; Rumaiz, Abdul K.; Bai, Jianming; Ghose, Sanjit; Rebak, Raul B.; Ecker, Lynne E.

2017-12-01

Alloys of iron-chromium-nickel are being explored as alternative cladding materials to improve safety margins under severe accident conditions. Our research focuses on non-destructively investigating the oxidation behavior of the FeCrNi alloy "Alloy 33" using synchrotron-based methods. The evolution and structure of oxide layer formed in steam environments were characterized using X-ray diffraction, hard X-ray photoelectron spectroscopy, X-ray fluorescence methods and scanning electron microscopy. Our results demonstrate that a compact and continuous oxide scale was formed consisting of two layers, chromium oxide and spinel phase (FeCr2O4) oxides, wherein the concentration of the FeCr2O4 phase decreased from the surface to the bulk-oxide interface.

Porous Ni-Fe alloys as anode support for intermediate temperature solid oxide fuel cells: I. Fabrication, redox and thermal behaviors

NASA Astrophysics Data System (ADS)

Wang, Xin; Li, Kai; Jia, Lichao; Zhang, Qian; Jiang, San Ping; Chi, Bo; Pu, Jian; Jian, Li; Yan, Dong

2015-03-01

Porous Ni-Fe anode supports for intermediate solid oxide fuel cells are prepared by reducing the sintered NiO-(0-50 wt. %) Fe2O3 composites in H2, their microstructure, redox and thermal expansion/cycling characteristics are systematically investigated. The sintered NiO-Fe2O3 composites are consisted of NiO and NiFe2O4, and are fully reducible to porous metallic Ni-Fe alloys in H2 at temperatures between 600 and 750 °C. The porous structure contains pores in bimodal distribution with larger pores between the sintered particles and smaller ones inside the particles. The oxidation resistance of the Ni-Fe alloy anode supports at 600 and 750 °C is increased by the addition of Fe, their oxidation kinetics obeys a multistage parabolic law in the form of (Percentageweightgain /Specificsurfacearea) 2 =kp · t , where kp is the rate constant and t the oxidation time. The dimension of the Ni-Fe anode supports is slightly changed without disintegrating their structure, and Fe addition is beneficial to the redox stability. The TEC of the Ni-Fe alloy anode supports decreases with the increase of Fe content. The anode supports containing Fe is less stable in dimension during thermal cycles due to the continuous sintering, but the dimension change after thermal cycles is within 1%.

High-strain-rate superplasticity of the Al-Zn-Mg-Cu alloys with Fe and Ni additions

NASA Astrophysics Data System (ADS)

Kotov, A. D.; Mikhaylovskaya, A. V.; Borisov, A. A.; Yakovtseva, O. A.; Portnoy, V. K.

2017-09-01

During high-strain-rate superplastic deformation, superplasticity indices, and the microstructure of two Al-Zn-Mg-Cu-Zr alloys with additions of nickel and iron, which contain equal volume fractions of eutectic particles of Al3Ni or Al9FeNi, have been compared. It has been shown that the alloys exhibit superplasticity with 300-800% elongations at the strain rates of 1 × 10-2-1 × 10-1 s-1. The differences in the kinetics of alloy recrystallization in the course of heating and deformation at different temperatures and rates of the superplastic deformation, which are related to the various parameters of the particles of the eutectic phases, have been found. At strain rates higher than 4 × 10-2, in the alloy with Fe and Ni, a partially nonrecrystallized structure is retained up to material failure and, in the alloy with Ni, a completely recrystallized structure is formed at rates of up to 1 × 10-1 s-1.

Dependence of phase configurations, microstructures and magnetic properties of iron-nickel (Fe-Ni) alloy nanoribbons on deoxidization temperature in hydrogen

NASA Astrophysics Data System (ADS)

Jing, Panpan; Liu, Mengting; Pu, Yongping; Cui, Yongfei; Wang, Zhuo; Wang, Jianbo; Liu, Qingfang

2016-11-01

Iron-nickel (Fe-Ni) alloy nanoribbons were reported for the first time by deoxidizing NiFe2O4 nanoribbons, which were synthesized through a handy route of electrospinning followed by air-annealing at 450 °C, in hydrogen (H2) at different temperatures. It was demonstrated that the phase configurations, microstructures and magnetic properties of the as-deoxidized samples closely depended upon the deoxidization temperature. The spinel NiFe2O4 ferrite of the precursor nanoribbons were firstly deoxidized into the body-centered cubic (bcc) Fe-Ni alloy and then transformed into the face-centered cubic (fcc) Fe-Ni alloy of the deoxidized samples with the temperature increasing. When the deoxidization temperature was in the range of 300 ~ 500 °C, although each sample possessed its respective morphology feature, all of them completely reserved the ribbon-like structures. When it was further increased to 600 °C, the nanoribbons were evolved completely into the fcc Fe-Ni alloy nanochains. Additionally, all samples exhibited typical ferromagnetism. The saturation magnetization (Ms) firstly increased, then decreased, and finally increased with increasing the deoxidization temperature, while the coercivity (Hc) decreased monotonously firstly and then basically stayed unchanged. The largest Ms (~145.7 emu·g-1) and the moderate Hc (~132 Oe) were obtained for the Fe-Ni alloy nanoribbons with a mixed configuration of bcc and fcc phases.

Dependence of phase configurations, microstructures and magnetic properties of iron-nickel (Fe-Ni) alloy nanoribbons on deoxidization temperature in hydrogen.

PubMed

Jing, Panpan; Liu, Mengting; Pu, Yongping; Cui, Yongfei; Wang, Zhuo; Wang, Jianbo; Liu, Qingfang

2016-11-23

Iron-nickel (Fe-Ni) alloy nanoribbons were reported for the first time by deoxidizing NiFe 2 O 4 nanoribbons, which were synthesized through a handy route of electrospinning followed by air-annealing at 450 °C, in hydrogen (H 2 ) at different temperatures. It was demonstrated that the phase configurations, microstructures and magnetic properties of the as-deoxidized samples closely depended upon the deoxidization temperature. The spinel NiFe 2 O 4 ferrite of the precursor nanoribbons were firstly deoxidized into the body-centered cubic (bcc) Fe-Ni alloy and then transformed into the face-centered cubic (fcc) Fe-Ni alloy of the deoxidized samples with the temperature increasing. When the deoxidization temperature was in the range of 300 ~ 500 °C, although each sample possessed its respective morphology feature, all of them completely reserved the ribbon-like structures. When it was further increased to 600 °C, the nanoribbons were evolved completely into the fcc Fe-Ni alloy nanochains. Additionally, all samples exhibited typical ferromagnetism. The saturation magnetization (M s ) firstly increased, then decreased, and finally increased with increasing the deoxidization temperature, while the coercivity (H c ) decreased monotonously firstly and then basically stayed unchanged. The largest M s (~145.7 emu·g -1 ) and the moderate H c (~132 Oe) were obtained for the Fe-Ni alloy nanoribbons with a mixed configuration of bcc and fcc phases.

Surface Properties of a Nanocrystalline Fe-Ni-Nb-B Alloy After Neutron Irradiation

NASA Astrophysics Data System (ADS)

Pavùk, Milan; Sitek, Jozef; Sedlačková, Katarína

2014-09-01

The effect of neutron radiation on the surface properties of the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy was studied. Firstly, amorphous (Fe0.25Ni0.75)81Nb7B12 ribbon was brought by controlled annealing to the nanocrystalline state. After annealing, the samples of the nanocrystalline ribbon were irradiated in a nuclear reactor with neutron fluences of 1×1016cm-2 and 1 × 1017cm-2 . By utilizing the magnetic force microscopy (MFM), topography and a magnetic domain structure were recorded at the surface of the ribbon-shaped samples before and after irradiation with neutrons. The results indicate that in terms of surface the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy is radiation-resistant up to a neutron fluence of 1 × 1017cm-2 . The changes in topography observed for both irradiated samples are discussed

Microstructure and corrosion properties of CrMnFeCoNi high entropy alloy coating

NASA Astrophysics Data System (ADS)

Ye, Qingfeng; Feng, Kai; Li, Zhuguo; Lu, Fenggui; Li, Ruifeng; Huang, Jian; Wu, Yixiong

2017-02-01

Equimolar CrMnFeCoNi high entropy alloy (HEA) is one of the most notable single phase multi-component alloys up-to-date with promising mechanical properties at cryogenic temperatures. However, the study on the corrosion behavior of CrMnFeCoNi HEA coating has still been lacking. In this paper, HEA coating with a nominal composition of CrMnFeCoNi is fabricated by laser surface alloying and studied in detail. Microstructure and chemical composition are determined by X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) are used to investigate the corrosion behavior. The coating forms a simple FCC phase with an identical dendritic structure composed of Fe/Co/Ni-rich dendrites and Mn/Ni-rich interdendrites. Both in 3.5 wt.% NaCl solution and 0.5 M sulfuric acid the coating exhibits nobler corrosion resistance than A36 steel substrate and even lower icorr than 304 stainless steel (304SS). EIS plots coupled with fitted parameters reveal that a spontaneous protective film is formed and developed during immersion in 0.5 M sulfuric acid. The fitted Rt value reaches its maximum at 24 h during a 48 h' immersion test, indicating the passive film starts to break down after that. EDS analysis conducted on a corroded surface immersed in 0.5 M H2SO4 reveals that corrosion starts from Cr-depleted interdendrites.

Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application

DOEpatents

Muralidharan, Govindarajan

2017-09-05

An Fe--Ni--Cr alloy is composed essentially of, in terms of wt. %: 2.4 to 3.7 Al, up to 1.05 Co, 14.8 to 15.9 Cr, 25 to 36 Fe, up to 1.2 Hf, up to 4 Mn, up to 0.6 Mo, up to 2.2 Nb, up to 1.05 Ta, 1.9 to 3.6 Ti, up to 0.08 W, up to 0.03 Zr, 0.18 to 0.27 C, up to 0.0015 N, balance Ni, wherein, in terms of atomic percent: 8.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.11.5, 0.53.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.65, and 0.16.ltoreq.Cr/(Fe+Ni+Cr+Mn).ltoreq.0.21, the alloy being essentially free of Cu, Si, and V.

Metal elution from Ni- and Fe-based alloy reactors under hydrothermal conditions.

PubMed

Faisal, Muhammad; Quitain, Armando T; Urano, Shin-Ya; Daimon, Hiroyuki; Fujie, Koichi

2004-05-20

Elution of metals from Ni- and Fe-based alloy (i.e. Inconel 625 and SUS 316) under hydrothermal conditions was investigated. Results showed that metals could be eluted even in a short contact time. At subcritical conditions, a significant amount of Cr was extracted from SUS 316, while only traces of Ni, Fe, Mo, and Mn were eluted. In contrast, Ni was removed in significant amounts compared to Cr when Inconel 625 was tested. Several factors including temperature and contact time were found to affect elution behavior. The presence of air in the fluid even promoted elution under subcritical conditions.

Statistical theory of diffusion in concentrated bcc and fcc alloys and concentration dependencies of diffusion coefficients in bcc alloys FeCu, FeMn, FeNi, and FeCr

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaks, V. G.; Khromov, K. Yu., E-mail: khromov-ky@nrcki.ru; Pankratov, I. R.

2016-07-15

The statistical theory of diffusion in concentrated bcc and fcc alloys with arbitrary pairwise interatomic interactions based on the master equation approach is developed. Vacancy–atom correlations are described using both the second-shell-jump and the nearest-neighbor-jump approximations which are shown to be usually sufficiently accurate. General expressions for Onsager coefficients in terms of microscopic interatomic interactions and some statistical averages are given. Both the analytical kinetic mean-field and the Monte Carlo methods for finding these averages are described. The theory developed is used to describe sharp concentration dependencies of diffusion coefficients in several iron-based alloy systems. For the bcc alloys FeCu,more » FeMn, and FeNi, we predict the notable increase of the iron self-diffusion coefficient with solute concentration c, up to several times, even though values of c possible for these alloys do not exceed some percent. For the bcc alloys FeCr at high temperatures T ≳ 1400 K, we show that the very strong and peculiar concentration dependencies of both tracer and chemical diffusion coefficients observed in these alloys can be naturally explained by the theory, without invoking exotic models discussed earlier.« less

Fluorescence x-ray absorption fine structure studies of Fe-Ni-S and Fe-Ni-Si melts to 1600 K

NASA Astrophysics Data System (ADS)

Manghnani, M. H.; Hong, X.; Balogh, J.; Amulele, G.; Sekar, M.; Newville, M.

2008-04-01

We report NiK -edge fluorescence x-ray absorption fine structure spectra (XAFS) for Fe0.75Ni0.05S0.20 and Fe0.75Ni0.05Si0.20 ternary alloys from room temperature up to 1600 K. A high-temperature furnace designed for these studies incorporates two x-ray transparent windows and enables both a vertical orientation of the molten sample and a wide opening angle, so that XAFS can be measured in the fluorescence mode with a detector at 90° with respect to the incident x-ray beam. An analysis of the Ni XAFS data for these two alloys indicates different local structural environments for Ni in Fe0.75Ni0.05S0.20 and Fe0.75Ni0.05Si0.20 melts, with more Ni-Si coordination than Ni-S coordination persisting from room temperature through melting. These results suggest that light elements such as S and Si may impact the structural and chemical properties of Fe-Ni alloys with a composition similar to the earth’s core.

He behavior in Ni and Ni-based equiatomic solid solution alloy

NASA Astrophysics Data System (ADS)

Yan, Zhanfeng; Liu, Shaoshuai; Xia, Songqin; Zhang, Yong; Wang, Yugang; Yang, Tengfei

2018-07-01

In the current work, pure nickel (99.99 wt.%) and Ni-containing single phase equiatomic solid solution alloy Fe-Co-Cr-Ni were irradiated with 190 keV He ions at room temperature with different fluences and He behavior in both materials are compared. At 1 × 1017 cm-2, TEM observation reveals that only isolated and small He bubbles (1-2 nm) are formed in Fe-Co-Cr-Ni alloy while many small suspected "string"-like He bubbles are observed in nickel at the concentration peak region (5.5 at.%). When the fluence is increased to 5 × 1017 cm-2, average bubble size in nickel increases to ∼8 nm which is almost equal to that in Fe-Co-Cr-Ni, but a higher bubble density is observed in nickel. At the highest dose of 1 × 1018 cm-2, numerous surface blisters and exfoliations occur in nickel which are consistent with TEM observation, while the Fe-Co-Cr-Ni alloy only shows a slight surface blister. Bubble coarsening upon annealing at 500 °C (2 h) is observed at 5 × 1017 cm-2 in both alloys, but a significant larger bubble growth is observed in nickel, suggesting a relatively better resistance to He bubble growth for Fe-Co-Cr-Ni alloy.

Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems

PubMed Central

Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

2016-01-01

In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy. PMID:26923713

Effect of one-step recrystallization on the grain boundary evolution of CoCrFeMnNi high entropy alloy and its subsystems.

PubMed

Chen, Bo-Ru; Yeh, An-Chou; Yeh, Jien-Wei

2016-02-29

In this study, the grain boundary evolution of equiatomic CoCrFeMnNi, CoCrFeNi, and FeCoNi alloys after one-step recrystallization were investigated. The special boundary fraction and twin density of these alloys were evaluated by electron backscatter diffraction analysis. Among the three alloys tested, FeCoNi exhibited the highest special boundary fraction and twin density after one-step recrystallization. The special boundary increment after one-step recrystallization was mainly affected by grain boundary velocity, while twin density was mainly affected by average grain boundary energy and twin boundary energy.

Supergene neoformation of Pt-Ir-Fe-Ni alloys: multistage grains explain nugget formation in Ni-laterites

NASA Astrophysics Data System (ADS)

Aiglsperger, Thomas; Proenza, Joaquín A.; Font-Bardia, Mercè; Baurier-Aymat, Sandra; Galí, Salvador; Lewis, John F.; Longo, Francisco

2017-10-01

Ni-laterites from the Dominican Republic host rare but extremely platinum-group element (PGE)-rich chromitites (up to 17.5 ppm) without economic significance. These chromitites occur either included in saprolite (beneath the Mg discontinuity) or as `floating chromitites' within limonite (above the Mg discontinuity). Both chromitite types have similar iridium-group PGE (IPGE)-enriched chondrite normalized patterns; however, chromitites included in limonite show a pronounced positive Pt anomaly. Investigation of heavy mineral concentrates, obtained via hydroseparation techniques, led to the discovery of multistage PGE grains: (i) Os-Ru-Fe-(Ir) grains of porous appearance are overgrown by (ii) Ni-Fe-Ir and Ir-Fe-Ni-(Pt) phases which are overgrown by (iii) Pt-Ir-Fe-Ni mineral phases. Whereas Ir-dominated overgrowths prevail in chromitites from the saprolite, Pt-dominated overgrowths are observed within floating chromitites. The following formation model for multistage PGE grains is discussed: (i) hypogene platinum-group minerals (PGM) (e.g. laurite) are transformed to secondary PGM by desulphurization during serpentinization; (ii) at the stages of serpentinization and/or at the early stages of lateritization, Ir is mobilized and recrystallizes on porous surfaces of secondary PGM (serving as a natural catalyst) and (iii) at the late stages of lateritization, biogenic mediated neoformation (and accumulation) of Pt-Ir-Fe-Ni nanoparticles occurs. The evidence presented in this work demonstrates that in situ growth of Pt-Ir-Fe-Ni alloy nuggets of isometric symmetry is possible within Ni-laterites from the Dominican Republic.

High-temperature oxidation of advanced FeCrNi alloy in steam environments

DOE PAGES

Elbakhshwan, Mohamed S.; Gill, Simerjeet K.; Rumaiz, Abdul K.; ...

2017-07-04

Alloys of iron-chromium-nickel are being explored as alternative cladding materials to improve safety margins under severe accident conditions. Here, our research focuses on non-destructively investigating the oxidation behavior of the FeCrNi alloy “Alloy 33” using synchrotron-based methods. The evolution and structure of oxide layer formed in steam environments were characterized using X-ray diffraction, hard X-ray photoelectron spectroscopy, X-ray fluorescence methods and scanning electron microscopy. In conclusion, our results demonstrate that a compact and continuous oxide scale was formed consisting of two layers, chromium oxide and spinel phase (FeCr 2O 4) oxides, wherein the concentration of the FeCr 2O 4 phasemore » decreased from the surface to the bulk-oxide interface.« less

Contrast studies of the process optimization and characterization of shielding fabric by amorphous Ni-Fe-P and Ni-P alloy

NASA Astrophysics Data System (ADS)

Yao, Kai; Wu, Xueyan; An, Zhentao

2017-01-01

A flexible shielding fabric with dense uniform coating was prepared after electrical deposition of amorphous Ni-Fe-P and Ni-P alloy on copper-coated polyethylene terephthalate (PET) fabric. The effects of coating composition and the deposition rate were discussed by the current density, temperature and pH value. The morphology, composition, and structure of coating were analyzed by SEM, EDS, and XRD characterizations. The EMI shielding effectiveness and corrosion resistance were also tested. The results fabric possesses dense, smooth, and uniform coating, when the processing conditions are 60°C, pH=1.5, and current density =8.7A/dm2. The coating fabric consists of amorphous Ni-Fe-P alloy with 16.62% P (weight percent), which has excellent of corrosion resistance. By contrast the EMI shielding effectiveness of amorphous Ni-Fe-P was better than amorphous Ni-P. The EMI shielding effectiveness of this coated fabric achieves 69.20dB-80.30dB in a broad frequency range between 300 kHz˜1.5 GHz.

Exchange interactions and magnetocaloric effects of the Heusler alloys Ni-Mn-In-R (R = Fe, Co)

NASA Astrophysics Data System (ADS)

Li, Yan-Ru; Su, Hui-Ling; Sun, Ji-Bing; Li, Ying

2018-05-01

The magnetic interactions and magnetocaloric effects in Ni2Mn1.4In0.6‑xRx (x = 0-0.2) (R = Fe, Co) Heusler alloys are investigated by the first-principles and Monte Carlo method. The ab initio calculations provide a basic understanding of the competition of ferromagnetic and antiferromagnetic interactions due to the chemical disorder of the alloy compositions. The thermodynamic properties including magnetization, specific heat and magnetic entropy change are calculated by the finite-temperature Monte Carlo simulations using the exchange couplings and magnetic moments from ab initio calculation as input parameters. The results show that the Fe or Co doping in Ni2Mn1.4In0.6 leads to an increase of magnetic moment and magnetic entropy change but a decrease of magnetic transition temperature with the increase in the Fe or Co contents. This indicates that the transition temperature and magnetocaloric properties of Ni2Mn1.4In0.6 alloy can be tuned by substituting In atom by Fe or Co with different contents.

Microstructure, Texture, and Mechanical Behavior of As-cast Ni-Fe-W Matrix Alloy

NASA Astrophysics Data System (ADS)

Rao, A. Sambasiva; Manda, Premkumar; Mohan, M. K.; Nandy, T. K.; Singh, A. K.

2018-04-01

This article describes the tensile properties, flow, and work-hardening behavior of an experimental alloy 53Ni-29Fe-18W in as-cast condition. The microstructure of the alloy 53Ni-29Fe-18W displays single phase (fcc) in as-cast condition along with typical dendritic features. The bulk texture of the as-cast alloy reveals the triclinic sample symmetry and characteristic nature of coarse-grained materials. The alloy exhibits maximum strength ( σ YS and σ UTS) values along the transverse direction. The elongation values are maximum and minimum along the transverse and longitudinal directions, respectively. Tensile fracture surfaces of both the longitudinal and transverse samples display complete ductile fracture features. Two types of slip lines, namely, planar and intersecting, are observed in deformed specimens and the density of slip lines increases with increasing the amount of deformation. The alloy displays moderate in-plane anisotropy ( A IP) and reasonably low anisotropic index ( δ) values, respectively. The instantaneous or work-hardening rate curves portray three typical stages (I through III) along both the longitudinal and transverse directions. The alloy exhibits dislocation-controlled strain hardening during tensile testing, and slip is the predominant deformation mechanism.

Microstructures and mechanical properties of compositionally complex Co-free FeNiMnCr 18 FCC solid solution alloy

DOE PAGES

Wu, Z.; Bei, H.

2015-07-01

Recently, a structurally-simple but compositionally-complex FeNiCoMnCr high entropy alloy was found to have excellent mechanical properties (e.g., high strength and ductility). To understand the potential of using high entropy alloys as structural materials for advanced nuclear reactor and power plants, it is necessary to have a thorough understanding of their structural stability and mechanical properties degradation under neutron irradiation. Furthermore, this requires us to develop a similar model alloy without Co because material with Co will make post-neutron-irradiation testing difficult due to the production of the 60Co radioisotope. In order to achieve this goal, a FCC-structured single-phase alloy with amore » composition of FeNiMnCr 18 was successfully developed. This near-equiatomic FeNiMnCr 18 alloy has good malleability and its microstructure can be controlled by thermomechanical processing. By rolling and annealing, the as-cast elongated-grained-microstructure is replaced by homogeneous equiaxed grains. The mechanical properties (e.g., strength and ductility) of the FeNiMnCr 18 alloy are comparable to those of the equiatomic FeNiCoMnCr high entropy alloy. Both strength and ductility increase with decreasing deformation temperature, with the largest difference occurring between 293 and 77 K. Extensive twin-bands which are bundles of numerous individual twins are observed when it is tensile-fractured at 77 K. No twin bands are detected by EBSD for materials deformed at 293 K and higher. Ultimately the unusual temperature-dependencies of UTS and uniform elongation could be caused by the development of the dense twin substructure, twin-dislocation interactions and the interactions between primary and secondary twinning systems which result in a microstructure refinement and hence cause enhanced strain hardening and postponed necking.« less

Alloying Behavior and Properties of FeSiBAlNiCo x High Entropy Alloys Fabricated by Mechanical Alloying and Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Wang, Wen; Li, Boyu; Zhai, Sicheng; Xu, Juan; Niu, Zuozhe; Xu, Jing; Wang, Yan

2018-02-01

In this paper, FeSiBAlNiCo x (x = 0.2, 0.8) high-entropy alloy (HEA) powders were fabricated by mechanical alloying process, and the powders milled for 140 h were sintered by spark plasma sintering (SPS) technique. The microstructures and properties of as-milled powders and as-sintered samples were investigated. The results reveal that the final milling products (140 h) of both sample powders present the fully amorphous structure. The increased Co contents obviously enhance the glass forming ability and thermal stability of amorphous HEA powders, which are reflected by the shorter formation time of fully amorphous phase and the higher onset crystallization temperature, respectively. According to coercivity, the as-milled FeSiBAlNiCo x (x = 0.2, 0.8) powders (140 h) are the semi-hard magnetic materials. FeSiBAlNiCo0.8 HEA powders possess the highest saturation magnetization and largest remanence ratio. The SPS-ed products of both bulk HEAs are composed of body-centered cubic solid solution, and FeSi and FeB intermetallic phases. They possess the high relative density above 97% and excellent microhardness exceeding 1150 HV. The as-sintered bulks undergo the remarkable increase in saturation magnetization compared with the as-milled state. The SPS-ed FeSiBAlNiCo0.8 HEA exhibits the soft magnetic properties. The electrochemical corrosion test is carried out in 3.5% NaCl solution. The SPS-ed FeSiBAlNiCo0.2 HEA reveals the better passivity with low passive current density, and the higher pitting resistance with wide passive region.

Phase Equilibria of the Fe-Ni-Sn Ternary System at 270°C

NASA Astrophysics Data System (ADS)

Huang, Tzu-Ting; Lin, Shih-Wei; Chen, Chih-Ming; Chen, Pei Yu; Yen, Yee-Wen

2016-12-01

The Fe-42 wt.% Ni alloy, also known as a 42 invar alloy (Alloy 42), is used as a lead-frame material because its thermal expansion coefficient is much closer to Si substrate than Cu or Ni substrates. In order to enhance the wettability between the substrate and solder, the Sn layer was commonly electroplated onto the Alloy 42 surface. A clear understanding of the phase equilibria of the Fe-Ni-Sn ternary system is necessary to ensure solder-joint reliability between Sn and Fe-Ni alloys. To determine the isothermal section of the Fe-Ni-Sn ternary system at 270°C, 26 Fe-Ni-Sn alloys with different compositions were prepared. The experimental results confirmed the presence of the Fe3Ni and FeNi phases at 270°C. Meanwhile, it observed that the isothermal section of the Fe-Ni-Sn ternary system was composed of 11 single-phase regions, 19 two-phase regions and nine tie-triangles. Moreover, no ternary compounds were found in the Fe-Ni-Sn system at 270°C.

Atomic scale study of grain boundary segregation before carbide nucleation in Ni-Cr-Fe Alloys

NASA Astrophysics Data System (ADS)

Li, Hui; Xia, Shuang; Liu, Wenqing; Liu, Tingguang; Zhou, Bangxin

2013-08-01

Three dimensional chemical information concerning grain boundary segregation before carbide nucleation was characterized by atom probe tomography in two Ni-Cr-Fe alloys which were aged at 500 °C for 0.5 h after homogenizing treatment. B, C and Si atoms segregation at grain boundary in Alloy 690 was observed. B, C, N and P atoms segregation at grain boundary in 304 austenitic stainless steel was observed. C atoms co-segregation with Cr atoms at the grain boundaries both in Alloy 690 and 304 austenitic stainless steel was found, and its effect on the carbide nucleation was discussed. The amount of each segregated element at grain boundaries in the two Ni-Cr-Fe alloys were analyzed quantitatively. Comparison of the grain boundary segregation features of the two Ni-Cr-Fe alloys were carried out based on the experimental results. The impurity and solute atoms segregate inhomogeneously in the same grain boundary both in 304 SS and Alloy 690. The grain boundary segregation tendencies (Sav) are B (11.8 ± 1.4) > P (5.4 ± 1.4) > N (4.7 ± 0.3) > C (3.7 ± 0.4) in 304 SS, and B (6.9 ± 0.9) > C (6.7 ± 0.4) > Si (1.5 ± 0.2) in Alloy 690. Cr atoms may co-segregate with C atoms at grain boundaries before carbide nucleation at the grain boundaries both in 304 SS and Alloy 690. Ni atoms generally deplete at grain boundary both in 304 SS and Alloy 690. The literature shows that the Ni atoms may co-segregate with P atoms at grain boundaries [28], but the P atoms segregation do not leads to Ni segregation in the current study. In the current study, Fe atoms may segregate or deplete at grain boundary in Alloy 690. But Fe atoms generally deplete at grain boundary in 304 SS. B atoms have the strongest grain boundary segregation tendency both in 304 SS and Alloy 690. The grain boundary segregation tendency and Gibbs free energy of B in 304 SS is higher than in Alloy 690. C atoms are easy to segregate at grain boundaries both in 304 SS and Alloy 690. The grain boundary segregation

Study of the effects of implantation on the high Fe-Ni-Cr and Ni-Cr-Al alloys

NASA Technical Reports Server (NTRS)

Ribarsky, M. W.

1985-01-01

A theoretical study of the effects of implantation on the corrosion resistance of Fe-Ni-Cr and Ni-Cr-Al alloys was undertaken. The purpose was to elucidate the process by which corrosion scales form on alloy surfaces. The experiments dealt with Ni implanted with Al, exposed to S at high temperatures, and then analyzed using scanning electron microscopy, scanning Auger spectroscopy and X-ray fluorescence spectroscopy. Pair bonding and tight-binding models were developed to study the compositions of the alloys and as a result, a new surface ordering effect was found which may exist in certain real alloys. With these models, the behavior of alloy constituents in the presence of surface concentrations of O or S was also studied. Improvements of the models to take into account the important effects of long- and short-range ordering were considered. The diffusion kinetics of implant profiles at various temperatures were investigated, and it was found that significant non-equilibrium changes in the profiles can take place which may affect the implants' performance in the presence of surface contaminants.

The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO 3 Fe 3Al, Co 3Al, and Ni 3Al based intermetallic phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO 3 Fe 3Al, Co 3Al and Ni 3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO 3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe 3Al and Co 3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO 3 Fe 3Al, Co 3Al, and Ni 3Al based intermetallic phases

DOE PAGES

Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

2014-11-07

Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO 3 Fe 3Al, Co 3Al and Ni 3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO 3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe 3Al and Co 3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

Weldability of a high entropy CrMnFeCoNi alloy

DOE PAGES

Wu, Zhenggang; David, Stan A.; Feng, Zhili; ...

2016-07-19

We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ ofmore » the tested alloy.« less

Note: Erosion of W-Ni-Fe and W-Cu alloy electrodes in repetitive spark gaps.

PubMed

Wu, Jiawei; Han, Ruoyu; Ding, Weidong; Qiu, Aici; Tang, Junping

2018-02-01

A pair of W-Ni-Fe and W-Cu electrodes were tested under 100 kA level pulsed currents for 10 000 shots, respectively. Surface roughness and morphology characteristics of the two pairs of electrodes were obtained and compared. Experimental results indicated cracks divided the W-Cu electrode surface to polygons while the W-Ni-Fe electrode surface remained as a whole with pits and protrusions. Accordingly, the surface roughness of W-Ni-Fe electrodes increased to ∼3 μm while that of W-Cu electrodes reached ∼7 μm at the end of the test. The results reveal that the W-Ni-Fe alloy has a better erosion resistance and potential to be further applied in spark gaps.

Low Temperature Diffusion Transformations in Fe-Ni-Ti Alloys During Deformation and Irradiation

NASA Astrophysics Data System (ADS)

Sagaradze, Victor; Shabashov, Valery; Kataeva, Natalya; Kozlov, Kirill; Arbuzov, Vadim; Danilov, Sergey; Ustyugov, Yury

2018-03-01

The deformation-induced dissolution of Ni3Ti intermetallics in the matrix of austenitic alloys of Fe-36Ni-3Ti type was revealed in the course of their cascade-forming neutron irradiation and cold deformation at low temperatures via employment of Mössbauer method. The anomalous deformation-related dissolution of the intermetallics has been explained by the migration of deformation-induced interstitial atoms from the particles into a matrix in the stress field of moving dislocations. When rising the deformation temperature, this process is substituted for by the intermetallics precipitation accelerated by point defects. A calculation of diffusion processes has shown the possibility of the realization of the low-temperature diffusion of interstitial atoms in configurations of the crowdions and dumbbell pairs at 77-173 K. The existence of interstitial atoms in the Fe-36Ni alloy irradiated by electrons or deformed at 77 K was substantiated in the experiments of the electrical resistivity measurements.

X-ray absorption investigation of local structural disorder in Ni 1-xFe x (x=0.10, 0.20, 0.35, and 0.50) alloys

DOE PAGES

Zhang, Fuxiang X.; Jin, Ke; Zhao, Shijun; ...

2017-04-27

Defect energetics in structural materials has long been recognized to be affected by specific alloy compositions. Significantly enhanced radiation resistance has recently been observed in concentrated solid-solution alloys. However, the link between local structural disorder and modified defect dynamics in solid solutions remains unclear. To reveal the atomic-level lattice distortion, the local structures of Ni and Fe in Ni 1-xFe x (x=0.1, 0.2, 0.35 and 0.5) solid solution alloys were measured with extended X-ray absorption fine structure (EXAFS) technique. The lattice constant and the first-neighbor distances increase with the increase of Fe content in the solid solutions. EXAFS measurements havemore » revealed that the bond length of Fe with surrounding atoms is 0.01-0.03 larger than that of Ni in the alloy systems. Debye-Waller factor of the Fe-Fe bonds in all the systems is also slightly larger than that of the Ni-Ni bond. EXAFS fitting suggests that the local structural disorder is enhanced with the addition of Fe elements in the solid solution. The local bonding environments from ab initio calculation are in good agreement with the experimental results, which suggest that the Fe has a larger first-neighbor bonding distance than that of Ni, and thus Ni atom inside the Ni-Fe solid solution alloys undergoes compressive strain.« less

X-ray absorption investigation of local structural disorder in Ni 1-xFe x (x=0.10, 0.20, 0.35, and 0.50) alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fuxiang X.; Jin, Ke; Zhao, Shijun

Defect energetics in structural materials has long been recognized to be affected by specific alloy compositions. Significantly enhanced radiation resistance has recently been observed in concentrated solid-solution alloys. However, the link between local structural disorder and modified defect dynamics in solid solutions remains unclear. To reveal the atomic-level lattice distortion, the local structures of Ni and Fe in Ni 1-xFe x (x=0.1, 0.2, 0.35 and 0.5) solid solution alloys were measured with extended X-ray absorption fine structure (EXAFS) technique. The lattice constant and the first-neighbor distances increase with the increase of Fe content in the solid solutions. EXAFS measurements havemore » revealed that the bond length of Fe with surrounding atoms is 0.01-0.03 larger than that of Ni in the alloy systems. Debye-Waller factor of the Fe-Fe bonds in all the systems is also slightly larger than that of the Ni-Ni bond. EXAFS fitting suggests that the local structural disorder is enhanced with the addition of Fe elements in the solid solution. The local bonding environments from ab initio calculation are in good agreement with the experimental results, which suggest that the Fe has a larger first-neighbor bonding distance than that of Ni, and thus Ni atom inside the Ni-Fe solid solution alloys undergoes compressive strain.« less

Structure, magnetic ordering, and spin filtering efficiency of NiFe{sub 2}O{sub 4}(111) ultrathin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matzen, S.; Moussy, J.-B., E-mail: jean-baptiste.moussy@cea.fr; Wei, P.

2014-05-05

NiFe{sub 2}O{sub 4}(111) ultrathin films (3–5 nm) have been grown by oxygen-assisted molecular beam epitaxy and integrated as effective spin-filter barriers. Structural and magnetic characterizations have been performed in order to investigate the presence of defects that could limit the spin filtering efficiency. These analyses have revealed the full strain relaxation of the layers with a cationic order in agreement with the inverse spinel structure but also the presence of antiphase boundaries. A spin-polarization up to +25% has been directly measured by the Meservey-Tedrow technique in Pt(111)/NiFe{sub 2}O{sub 4}(111)/γ-Al{sub 2}O{sub 3}(111)/Al tunnel junctions. The unexpected positive sign and relatively small valuemore » of the spin-polarization are discussed, in comparison with predictions and previous indirect tunnelling magnetoresistance measurements.« less

Phase Transformation and Aging Behavior of Al0.5CoCrFeNiSi0.2 High-Entropy Alloy

NASA Astrophysics Data System (ADS)

Zhang, C.; Wu, G. F.; Dai, P. Q.

2015-05-01

An Al0.5CoCrFeNiSi0.2 high-entropy alloy was prepared by vacuum arc melting. The alloy was aged from 700 to 1100 °C. The effects of aging on the phase transformation and mechanical performances were explored. The as-cast alloy showed a dendritic (DR) microstructure. The DR region was an Fe,Cr-rich FCC phase, while the interdendritic (ID) region was a spinodal structure composed of Fe,Cr-rich BCC (A2) and Ni,Al-rich BCC (B2) phases. At aging temperatures between 700 and 900 °C, the Fe,Cr-rich BCC (A2) phase in the ID region transformed into σ and Fe,Cr-rich FCC phases. Meanwhile, some Ni,Al-rich FCC phase particles precipitated from the DR region. During aging at 1100 °C, the DR microstructure disappeared, and a microstructure composed of Fe,Cr-rich FCC and Ni,Al-rich BCC (B2) phases both possessing a lamellar shape was developed. The alloy exhibited evident hardening and lower tensile strain when the aging temperature was lower than 1000 °C, which was mainly attributed to the generation of the σ phase in the ID region. However, a contrasting behavior was observed when the aging temperature was higher than 1000 °C, which was attributed to the redissolution of the σ phase and the microstructure coarsening.

Stress Corrosion Cracking of Ni-Fe-Cr Alloys Relevant to Nuclear Power Plants

NASA Astrophysics Data System (ADS)

Persaud, Suraj

Stress corrosion cracking (SCC) of Ni-Fe-Cr alloys and weld metals was investigated in simulated environments representative of high temperature water used in the primary and secondary circuits of nuclear power plants. The mechanism of primary water SCC (PWSCC) was studied in Alloys 600, 690, 800 and Alloy 82 dissimilar metal welds using the internal oxidation model as a guide. Initial experiments were carried out in a 480°C hydrogenated steam environment considered to simulate high temperature reducing primary water. Ni alloys underwent classical internal oxidation intragranularly resulting in the expulsion of the solvent metal, Ni, to the surface. Selective intergranular oxidation of Cr in Alloy 600 resulted in embrittlement, while other alloys were resistant owing to their increased Cr contents. Atom probe tomography was used to determine the short-circuit diffusion path used for Ni expulsion at a sub-nanometer scale, which was concluded to be oxide-metal interfaces. Further exposures of Alloys 600 and 800 were done in 315°C simulated primary water and intergranular oxidation tendency was comparable to 480°C hydrogenated steam. Secondary side work involved SCC experiments and electrochemical measurements, which were done at 315°C in acid sulfate solutions. Alloy 800 C-rings were found to undergo acid sulfate SCC (AcSCC) to a depth of up to 300 microm in 0.55 M sulfate solution at pH 4.3. A focused-ion beam was used to extract a crack tip from a C-ring and high resolution analytical electron microscopy revealed a duplex oxide structure and the presence of sulfur. Electrochemical measurements were taken on Ni alloys to complement crack tip analysis; sulfate was concluded to be the aggressive anion in mixed sulfate and chloride systems. Results from electrochemical measurements and crack tip analysis suggested a slip dissolution-type mechanism to explain AcSCC in Ni alloys.

Investigation of phase stability of novel equiatomic FeCoNiCuZn based-high entropy alloy prepared by mechanical alloying

NASA Astrophysics Data System (ADS)

Soni, Vinay Kumar; Sanyal, S.; Sinha, S. K.

2018-05-01

The present work reports the structural and phase stability analysis of equiatomic FeCoNiCuZn High entropy alloy (HEA) systems prepared by mechanical alloying (MA) method. In this research effort some 1287 alloy combinations were extensively studied to arrive at most favourable combination. FeCoNiCuZn based alloy system was selected on the basis of physiochemical parameters such as enthalpy of mixing (ΔHmix), entropy of mixing (ΔSmix), atomic size difference (ΔX) and valence electron concentration (VEC) such that it fulfils the formation criteria of stable multi component high entropy alloy system. In this context, we have investigated the effect of novel alloying addition in view of microstructure and phase formation aspect. XRD plots of the MA samples shows the formation of stable solid solution with FCC (Face Cantered Cubic) after 20 hr of milling time and no indication of any amorphous or intermetallic phase formation. Our results are in good agreement with calculation and analysis done on the basis of physiochemical parameters during selection of constituent elements of HEA.

Microstructure and mechanical properties of Ni and Fe-base boride-dispersion-strengthened microcrystalline alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wade, C.S.; Park, H.G.; Hoagland, R.G.

This paper considers the relation between microstructure and mechanical properties of two Ni-base and two Fe-base Boride-Dispersion-Strengthened Microcrystalline (BDSM) alloys. In these very fine grained materials the borides were primarily Cr, Mo, and MoFe in a fcc matrix in three of the alloys, and a bcc in one of the Fe-base alloys. Strength data and resistance to stress corrosion cracking are reported and, in the latter case, extraordinary resistance to SCC in NaCl, Na{sub 2}S{sub 2}O{sub 3} and boiling MgCl{sub 2} environments was observed in every case. The fcc BDSM alloys also demonstrated excellent thermal stability in terms of strengthmore » and fracture roughness up to 1000 C. The bcc alloy suffered severe loss of toughness. The fracture mode involved ductile rupture in all alloys and they display a reasonably linear correlation between K{sub Ic} and the square root of particle spacing.« less

Nano-twin Mediated Plasticity in Carbon-containing FeNiCoCrMn High Entropy Alloys

DOE PAGES

Wu, Zhenggang; Bei, Hongbin; Parish, Chad M

2015-06-14

Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. Moreover, the effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. We found that these materials canmore » be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (~70% at 77 K and ~40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys.« less

Microstructure and Tribological Properties of AlCoCrFeNiTi0.5 High-Entropy Alloy in Hydrogen Peroxide Solution

NASA Astrophysics Data System (ADS)

Yu, Y.; Liu, W. M.; Zhang, T. B.; Li, J. S.; Wang, J.; Kou, H. C.; Li, J.

2014-01-01

Microstructure and tribological properties of an AlCoCrFeNiTi0.5 high-entropy alloy in high-concentration hydrogen peroxide solution were investigated in this work. The results show that the sigma phase precipitates and the content of bcc2 decrease during the annealing process. Meanwhile, the complex construction of the interdendrite region changes into simple isolated-island shape, and much more spherical precipitates are formed. Those changes of microstructure during the annealing process lead to the increase of hardness of this alloy. In the testing conditions, the AlCoCrFeNiTi0.5 alloy shows smoother worn surfaces and steadier coefficient of friction curves than does the 1Cr18Ni9Ti stainless steel, and SiC ceramic preserves better wear resistance than ZrO2 ceramic. After annealing, the wear resistance of the AlCoCrFeNiTi0.5 alloy increases coupled with SiC counterface but decreases with ZrO2 counterface.

High-Temperature Oxidation Behavior of Al-Co-Cr-Ni-(Fe or Si) Multicomponent High-Entropy Alloys

NASA Astrophysics Data System (ADS)

Butler, T. M.; Alfano, J. P.; Martens, R. L.; Weaver, M. L.

2015-01-01

High-entropy alloys (HEAs) are a class of alloys that are being considered for a number of applications. In the present study, the microstructures and 1050°C oxidation behaviors of two HEAs, Al10Cr22.5Co22.5Ni22.5Fe22.5 (at.%) and Al20Cr25Co25Ni25Si5 have been investigated along with Al15Cr10Co35Ni35Si5, which is a high-temperature shape-memory alloy. Oxide formation occurred via selective oxidation in a manner that was consistent with the oxide formation model devised by Giggins and Pettit for model Ni-Cr-Al alloys. The lower Al content alloy formed an external Cr2O3 scale and an internal subscale consisting of Al2O3 and AlN precipitates. The higher Al content alloys exhibited smaller mass gains and formed external Al2O3 scales without any internal oxidation of the alloys.

Tailoring the composition of ultrathin, ternary alloy PtRuFe nanowires for the methanol oxidation reaction and formic acid oxidation reaction

DOE PAGES

Scofield, Megan E.; Koenigsmann, Christopher; Wang, Lei; ...

2014-11-25

In the search for alternatives to conventional Pt electrocatalysts, we have synthesized ultrathin, ternary PtRuFe nanowires (NW), possessing different chemical compositions in order to probe their CO tolerance as well as electrochemical activity as a function of composition for both (i) the methanol oxidation reaction (MOR) and (ii) the formic acid oxidation reaction (FAOR). As-prepared ‘multifunctional’ ternary NW catalysts exhibited both higher MOR and FAOR activity as compared with binary Pt₇Ru₃ NW, monometallic Pt NW, and commercial catalyst control samples. In terms of synthetic novelty, we utilized a sustainably mild, ambient wet-synthesis method never previously applied to the fabrication ofmore » crystalline, pure ternary systems in order to fabricate ultrathin, homogeneous alloy PtRuFe NWs with a range of controlled compositions. Thus, these NWs were subsequently characterized using a suite of techniques including XRD, TEM, SAED, and EDAX in order to verify not only the incorporation of Ru and Fe into the Pt lattice but also their chemical homogeneity, morphology, as well as physical structure and integrity. Lastly, these NWs were electrochemically tested in order to deduce the appropriateness of conventional explanations such as (i) the bi-functional mechanism as well as (ii) the ligand effect to account for our MOR and FAOR reaction data. Specifically, methanol oxidation appears to be predominantly influenced by the Ru content, whereas formic acid oxidation is primarily impacted by the corresponding Fe content within the ternary metal alloy catalyst itself.« less

Tailoring magnetic behavior of CoFeMnNiX (X = Al, Cr, Ga, and Sn) high entropy alloys by metal doping

DOE PAGES

Zuo, Tingting; Gao, Michael C.; Ouyang, Lizhi; ...

2017-03-07

Magnetic materials with excellent performances are desired for functional applications. Based on the high-entropy effect, a system of CoFeMnNiX (X = Al, Cr, Ga, and Sn) magnetic alloys are designed and investigated. The dramatic change in phase structures from face-centered-cubic (FCC) to ordered body-centered-cubic (BCC) phases, caused by adding Al, Ga, and Sn in CoFeMnNiX alloys, originates from the potent short-range chemical order in the liquid state predicted by ab initio molecular dynamics (AIMD) simulations. This phase transition leads to the significant enhancement of the saturation magnetization (M s), e.g., the CoFeMnNiAl alloy has M s of 147.86 Am 2/kg.more » In conclusion, first-principles density functional theory (DFT) calculations on the electronic and magnetic structures reveal that the anti-ferromagnetism of Mn atoms in CoFeMnNi is suppressed especially in the CoFeMnNiAl HEA because Al changes the Fermi level and itinerant electron-spin coupling that lead to ferromagnetism.« less

The effect of copper doping on martensite shear stress in porous TiNi(Mo,Fe,Cu) alloys

NASA Astrophysics Data System (ADS)

Khodorenko, V. N.; Kaftaranova, M. I.; Gunther, V. E.

2015-03-01

The properties of alloys based on porous nickel-titanium (TiNi) with copper additives have been studied. It is established that the copper doping of porous TiNi(Mo,Fe,Cu) alloys fabricated by the method of self-propagating high-temperature synthesis leads to a significant decrease in the martensite shear stress (below 30 MPa). Low values of the martensite shear stress (σmin) in copper-doped TiNi-based alloys allows medical implants of complex shapes to be manufactured for various purposes, including oral surgery. The optimum concentration of copper additives (within 3-6 at %) has been determined that ensures high performance characteristics of TiNi-based porous alloys for medical implants.

Laser surface alloying of FeCoCrAlNi high-entropy alloy on 304 stainless steel to enhance corrosion and cavitation erosion resistance

NASA Astrophysics Data System (ADS)

Zhang, S.; Wu, C. L.; Zhang, C. H.; Guan, M.; Tan, J. Z.

2016-10-01

FeCoCrAlNi high-entropy alloy coating was synthesized with premixed high-purity Co, Cr, Al and Ni powders on 304 stainless steel by laser surface alloying, aiming at improving corrosion and cavitation erosion resistance. Phase constituents, microstructure and microhardness were investigated using XRD, SEM, and microhardness tester, respectively. The cavitation erosion and electrochemical corrosion behavior of FeCoCrAlNi coating in 3.5% NaCl solution were also evaluated using an ultrasonic vibrator and potentiodynamic polarization measurement. Experimental results showed that with appropriate laser processing parameters, FeCoCrAlNi coating with good metallurgical bonding to the substrate could be achieved. FeCoCrAlNi coating was composed of a single BCC solid solution. The formation of simple solid solutions in HEAs was the combined effect of mixing entropy (ΔSmix), mixing enthalpy (ΔHmix), atom-size difference (δ) and valence electron concentration (VEC), and the effect of ΔSmix was much larger than that of the other factors. The microhardness of the FeCoCrAlNi coating was ~3 times that of the 304 stainless steel. Both the corrosion and cavitation erosion resistance of the coating were improved. The cavitation erosion resistance for FeCoCrAlNi HEA coating was ~7.6 times that of 304 stainless steel. The corrosion resistance was also improved as reflected by a reduction in the current density of one order of magnitude as compared with 304 stainless steel.

Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation

NASA Astrophysics Data System (ADS)

Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

2016-08-01

Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance.

Defect energetics of concentrated solid-solution alloys from ab initio calculations: Ni0.5Co0.5, Ni0.5Fe0.5, Ni0.8Fe0.2 and Ni0.8Cr0.2.

PubMed

Zhao, Shijun; Stocks, G Malcolm; Zhang, Yanwen

2016-09-14

It has been shown that concentrated solid solution alloys possess unusual electronic, magnetic, transport, mechanical and radiation-resistant properties that are directly related to underlying chemical complexity. Because every atom experiences a different local atomic environment, the formation and migration energies of vacancies and interstitials in these alloys exhibit a distribution, rather than a single value as in a pure metal or dilute alloy. Using ab initio calculations based on density functional theory and special quasirandom structures, we have characterized the distribution of defect formation energy and migration barrier in four Ni-based solid-solution alloys: Ni0.5Co0.5, Ni0.5Fe0.5, Ni0.8Fe0.2, and Ni0.8Cr0.2. As defect formation energies in finite-size models depend sensitively on the elemental chemical potential, we have developed a computationally efficient method for determining it which takes into account the global composition and the local short-range order. In addition we have compared the results of our ab initio calculations to those obtained from available embedded atom method (EAM) potentials. Our results indicate that the defect formation and migration energies are closely related to the specific atoms in the structure, which further determines the elemental diffusion properties. Different EAM potentials yield different features of defect energetics in concentrated alloys, pointing to the need for additional potential development efforts in order to allow spatial and temporal scale-up of defect and simulations, beyond those accessible to ab initio methods.

Crystallographic, magnetic, and electronic structures of ferromagnetic shape memory alloys Ni2XGa (X=Mn,Fe,Co) from first-principles calculations

NASA Astrophysics Data System (ADS)

Bai, J.; Raulot, J. M.; Zhang, Y. D.; Esling, C.; Zhao, X.; Zuo, L.

2011-01-01

The crystallographic, magnetic and electronic structures of the ferromagnetic shape memory alloys Ni2XGa (X=Mn, Fe, and Co), are systematically investigated by means of the first-principles calculations within the framework of density functional theory using the VIENNA AB INITIO SOFTWARE PACKAGE. The lattice parameters of both austenitic and martensitic phases in Ni2MnGa have been calculated. The formation energies of the cubic phase of Ni2XGa are estimated, and show a destabilization tendency if Mn atom is substituted by Fe or Co. From Ni2MnGa to Ni2CoGa, the down spin total density of states (DOS) at Fermi level is gradually increasing, whereas that of the up spin part remains almost unchanged. This is the main origin of the difference of the magnetic moment in these alloys. The partial DOS is dominated by the Ni and Mn 3d states in the bonding region below EF. There are two bond types existing in Ni2XGa: one is between neighboring Ni atoms in Ni2MnGa; the other is between Ni and X atoms in Ni2FeGa and Ni2CoGa alloys.

Effect of Ni on Fe FeS phase relations at high pressure and high temperature

NASA Astrophysics Data System (ADS)

Zhang, Li; Fei, Yingwei

2008-04-01

A series of melting experiments in the Fe-rich portion of the Fe-Ni-S system have been conducted at 19-23 GPa and 800-1100 °C. The solubility of S in the Fe-Ni solid alloy and the eutectic melting in the Fe-Ni-S system were determined as a function of Ni content. The maximum S solubility in the Fe-Ni alloy is 2.7 wt.% at 20 GPa and the eutectic temperature. The eutectic melting temperature in the Fe-Ni(5wt.%)-S system is ~ 1000 °C lower than the melting point of pure Fe at 20 GPa. We also found that Ni can substitute Fe in the Fe 3S structure to form (Fe,Ni) 3S solid solutions up to at least a Fe/Ni atomic ratio of 0.5. Similar to melting behavior in the Fe-FeS system, the eutectic melting relations in the Fe-Ni-S system could produce inner and outer cores with the right light element balance to account for the density difference between the solid inner core and the liquid outer core.

An advanced Ni-Fe layered double hydroxide electrocatalyst for water oxidation.

PubMed

Gong, Ming; Li, Yanguang; Wang, Hailiang; Liang, Yongye; Wu, Justin Z; Zhou, Jigang; Wang, Jian; Regier, Tom; Wei, Fei; Dai, Hongjie

2013-06-12

Highly active, durable, and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions, including water-splitting and rechargeable metal-air batteries. Here, we report the synthesis of ultrathin nickel-iron layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs). Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-LDH. The crystalline NiFe-LDH phase in nanoplate form is found to be highly active for oxygen evolution reaction in alkaline solutions. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts.

Helium accumulation and bubble formation in FeCoNiCr alloy under high fluence He+ implantation

NASA Astrophysics Data System (ADS)

Chen, Da; Tong, Y.; Li, H.; Wang, J.; Zhao, Y. L.; Hu, Alice; Kai, J. J.

2018-04-01

Face-centered cubic (FCC) high-entropy alloys (HEA), as emerging alloys with equal-molar or near equal-molar constituents, show a promising radiation damage resistance under heavy ion bombardment, making them potential for structural material application in next-generation nuclear reactors, but the accumulation of light helium ions, a product of nuclear fission reaction, has not been studied. The present work experimentally studied the helium accumulation and bubble formation at implantation temperatures of 523 K, 573 K and 673 K in a homogenized FCC FeCoNiCr HEA, a HEA showing excellent radiation damage resistance under heavy ion irradiation. The size and population density of helium bubbles in FeCoNiCr samples were quantitatively analyzed through transmission electron microscopy (TEM), and the helium content existing in bubbles were estimated from a high-pressure Equation of State (EOS). We found that the helium diffusion in such condition was dominated by the self-interstitial/He replacement mechanism, and the corresponding activation energy in FeCoNiCr is comparable with the vacancy migration energy in Ni and austenitic stainless steel but only 14.3%, 31.4% and 51.4% of the accumulated helium precipitated into helium bubbles at 523 K, 573 K and 673 K, respectively, smaller than the pure Ni case. Importantly, the small bubble size suggested that FeCoNiCr HEA has a high resistance of helium bubble formation compared with Ni and steels.

Phase Evolution and Properties of Al2CrFeNiMo x High-Entropy Alloys Coatings by Laser Cladding

NASA Astrophysics Data System (ADS)

Wu, Wei; Jiang, Li; Jiang, Hui; Pan, Xuemin; Cao, Zhiqiang; Deng, Dewei; Wang, Tongmin; Li, Tingju

2015-10-01

A series of Al2CrFeNiMo x ( x = 0 to 2.0 at.%) high-entropy alloys coatings was synthesized on stainless steel by laser cladding. The effect of Mo content on the microstructures and mechanical properties of Al2CrFeNiMo x coatings was studied. The results show that the laser clad layer consists of the cladding zone, bonding zone, and heat-affected zone. The Al2CrFeNiMo x coatings are composed of two simple body-center cubic phases and the cladding zone is mainly composed of equiaxed grains. When the content of Mo reaches 2 at.%, a eutectic structure is found in the interdendritic regions. The surface microhardness of the Al2CrFeNiMo2 coating is 678 HV, which is about three times higher than that of the substrate (243 HV). Compared with stainless steel, the wear resistance of the coatings has been improved greatly. The wear mass loss of the Al2CrFeNiMo alloy is 9.8 mg, which is much less than that of the substrate (18.9 mg) and its wear scar width is the lowest among the Al2CrFeNiMo x coatings, indicating that the wear resistance of the Al2CrFeNiMo is the best.

Effect of a CoFeB layer on the anisotropic magnetoresistance of Ta/CoFeB/MgO/NiFe/MgO/CoFeB/Ta films

NASA Astrophysics Data System (ADS)

Li, Minghua; Shi, Hui; Dong, Yuegang; Ding, Lei; Han, Gang; Zhang, Yao; Liu, Ye; Yu, Guanghua

2017-10-01

The anisotropic magnetoresistance (AMR) and magnetic properties of NiFe films can be remarkably enhanced via CoFeB layer. In the case of an ultrathin NiFe film having a Ta/CoFeB/MgO/NiFe/MgO/CoFeB/Ta structure, the CoFeB/MgO layers suppressed the formation of magnetic dead layers and the interdiffusions and interface reactions between the NiFe and Ta layers. The AMR reached a maximum value of 3.56% at 450 °C. More importantly, a single NiFe (1 1 1) peak can be formed resulting in higher AMR values for films having CoFeB layer. This enhanced AMR also originated from the significant specular reflection of electrons owing to the crystalline MgO layer, together with the sharp interfaces with the NiFe layer. These factors together resulted in higher AMR and improved magnetic properties.

Local structure of high-coercivity Fe-Ni-Al alloys

NASA Astrophysics Data System (ADS)

Menushenkov, A. P.; Menushenkov, V. P.; Chernikov, R. V.; Sviridova, T. A.; Grishina, O. V.; Sidorov, V. V.

2011-04-01

Results of hard magnetic Fe-Ni-Al alloys after various thermal processing local structure researches by method of EXAFS-spectroscopy with use of synchrotron radiation at temperature 77 K are presented. It is established, that during cooling a firm solution with critical speed reorganization of a local environment of nickel relative to quickly tempered sample owing to stratification of a firm solution is observed. The subsequent aging at 780°C practically restores local structure, characteristic for quickly tempered sample, keeping thus rather high coercitive force.

Chemical complexity induced local structural distortion in NiCoFeMnCr high-entropy alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fuxiang; Tong, Yang; Jin, Ke

In order to study chemical complexity-induced lattice distortion in high-entropy alloys, the static Debye–Waller (D-W) factor of NiCoFeMnCr solid solution alloy is measured with low temperature neutron diffraction, ambient X-ray diffraction, and total scattering methods. Here, the static atomic displacement parameter of the multi-element component alloy at 0 K is 0.035–0.041 Å, which is obvious larger than that of element Ni (~0 Å). The atomic pair distance between individual atoms in the alloy investigated with extended X-ray absorption fine structure (EXAFS) measurements indicates that Mn has a slightly larger bond distance (~0.4%) with neighbor atoms than that of others.

Chemical complexity induced local structural distortion in NiCoFeMnCr high-entropy alloy

DOE PAGES

Zhang, Fuxiang; Tong, Yang; Jin, Ke; ...

2018-06-16

In order to study chemical complexity-induced lattice distortion in high-entropy alloys, the static Debye–Waller (D-W) factor of NiCoFeMnCr solid solution alloy is measured with low temperature neutron diffraction, ambient X-ray diffraction, and total scattering methods. Here, the static atomic displacement parameter of the multi-element component alloy at 0 K is 0.035–0.041 Å, which is obvious larger than that of element Ni (~0 Å). The atomic pair distance between individual atoms in the alloy investigated with extended X-ray absorption fine structure (EXAFS) measurements indicates that Mn has a slightly larger bond distance (~0.4%) with neighbor atoms than that of others.

Effect of 1.0% Ni on high-temperature impression creep and hardness of recycled aluminium alloy with high Fe content

NASA Astrophysics Data System (ADS)

Faisal, M.; Mazni, Noor; Prasada Rao, A. K.

2018-03-01

Reported work focusses on the effect of 1.0% Ni addition on the microstructure, high- temperature impression creep and thereby the hardness of recycled Al-alloy containing >2wt% Fe, obtained from automotive scrap. Present studies have shown that the addition of 1.0% Ni have supress the formation of α-phase (Al5FeSi) by supressing the peritectic transformation of β-phase (Al8Fe2Si). Such suppression is found to improve the hardness and high-temperature impression creep of the recycled aluminium alloy.

Microstructural evolution of single Ni 2TiAl or hierarchical NiAl/Ni 2 TiAl precipitates in Fe-Ni-Al-Cr-Ti ferritic alloys during thermal treatment for elevated-temperature applications

DOE PAGES

Song, Gian; Sun, Zhiqian; Poplawsky, Jonathan D.; ...

2017-01-07

Precipitate features, such as the size, morphology, and distribution, are important parameters determining the mechanical properties of semi- or fully-coherent precipitatehardened alloys at elevated temperatures. In this study, the microstructural formation and evolution of recently-developed Fe-Ni-Al-Cr-Ti alloys with superior creep resistance have been systematically investigated using transmission-electron microscopy (TEM), scanning-electron microscopy (SEM), and atom-probe tomography (APT). These alloys were designed by adding 2 or 4 weight percent (wt. %) Ti into a NiAl-hardened ferritic alloy with a nominal composition of Fe-6.5Al-10Cr-10Ni-3.4Mo-0.25Zr-0.005B in wt. %. These alloys were, then, subjected to a homogenization treatment at 1,473 K for 0.5 hour, followedmore » by aging treatments at 973 K for 1 ~ 500 hours. In the homogenization-treated case, both alloys contain a primary L21-type Ni 2TiAl precipitate, but with the distinct size and morphology of the precipitates and precipitate/matrix interface structures. In the subsequent aging treatments, the 2 wt. % Ti alloy establishes a hierarchical-precipitate structure consisting of a fine network of a B2-type NiAl phase within the parent L2 1-type Ni2TiAl precipitate, while the 4 wt. % Ti alloy retains the single Ni 2TiAl precipitate. It was found that the hierarchical structure is more effective in remaining the coherent interface during the growth/coarsening of the precipitate. The formation of the different types of the precipitates, and their effects on the microstructural evolution are discussed, and the driving forces for these features are identified from the competition between the interface energy and elastic interactions due to the lattice misfit and misfit dislocations.« less

Microstructural evolution of single Ni 2TiAl or hierarchical NiAl/Ni 2 TiAl precipitates in Fe-Ni-Al-Cr-Ti ferritic alloys during thermal treatment for elevated-temperature applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Gian; Sun, Zhiqian; Poplawsky, Jonathan D.

Precipitate features, such as the size, morphology, and distribution, are important parameters determining the mechanical properties of semi- or fully-coherent precipitatehardened alloys at elevated temperatures. In this study, the microstructural formation and evolution of recently-developed Fe-Ni-Al-Cr-Ti alloys with superior creep resistance have been systematically investigated using transmission-electron microscopy (TEM), scanning-electron microscopy (SEM), and atom-probe tomography (APT). These alloys were designed by adding 2 or 4 weight percent (wt. %) Ti into a NiAl-hardened ferritic alloy with a nominal composition of Fe-6.5Al-10Cr-10Ni-3.4Mo-0.25Zr-0.005B in wt. %. These alloys were, then, subjected to a homogenization treatment at 1,473 K for 0.5 hour, followedmore » by aging treatments at 973 K for 1 ~ 500 hours. In the homogenization-treated case, both alloys contain a primary L21-type Ni 2TiAl precipitate, but with the distinct size and morphology of the precipitates and precipitate/matrix interface structures. In the subsequent aging treatments, the 2 wt. % Ti alloy establishes a hierarchical-precipitate structure consisting of a fine network of a B2-type NiAl phase within the parent L2 1-type Ni2TiAl precipitate, while the 4 wt. % Ti alloy retains the single Ni 2TiAl precipitate. It was found that the hierarchical structure is more effective in remaining the coherent interface during the growth/coarsening of the precipitate. The formation of the different types of the precipitates, and their effects on the microstructural evolution are discussed, and the driving forces for these features are identified from the competition between the interface energy and elastic interactions due to the lattice misfit and misfit dislocations.« less

Hydrogen-Resistant Fe/Ni/Cr-Base Superalloy

NASA Technical Reports Server (NTRS)

Bhat, Biliyar N.; Chen, Po-Shou; Panda, Binayak

1994-01-01

Strong Fe/Ni/Cr-base hydrogen- and corrosion-resistant alloy developed. Superalloy exhibits high strength and exceptional resistance to embrittlement by hydrogen. Contains two-phase microstructure consisting of conductivity precipitated phase in conductivity matrix phase. Produced in wrought, weldable form and as castings, alloy maintains high ductility and strength in air and hydrogen. Strength exceeds previously known Fe/Cr/Ni hydrogen-, oxidation-, and corrosion-resistant alloys. Provides higher strength-to-weight ratios for lower weight in applications as storage vessels and pipes that must contain hydrogen.

Interplay of electronic, structural and magnetic properties as the driving feature of high-entropy CoCrFeNiPd alloys

NASA Astrophysics Data System (ADS)

Calvo-Dahlborg, M.; Cornide, J.; Tobola, J.; Nguyen-Manh, D.; Wróbel, J. S.; Juraszek, J.; Jouen, S.; Dahlborg, U.

2017-05-01

The structural and magnetic properties of CoCrFe y Ni and CoCrFeNi-Pd x alloys earlier investigated experimentally by x-ray and neutron diffraction techniques and magnetometry have been theoretically reproduced using two complementary approaches for electronic structure calculations, i.e. the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA) and implemented in the ab initio framework of density functional theory and the Vienna ab initio simulation package (VASP) for supercell models of high-entropy alloy (HEA) structures. The comparison between experimental results and calculations of the lattice constants by both calculation methods indicate that the structure of CoCrFe y Ni is well described by ordered fcc configurations. The values of local magnetic moments on Fe, Co, Cr, and Ni atoms depend not only on the Pd concentration but on chemical disordering. In the case of the CoCrFeNi-Pd x alloys, the KKR-CPA and the VASP calculations of disordered configurations reproduce the experimental values at 5 K up to equimolar composition and at 300 K above. The experimental values above the equimolar composition at 5 K are not satisfactorily reproduced by any of the calculations. The divergence between the experimental and calculated values is related to the variation of the ferromagnetic to paramagnetic transition temperature as a function of palladium content and to the existence of several phases, FeCoCr-rich above room temperature and FeCrPd-rich below, observed by diffraction and detected by microscopy and atom probe investigations. VASP calculations of a FeCrPd-rich phase effectively reproduced both the lattice constant and magnetization of the alloy above equimolar composition. An important conclusion of this work is that the combined analysis of the electronic, structural, and magnetic properties plays an important role in understanding the complexity of magnetic HEAs.

Radiation damage buildup and dislocation evolution in Ni and equiatomic multicomponent Ni-based alloys

NASA Astrophysics Data System (ADS)

Levo, E.; Granberg, F.; Fridlund, C.; Nordlund, K.; Djurabekova, F.

2017-07-01

Single-phase multicomponent alloys of equal atomic concentrations ("equiatomic") have proven to exhibit promising mechanical and corrosion resistance properties, that are sought after in materials intended for use in hazardous environments like next-generation nuclear reactors. In this article, we investigate the damage production and dislocation mobility by simulating irradiation of elemental Ni and the alloys NiCo, NiCoCr, NiCoFe and NiFe, to assess the effect of elemental composition. We compare the defect production and the evolution of dislocation networks in the simulation cells of two different sizes, for all five studied materials. We find that the trends in defect evolution are in good agreement between the different cell sizes. The damage is generally reduced with increased alloy complexity, and the dislocation evolution is specific to each material, depending on its complexity. We show that increasing complexity of the alloys does not always lead to decreased susceptibility to damage accumulation under irradiation. We show that, for instance, the NiCo alloy behaves very similarly to Ni, while presence of Fe or Cr in the alloy even as a third component reduces the saturated level of damage substantially. Moreover, we linked the defect evolution with the dislocation transformations in the alloys. Sudden drops in defect number and large defect fluctuations from the continuous irradiation can be explained from the dislocation activity.

Thermophysical properties of Ni-containing single-phase concentrated solid solution alloys

DOE PAGES

Jin, Ke; Mu, Sai; An, Ke; ...

2016-12-27

For this research temperature dependent thermophysical properties, including specific heat capacity, lattice thermal expansion, thermal diffusivity and conductivity, have been systematically studied in Ni and eight Ni-containing single-phase face-centered-cubic concentrated solid solution alloys, at elevated temperatures up to 1273 K. The alloys have similar specific heat values of 0.4–0.5 J·g -1·K -1 at room temperature, but their temperature dependence varies greatly due to Curie and K-state transitions. The lattice, electronic, and magnetic contributions to the specific heat have been separated based on first-principles methods in NiCo, NiFe, Ni-20Cr and NiCoFeCr. The alloys have similar thermal expansion behavior, with the exceptionmore » that NiFe and NiCoFe have much lower thermal expansion coefficient in their ferromagnetic state due to magnetostriction effects. Calculations based on the quasi-harmonic approximation accurately predict the temperature dependent lattice parameter of NiCo and NiFe with < 0.2% error, but underestimated that of Ni-20Cr by 1%, compared to the values determined from neutron diffraction. In addition, all the alloys containing Cr have very similar thermal conductivity, which is much lower than that of Ni and the alloys without Cr, due to the large magnetic disorder.« less

Defect energetics of concentrated solid-solution alloys from ab initio calculations: Ni 0.5Co 0.5, Ni 0.5Fe 0.5, Ni 0.8Fe 0.2 and Ni 0.8Cr 0.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Shijun; Stocks, George Malcolm; Zhang, Yanwen

2016-08-03

It has been shown that concentrated solid solution alloys possess unusual electronic, magnetic, transport, mechanical and radiation-resistant properties that are directly related to underlying chemical complexity. Because every atom experiences a different local atomic environment, the formation and migration energies of vacancies and interstitials in these alloys exhibit a distribution, rather than a single value as in a pure metal or dilute alloy. In this study, using ab initio calculations based on density functional theory and special quasirandom structure, we have characterized the distribution of defect formation energy and migration barrier in four Ni-based solid-solution alloys: Ni 0.5Co 0.5, Nimore » 0.5Fe 0.5, Ni 0.8Fe 0.2 and Ni 0.8Cr 0.2. As defect formation energies in finite-size models depend sensitively on the elemental chemical potential, we have developed a computationally efficient method for determining it which takes into account the global composition and the local short-range order. In addition we have compared the results of our ab initio calculations to those obtained from available embedded atom method (EAM) potentials. Our results indicate that the defect formation and migration energies are closely related to the specific atomic size in the structure, which further determines the elemental diffusion properties. In conclusion, different EAM potentials yield different features of defect energetics in concentrated alloys, pointing to the need for additional potential development efforts in order to allow spatial and temporal scale-up of defect and simulations, beyond those accessible to ab initio methods.« less

Structure and properties of electrodeposited nanocrystalline Ni and Ni-Fe alloy continuous foils

NASA Astrophysics Data System (ADS)

Giallonardo, Jason Derek

This research work presents the first comprehensive study on nanocrystalline materials produced in bulk quantities using a novel continuous electrodeposition process. A series of nanocrystalline Ni and Ni-Fe alloy continuous foils were produced and an intensive investigation into their structure and various properties was carried out. High-resolution transmission electron microscopy (HR-TEM) revealed the presence of local strain at high and low angle, and twin boundaries. The cause for these local strains was explained based on the interpretation of non-equilibrium grain boundary structures that result when conditions of compatibility are not satisfied. HR-TEM also revealed the presence of twin faults of the growth type, or "growth faults", which increased in density with the addition of Fe. This observation was found to be consistent with a corresponding increase in the growth fault probabilities determined quantitatively using X-ray diffraction (XRD) pattern analysis. Hardness and Young's modulus were measured by nanoindentation. Hardness followed the regular Hall-Petch behaviour down to a grain size of 20 nm after which an inverse trend was observed. Young's modulus was slightly reduced at grain sizes less than 20 nm and found to be affected by texture. Microstrain based on XRD line broadening was measured for these materials and found to increase primarily with a decrease in grain size or an increase in intercrystal defect density (i.e., grain boundaries and triple junctions). This microstrain is associated with the local strains observed at grain boundaries in the HR-TEM image analysis. A contribution to microstrain from the presence of growth faults in the nanocrystalline Ni-Fe alloys was also noted. The macrostresses for these materials were determined from strain measurements using a two-dimensional XRD technique. At grain sizes less than 20 nm, there was a sharp increase in compressive macrostresses which was also owed to the corresponding increase in

Improved magnetic and electrical properties of Cu doped Fe-Ni invar alloys synthesized by chemical reduction technique

NASA Astrophysics Data System (ADS)

Ahmad, Sajjad; Ziya, Amer Bashir; Ashiq, Muhammad Naeem; Ibrahim, Ather; Atiq, Shabbar; Ahmad, Naseeb; Shakeel, Muhammad; Khan, Muhammad Azhar

2016-12-01

Fe-Ni-Cu invar alloys of various compositions (Fe65Ni35-xCux, x=0, 0.2, 0.6, 1, 1.4 and 1.8) were synthesized via chemical reduction route. These alloys were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM) techniques. The XRD analysis revealed the formation of face centered cubic (fcc) structure. The lattice parameter and the crystallite size of the investigated alloys were calculated and the line broadening indicated the nano-crystallites size of alloy powder. The particle size was estimated from SEM and it decreases by the incorporation of Cu and found to be in the range of 24-40 nm. The addition of Cu in these alloys appreciably enhances the saturation magnetization and it increases from 99 to 123 emu/g. Electrical conductivity has been improved with Cu addition. The thermal conductivity was calculated using the Wiedemann-Franz law.

Magnetic Behavior of Ni-Fe Core-Shell and Alloy Nanowires

NASA Astrophysics Data System (ADS)

Tripathy, Jagnyaseni; Vargas, Jose; Spinu, Leonard; Wiley, John

2013-03-01

Template assisted synthesis was used to fabricate a series of Ni-Fe core-shell and alloy nanowires. By controlling reaction conditions as well as pore structure, both systems could be targeted and magnetic properties followed as a function of architectures. In the core-shell structure coercivity increases with decrease in shell thickness while for the alloys, coercivity squareness improve with increase pore diameter. Details on the systematic studies of these materials will be presented in terms of hysteretic measurements, including first order reversal curves (FORC), and FMR data. Magnetic variation as a function of structure and nanowire aspect ratios will be presented and the origins of these behaviors discussed. Advanced Material Research Institute

High-pressure and high-temperature phase diagram for Fe0.9Ni0.1-H alloy

NASA Astrophysics Data System (ADS)

Shibazaki, Yuki; Terasaki, Hidenori; Ohtani, Eiji; Tateyama, Ryuji; Nishida, Keisuke; Funakoshi, Ken-ichi; Higo, Yuji

2014-03-01

Planetary cores are considered to consist of an iron-nickel (Fe-Ni) alloy and light elements and hydrogen is one of plausible light elements in the core. Here we have performed in situ X-ray diffraction experiments on an Fe0.9Ni0.1-H system up to 15.1 GPa and 1673 K, and investigated the effect of Ni on phase relations of FeHx under high pressure and high temperature. The experimental system in the present work was oversaturated with hydrogen. We found a face-center-cubic (fcc) phase (with hydrogen concentration up to x∼1) and a body-center-cubic (bcc) phase (x < 0.1) as stable phases. The partial melting was observed below 6 GPa. We could not observe a double-hexagonal-close-packed (dhcp) phase because of limitations in pressure and temperature conditions. The stability field of each phase of Fe0.9Ni0.1Hx was almost same as that of FeHx. The solidus of Fe0.9Ni0.1Hx was 500-700 K lower than the melting curve of Fe and its liquidus was 400-600 K lower than that of Fe in the pressure range of this study. Both the solidus and liquidus of Fe0.9Ni0.1Hx were depressed at around 3.5 GPa, as was the solidus of FeHx. The hydrogen contents in fcc-Fe0.9Ni0.1Hx just below solidus were slightly lower than those of fcc-FeHx, which suggests that nickel is likely to prevent dissolution of hydrogen into iron. Due to the lower hydrogen solubilities in Fe0.9Ni0.1 compared to Fe, the solidus of Fe0.9Ni0.1Hx is about 100-150 K higher than that of FeHx.

Effect of Heat Treatment on Morphology of Fe-Rich Intermetallics in Hypereutectic Al-Si-Cu-Ni Alloy with 1.26 pct Fe

NASA Astrophysics Data System (ADS)

Sha, Meng; Wu, Shusen; Wan, Li; Lü, Shulin

2013-12-01

Cobalt is generally considered as the element that can neutralize the negative effects of iron in Al alloys, such as inducing fracture and failure for stress concentration. Nevertheless, Fe-rich intermetallics would be inclined to form coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles when the content of Fe was high, which could also cause inferior mechanical properties. The dissolution and transformation of δ-Al4(Fe, Co, Ni)Si2 phase in solution heat-treated samples of Al-20Si-1.85Cu-1.05Ni-1.26Fe-1.35Co alloy were studied using optical microscopy, image analysis, and scanning electron microscopy. The effects of solution heat treatment time ranging from 0 to 9 hours at 783.15 K (510 °C) on mechanical properties were also investigated. The coarse plate-like δ-Al4(Fe, Co, Ni)Si2 particles varied slowly through concurrent dissolution along widths and at the plate tips as solution treatment time increased, which could be explained from diffusion-induced grain boundary migration. Solution heat treatment also has an important influence on mechanical properties. The maximum ultimate tensile strength and yield strength after T6 treatment were 258 and 132 MPa, respectively, while the maximum hardness was 131 HB. Compared with those of the samples in the as-cast state, they increased by 53, 42, and 28 pct, respectively. Moreover, δ-Al4(Fe, Co, Ni)Si2 phase, which appears as a coarse plate-like particle in two dimensions, is actually a cuboid in three dimensions. The length of this cuboid is close to the width, while the height is much smaller.

Ion irradiation induced defect evolution in Ni and Ni-based FCC equiatomic binary alloys

DOE PAGES

Jin, Ke; Zhang, Yanwen; Bei, Hongbin

2015-09-09

In order to explore the chemical effects on radiation response of alloys with multi-principal elements, defect evolution under Au ion irradiation was investigated in the elemental Ni, equiatomic NiCo and NiFe alloys. Single crystals were successfully grown in an optical floating zone furnace and their (100) surfaces were irradiated with 3 MeV Au ions at fluences ranging from 1 × 10 13 to 5 × 10 15 ions cm –2 at room temperature. The irradiation-induced defect evolution was analyzed by using ion channeling technique. Experiment shows that NiFe is more irradiation-resistant than NiCo and pure Ni at low fluences. Withmore » continuously increasing the ion fluences, damage level is eventually saturated for all materials but at different dose levels. The saturation level in pure Ni appears at relatively lower irradiation fluence than the alloys, suggesting that damage accumulation slows down in the alloys. Here, under high-fluence irradiations, pure Ni has wider damage ranges than the alloys, indicating that defects in pure Ni have high mobility.« less

Formation and investigation of ultrathin layers of Co2FeSi ferromagnetic alloy synthesized on silicon covered with a CaF2 barrier layer

NASA Astrophysics Data System (ADS)

Grebenyuk, G. S.; Gomoyunova, M. V.; Pronin, I. I.; Vyalikh, D. V.; Molodtsov, S. L.

2016-03-01

Ultrathin (∼2 nm) films of Co2FeSi ferromagnetic alloy were formed on silicon by solid-phase epitaxy and studied in situ. Experiments were carried out in an ultrahigh vacuum (UHV) using substrates of Si(1 1 1) single crystals covered with a 5 nm thick CaF2 barrier layer. The elemental and phase composition as well as the magnetic properties of the synthesized films were analyzed by photoelectron spectroscopy using synchrotron radiation and by magnetic linear dichroism in photoemission of Fe 3p and Co 3p electrons. The study shows that the synthesis of the Co2FeSi ferromagnetic alloy occurs in the temperature range of 200-400 °C. At higher temperatures, the films become island-like and lose their ferromagnetic properties, as the CaF2 barrier layer is unable to prevent a mass transfer between the film and the Si substrate, which violates the stoichiometry of the alloy.

The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al based intermetallic phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samolyuk, G. D.; Stocks, G. M.; Újfalussy, B.

Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co, and Ti within the AlNi-based matrix phase. In this paper, we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which correspond to experimental situation, Ti and Fe are found to occupy the α sites, while Co and Ni prefer the γ sites of the DO{sub 3} lattice. An important finding is that the magnetic moments of transition metals in Fe{sub 3}Al and Co{sub 3}Al are ordered ferromagnetically, whereas the Ni{sub 3}Al were found to be nonmagnetic unless the Fe or Co is added as a ternary element.« less

Phase Evolution and Mechanical Properties of AlCoCrFeNiSi x High-Entropy Alloys Synthesized by Mechanical Alloying and Spark Plasma Sintering

NASA Astrophysics Data System (ADS)

Kumar, Anil; Swarnakar, Akhilesh Kumar; Chopkar, Manoj

2018-05-01

In the current investigation, AlCoCrFeNiSi x (x = 0, 0.3, 0.6 and 0.9 in atomic ratio) high-entropy alloy systems are prepared by mechanical alloying and subsequently consolidated by spark plasma sintering. The microstructural and mechanical properties were analyzed to understand the effect of Si addition in AlCoCrFeNi alloy. The x-ray diffraction analysis reveals the supersaturated solid solution of the body-centered cubic structure after 20 h of ball milling. However, the consolidation promotes the transformation of body-centered phases partially into the face-centered cubic structure and sigma phases. A recently proposed geometric model based on the atomic stress theory has been extended for the first time to classify single phase and multi-phases on the high-entropy alloys prepared by mechanical alloying and spark plasma sintering process. Improved microhardness and better wear resistance were achieved as the Si content increased from 0 to 0.9 in the present high-entropy alloy.

Effect of Alloying Additions on Oxidation Behaviors of Ni-Fe Based Superalloy for Ultra-Supercritical Boiler Applications

NASA Astrophysics Data System (ADS)

Lu, Jintao; Yang, Zhen; Zhao, Xinbao; Yan, Jingbo; Gu, Y.

A new kind of Ni-Fe-based superalloy is designed recently for 750 °C-class A-USC boiler tube. The oxidation behavior of the designed alloys with various combinations of anti-oxidation additions, Cr, Al and Si, was investigated at 750 °C and 850 °C, respectively. The results indicated that the oxidation rate of tested alloys decreased with the increase of the sum of additions. Cr addition may drop the relative constant of parabolic rate greatly when temperature is raised. But the oxide scale, mainly consisted of NiCr spinel at 750 °C and NiCrMn spinel at 850 °C, was similar while the Cr content is in a range of 20-25 wt.% at tested temperatures. Al addition, however, showed the best effective to reduce the oxidation rates. Internal Al-rich oxide was observed at the scale/metal interface for alloys added with high content of Al and was increased with Al content increase. Very tiny difference between the oxide scales of the Si-added alloys was identified when Si content varies among 0.02-0.05 wt.%. Basing on these results, this presentation discussed the optimum combination of anti-oxidation additions as well as oxidation mechanisms in the designed Ni-Fe-base superalloy.

Mechanical Properties of High Entropy Alloy Al0.1CoCrFeNi for Peripheral Vascular Stent Application.

PubMed

Alagarsamy, Karthik; Fortier, Aleksandra; Komarasamy, Mageshwari; Kumar, Nilesh; Mohammad, Atif; Banerjee, Subhash; Han, Hai-Chao; Mishra, Rajiv S

2016-12-01

High entropy alloys (HEAs) are new class of metallic materials with five or more principal alloying elements. Due to this distinct concept of alloying, the HEAs exhibit unique properties compared to conventional alloys. The outstanding properties of HEAs include increased strength, superior wear resistance, high temperature stability, increased fatigue properties, good corrosion, and oxidation resistance. Such characteristics of HEAs have generated significant interest among the scientific community. However, their applications are yet to be explored. This paper discusses the mechanical behavior and microstructure of Al 0.1 CoCrFeNi HEA subjected to thermo-mechanical processing, and its potential application in peripheral vascular stent implants that are prone to high failure rates. Results show that Al 0.1 CoCrFeNi alloy possesses characteristics that compare well against currently used stent materials and it can potentially find use in peripheral vascular stent implants and extend their life-cycle.

Evolution of irradiation-induced strain in an equiatomic NiFe alloy

DOE PAGES

Ullah, Mohammad W.; Zhang, Yanwen; Sellami, Neila; ...

2017-07-10

Here, we investigate the formation and accumulation of irradiation-induced atomic strain in an equiatomic NiFe concentrated solid-solution alloy using both atomistic simulations and x-ray diffraction (XRD) analysis of irradiated samples. Experimentally, the irradiations are performed using 1.5 MeV Ni ions to fluences ranging from 1 × 10 13 to 1 × 10 14 cm -2. The irradiation simulations are carried out by overlapping 5 keV Ni recoils cascades up to a total of 300 recoils. An increase of volumetric strain is observed at low dose, which is associated with production of point defects and small clusters. A relaxation of strainmore » occurs at higher doses, when large defect clusters, like dislocation loops, dominate.« less

Fabrication and Properties of Novel NiWFeB Amorphous Alloys

NASA Astrophysics Data System (ADS)

Zhang, Jiajia; Liu, Wensheng; Ma, Yunzhu; Ye, Xiaoshan; Wu, Yayu

2017-09-01

In this work, we reported the successful synthesis of four quaternary NiWFeB amorphous alloys (Ni53.9W4.3Fe24.2B17.6, Ni49.7W9.7Fe22.3B18.3, Ni46.2W14.1Fe20.8B18.9 and Ni42.2W19.2Fe18.9B19.7 in at.%) via melt spinning method. The synthesized amorphous alloys are characterized by x-ray diffraction, transmission electron microscopy, differential scanning calorimeter, scanning electron microscopy and Vickers indenters. The results showed that the crystallization temperatures T x1 of four amorphous alloys with increased W contents, derived from the exothermic peaks in DSC, were 705, 715, 851, and 965 K, respectively. The Vickers hardness ( H v) of the corresponding four amorphous alloys at room temperature was 8.5, 9.8, 10.3, and 11.4 GPa, respectively. The much finer shear bands in the deformation region underneath the Vickers indenter were observed as the tungsten content increases. All the results showed a tendency that the higher the tungsten content, the greater the thermal stability and hardness. The results indicated the NiWFeB amorphous alloys could be easier fabricated by continuing to increase the tungsten content, and those NiWFeB amorphous alloys would have a promising application in nuclear energies and military defenses.

Investigation of FeNiCrWMn - a new high entropy alloy

NASA Astrophysics Data System (ADS)

Buluc, G.; Florea, I.; Bălţătescu, O.; Florea, R. M.; Carcea, I.

2015-11-01

The term of high entropy alloys started from the analysis of multicomponent alloys, which were produced at an experimental level since 1995 by developing a new concept related to the development of metallic materials. Recent developments in the field of high-entropy alloys have revealed that they have versatile properties like: ductility, toughness, hardness and corrosion resistance [1]. Up until now, it has been demonstrated that the explored this alloys are feasible to be synthesized, processed and analyzed contrary to the misunderstanding based on traditional experiences. Moreover, there are many opportunities in this field for academic studies and industrial applications [1, 2]. As the combinations of composition and process for producing high entropy alloys are numerous and each high entropy alloy has its own microstructure and properties to be identified and understood, the research work is truly limitless. The novelty of these alloys consists of chemical composition. These alloys have been named high entropy alloys due to the atomic scale mixing entropies higher than traditional alloys. In this paper, I will present the microscopy and the mechanical properties of high entropy alloy FeNiCrWMn.

Alloying effects of Ni, Si, and S on the phase diagram and sound velocities of Fe under high pressures and high temperatures

NASA Astrophysics Data System (ADS)

Lin, J.; Fei, Y.; Sturhahn, W.; Zhao, J.; Mao, H.; Hemley, R.

2004-05-01

Iron-nickel is the most abundant constituent of the Earth's core. The amount of Ni in the core is about 5.5 wt%. Geophysical and cosmochemical studies suggest that the Earth's outer core also contains approximately 10% of light element(s) and a certain amount of light element(s) may be present in the inner core. Si and S are believed to be alloying light elements in the iron-rich planetary cores such as the Earth and Mars. Therefore, understanding the alloying effects of Ni, Si, and S on the phase diagram and physical properties of Fe under core conditions is crucial for geophysical and geochemical models of planetary interiors. The addition of Ni and Si does not appreciably change the compressibility of hcp-Fe under high pressures. Studies of the phase relations of Fe and Fe-Ni alloys indicate that Fe with up to 10 wt% Ni is likely to be in the hcp structure under inner core conditions. On the other hand, adding Si into Fe strongly stabilizes the bcc structure to much higher pressures and temperatures (Lin et al., 2002). We have also studied the sound velocities and magnetic properties of Fe0.92Ni0.08, Fe0.85Si0.15, and Fe3S alloys with nuclear resonant inelastic x-ray scattering and nuclear forward scattering up to 106 GPa, 70 GPa, and 57 GPa, respectively. The sound velocities of the alloys are obtained from the measured partial phonon density of states for 57Fe incorporated in the alloys. Addition of Ni slightly decreases the VP and VS of Fe under high pressures (Lin et al., 2003). Si or S alloyed with Fe increases the VP and VS under high pressures, which provides a better match to seismological data of the Earth's core. We note that the increase in the VP and VS of Fe0.85Si0.15 and Fe3S is mainly contributed from the density decrease of adding Si and S in iron. Time spectra of the nuclear forward scattering reveal that the most iron rich sulfide, Fe3S, undergoes a magnetic to non-magnetic transition at approximately 18 GPa from a low-pressure magnetically

10,000-Hour Cyclic Oxidation Behavior at 982 C (1800 F) of 68 High-Temperature Co-, Fe-, and Ni-Base Alloys

NASA Technical Reports Server (NTRS)

Barrett, Charles A.

1997-01-01

Sixty-eight high temperature Co-, Fe-, and Ni-base alloys were tested for 10-one thousand hour cycles in static air at 982 C (1800 F). The oxidation behavior of the test samples was evaluated by specific weight change/time data, x-ray diffraction of the post-test samples, and their final appearance. The gravimetric and appearance data were combined into a single modified oxidation parameter, KB4 to rank the cyclic oxidation resistance from excellent to catastrophic. The alloys showing the 'best' resistance with no significant oxidation attack were the alumina/aluminate spinel forming Ni-base turbine alloys: U-700, NASA-VIA and B-1900; the Fe-base ferritic alloys with Al: TRW-Valve, HOS-875, NASA-18T, Thermenol and 18SR; and the Ni-base superalloy IN-702.

Phase evolution, mechanical and corrosion behavior of Fe(100-x) Ni(x) alloys synthesized by powder metallurgy

NASA Astrophysics Data System (ADS)

Singh, Neera; Parkash, Om; Kumar, Devendra

2018-03-01

In the present investigation, Fe(100-x) Ni(x) alloys (x = 10, 20, 30, 40 and 50 wt%) were synthesized through the evolution of γ-taenite and α-kamacite phases by powder metallurgy route using commercially available Fe and Ni powders. Mechanically mixed powders of Fe and Ni were compacted at room temperature and sintered at three different temperatures 1000, 1200 and 1250 °C for 1 h. Both Ni concentration and sintering temperature have shown a strong impact on the phase formation, tribological and electrochemical behavior. Micro structural study has shown the formation of taenite (γ-Fe,Ni) and kamacite (α-Fe,Ni) phases in the sintered specimens. An increase in Ni fraction resulted in formation of more taenite which reduces hardness and wear resistance of specimens. Increasing the sintering temperature decreased the defect concentration with enhanced taenite formation, aiding to higher densification. Taenite formed completely in Fe50Ni50 after sintering at 1250 °C. Tribological test revealed the maximum wear resistance for Fe70Ni30 specimen due to the presence of both kamacite and taenite in significant proportions. The formation of taenite as well as the decrease in defect concentration improves the corrosion resistance of the specimens significantly in 1M HCl solution. A maximum corrosion protection efficiency of around ∼87% was achieved in acidic medium for Fe50Ni50, sintered at 1250 °C.

Co-reduction of Copper Smelting Slag and Nickel Laterite to Prepare Fe-Ni-Cu Alloy for Weathering Steel

NASA Astrophysics Data System (ADS)

Guo, Zhengqi; Pan, Jian; Zhu, Deqing; Zhang, Feng

2018-02-01

In this study, a new technique was proposed for the economical and environmentally friendly recovery of valuable metals from copper smelting slag while simultaneously upgrading nickel laterite through a co-reduction followed by wet magnetic separation process. Copper slag with a high FeO content can decrease the liquidus temperature of the SiO2-Al2O3-CaO-MgO system and facilitate formation of liquid phase in a co-reduction process with nickel laterite, which is beneficial for metallic particle growth. As a result, the recovery of Ni, Cu, and Fe was notably increased. A crude Fe-Ni-Cu alloy with 2.5% Ni, 1.1% Cu, and 87.9% Fe was produced, which can replace part of scrap steel, electrolytic copper, and nickel as the burden in the production of weathering steel by an electric arc furnace. The study further found that an appropriate proportion of copper slag and nickel laterite in the mixture is essential to enhance the reduction, acquire appropriate amounts of the liquid phase, and improve the growth of the metallic alloy grains. As a result, the liberation of alloy particles in the grinding process was effectively promoted and the metal recovery was increased significantly in the subsequent magnetic separation process.

Evaluation of the Mechanical Properties of Electroslag Refined Fe-12Ni Alloys

NASA Technical Reports Server (NTRS)

Bhat, G. K.

1978-01-01

Three Fe-12Ni alloys, individually alloyed with small amounts of V, Ti, and Al, were manufactured through different melting techniques, with special emphasis on electroslag remelting, in order to achieve different levels of metal purity and associated costs. The relative effectiveness of these melting techniques was evaluated from tensile and slow bend fracture toughness behavior at 25 C and -196 C after tempering the test specimens at various temperatures. The best melting procedure was vacuum induction melting (VIM) with or without electroslag remelting (ESR). VIM+ESR is the recommended procedure since ESR provides increased yield of plate product, a reduction of overall manufacturing costs and, depending on the alloy composition, improved tensile and fracture toughness properties.

Irradiation-induced damage evolution in concentrated Ni-based alloys

DOE PAGES

Velisa, Gihan; Ullah, Mohammad Wali; Xue, Haizhou; ...

2017-06-06

Understanding the effects of chemical complexity from the number, type and concentration of alloying elements in single-phase concentred solid-solution alloys (SP-CSAs) on defect dynamics and microstructure evolution is pivotal for developing next-generation radiation-tolerant structural alloys. A specially chosen set of SP-CSAs with different chemical complexity (Ni 80Fe 20, Ni 80Cr 20 and Ni 40Fe 40Cr 20) are investigated using 1.5 MeV Mn ions over a wide fluence range, from 2 × 10 13 to 1 × 10 16 ions cm –2 at room temperature. Based on an integrated study of Rutherford backscattering spectroscopy in channeling geometry and molecular dynamics simulations,more » the results demonstrate that Ni 40Fe 40Cr 20 is more radiation tolerant than Ni 80Fe 20, Ni 80Cr 20 and elemental Ni in the low fluence regime. While chemical complexity of this set of SP-CSAs is clearly demonstrated to affect defect evolution through suppressed defect production and enhanced recombination at early stages, the effect of the mixed ferro- and anti-ferromagnetic interactions is not the only controlling factor responsible for the improved radiation performance. As a result, the observed strong alloying effect on defect evolution is attributed to the altered defect migration mobilities of defect clusters in these alloys, an intrinsic characteristic of the complex energy landscapes in CSAs.« less

Irradiation-induced damage evolution in concentrated Ni-based alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velisa, Gihan; Ullah, Mohammad Wali; Xue, Haizhou

Understanding the effects of chemical complexity from the number, type and concentration of alloying elements in single-phase concentred solid-solution alloys (SP-CSAs) on defect dynamics and microstructure evolution is pivotal for developing next-generation radiation-tolerant structural alloys. A specially chosen set of SP-CSAs with different chemical complexity (Ni 80Fe 20, Ni 80Cr 20 and Ni 40Fe 40Cr 20) are investigated using 1.5 MeV Mn ions over a wide fluence range, from 2 × 10 13 to 1 × 10 16 ions cm –2 at room temperature. Based on an integrated study of Rutherford backscattering spectroscopy in channeling geometry and molecular dynamics simulations,more » the results demonstrate that Ni 40Fe 40Cr 20 is more radiation tolerant than Ni 80Fe 20, Ni 80Cr 20 and elemental Ni in the low fluence regime. While chemical complexity of this set of SP-CSAs is clearly demonstrated to affect defect evolution through suppressed defect production and enhanced recombination at early stages, the effect of the mixed ferro- and anti-ferromagnetic interactions is not the only controlling factor responsible for the improved radiation performance. As a result, the observed strong alloying effect on defect evolution is attributed to the altered defect migration mobilities of defect clusters in these alloys, an intrinsic characteristic of the complex energy landscapes in CSAs.« less

Atomic-scale properties of Ni-based FCC ternary, and quaternary alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamm, Artur; Aabloo, Alvo; Klintenberg, Mattias

2015-08-26

The aim of our study is to characterize some atomic-scale properties of Ni-based FCC multicomponent alloys. For this purpose, we use Monte Carlo method combined with density functional theory calculations to study short-range order (SRO), atomic displacements, electronic density of states, and magnetic moments in equimolar ternary NiCrCo, and quaternary NiCrCoFe alloys. The salient features for the ternary alloy are a negative SRO parameter between Ni Cr and a positive between Cr Cr pairs as well as a weakly magnetic state. For the quaternary alloy we predict negative SRO parameter for Ni Cr and Ni Fe pairs and positive formore » Cr Cr and Fe Fe pairs. Atomic displacements for both ternary and quaternary alloys are negligible. In contrast to the ternary, the quaternary alloy shows a complex magnetic structure. The electronic structure of the ternary and quaternary alloys shows differences near the Fermi energy between a random solid solution and the predicted structure with SRO. Despite that, the calculated EXAFS spectra does not show enough contrast to discriminate between random and ordered structures. Finally, the predicted SRO has an impact on point-defect energetics, electron phonon coupling and thermodynamic functions and thus, SRO should not be neglected when studying properties of these two alloys.« less

Microstructure and magnetic behavior studies of processing-controlled and composition-modified Fe-Ni and Mn-Al alloys

NASA Astrophysics Data System (ADS)

Geng, Yunlong

L10-type (Space group P4/mmm) magnetic compounds, including FeNi and MnAl, possess promising technical magnetic properties of both high magnetization and large magnetocrystalline anisotropy energy, and thus offer potential in replacing rare earth permanent magnets in some applications. In equiatomic Fe-Ni, the disorder-order transformation from fcc structure to the L10 structure is a diffusional transformation, but is inhibited by the low ordering temperature. The transformation could be enhanced through the creation of vacancies. Thus, mechanical alloying was employed to generate more open-volume defects. A decrease in grain size and concomitant increase in grain boundary area resulted from the mechanical alloying, while an initial increase in internal strain (manifested through an increase in dislocation density) was followed by a subsequent decrease with further alloying. However, a decrease in the net defect concentration was determined by Doppler broadening positron annihilation spectroscopy, as open volume defects utilized dislocations and grain boundaries as sinks. An alloy, Fe32Ni52Zr3B13, formed an amorphous structure after rapid solidification, with a higher defect concentration than crystalline materials. Mechanical milling was utilized in an attempt to generate even more defects. However, it was observed that Fe32Ni52Zr3B13 underwent crystallization during the milling process, which appears to be related to enhanced vacancy-type defect concentrations allowing growth of pre-existing Fe(Ni) nuclei. The milling and enhanced vacancy concentration also de-stabilizes the glass, leading to decreased crystallization temperatures, and ultimately leading to complete crystallization. In Mn-Al, the L10 structure forms from the parent hcp phase. However, this phase is slightly hyperstoichiometric relative to Mn, and the excess Mn occupies Al sites and couples antiparallel to the other Mn atoms. In this study, the Zr substituted preferentially for the Mn atoms in the

Tungsten solution kinetics and amorphization of nickel in mechanically alloyed Ni-W alloys

NASA Technical Reports Server (NTRS)

Aning, A. O.; Wang, Z.; Courtney, T. H.

1993-01-01

The kinetics of solution of W, and the subsequent amorphization of Ni, in mechanically alloyed Ni-W alloys has been investigated. As W is a highly abrasive material in the energy intensive devices used for mechanical alloying, we studied the above reactions in different mills. One used hardened steel balls as the grinding media, and the other Al2O3. Abrasion is common to both mills, but Fe wear debris from the hardened steel enters into solution in the Ni rich phases whereas Al2O3 debris is present as small dispersoids. The kinetics of W solution and those of subsequent amorphization do not appear strongly affected by the Fe in solution or the Al2O3 dispersoid. Tungsten dissolves in crystalline Ni in amounts in excess of the equilibrium solubility during alloying. Amorphization of the Ni phase occurs if the W content in this phase exceeds ca. 28 at. pct.

NiFe nanoparticles: a soft magnetic material?

PubMed

Margeat, Olivier; Ciuculescu, Diana; Lecante, Pierre; Respaud, Marc; Amiens, Catherine; Chaudret, Bruno

2007-03-01

Polytetrahedral NiFe nanoparticles with diameters of (2.8+/-0.3) nm have been obtained by hydrogenation of Ni[(COD)(2)] (COD=1,5-cyclooctadiene) and Fe[{N(SiMe(3))(2)}(2)] at 150 degrees C using stearic acid and hexadecylamine as stabilizing ligands. The nanoparticles are superparamagnetic at room temperature and display a blocking temperature of 17.6 K. Their anisotropy (2.7x10(5)J m(-3)) is determined to be more than two orders of magnitude higher than that of the bulk NiFe alloy (10(3)J m(-3)) and is close to that determined for Fe nanoparticles of the same size. Still, they display a magnetization of (1.69+/-0.05) mu(B) per metallic atom, identical to that of the bulk NiFe alloy. Combining the results from X-ray absorption and Mössbauer studies, we evidence a progressive enrichment in iron atoms from the core to the surface of the nanoparticles. These results are discussed in relation to both size and chemical effects. They show the main role played by the enriched Fe surface on the magnetic properties and address the feasibility of soft magnetic materials at the nanoscale.

Effect of cathode vibration and heat treatment on electromagnetic properties of flake-shaped diatomite coated with Ni-Fe alloy by electroplating

NASA Astrophysics Data System (ADS)

Lan, Mingming; Li, Huiqin; Huang, Weihua; Xu, Guangyin; Li, Yan

2015-03-01

In this paper, flake-shaped diatomite particles were used as forming templates for the fabrication of the ferromagnetic functional fillers by way of electroplating Ni-Fe alloy method. The effects of cathode vibration frequency on the content of Ni-Fe alloy in the coating and the surface morphologies of the coatings were evaluated. The electromagnetic properties of the coated diatomite particles before and after heat treatment were also investigated in detail. The results show that the core-shell flake-shaped diatomite particles with high content of Ni-Fe alloy and good surface qualities of the coatings can be obtained by adjusting cathode vibration frequency. The coated diatomite particles with heat treatment filled paraffin wax composites exhibit a superior microwave absorbing and electromagnetic properties compared to the non-heat treated samples. Additionally, the peaks of reflection loss are found to be able to shift to lower frequency by the heat treatment process, which indicates the heat treatment can adjust microwave absorbing frequency band.

Synthesis and Magnetic Properties of Fe-Co-Ni/C Nanocomposites

NASA Astrophysics Data System (ADS)

Muratov, D. G.; Kozhitov, L. V.; Karpenkov, D. Yu.; Yakushko, E. V.; Korovin, E. Yu.; Vasil'ev, A. V.; Popkova, A. V.; Kazaryan, T. M.; Shadrinov, A. V.

2018-03-01

Nanoparticles of the Fe-Co-Ni ternary alloy, encapsulated in the carbon matrix of nanocomposites, have been synthesized, The structure, phase composition, and magnetic properties of the obtained materials have been determined with the help of diffractometry and magnetometry. It has been established that nanoparticles of the ternary alloy are formed due to solution of cobalt in the Fe-Ni alloy. The composition of the nanoparticles of the alloy depends on the mass percent ratio of the metas in the precursor. With growth of the iron content, nanoparticles of the ternary alloy with various composition are formed with FCC and BCC crystal lattice structure. As the synthesis temperature and relative iron content are increased, the magnetization of the Fe-Co-Ni/C nanocomposites increases from 26 to 157 A·m2/kg. The coercive force is determined by the synthesis temperature, the size of the nanoparticles, and the composition of the alloy, and its value varies from 330 to 43 Oe.

Allotropic forms of carbon in the Invar Fe-Ni-C alloy before and after plastic deformation by upsetting

NASA Astrophysics Data System (ADS)

Nadutov, V. M.; Vashchuk, D. L.; Karbivskii, V. L.; Volosevich, P. Yu.; Davydenko, O. A.

2018-04-01

The effect of cold plastic deformation by upsetting (e = 1.13) on structure and hybridised bonds of carbon in the fcc Invar Fe-30.9%Ni-1.23% C alloy was studied by means of X-ray phase analysis and X-ray photoelectron spectroscopy. Carbon precipitates along grain boundaries and inside of grains in the alloy after annealing and plastic deformation were revealed. The presence of mainly sp2- and sp3-hybridised C-C bonds attributing to graphite and amorphous carbon as well as the carbon bonds with impurity atoms and metallic Fe and Ni atoms in austenitic phase were revealed in the annealed and deformed alloy. It was shown for the first time that plastic deformation of the alloy results in partial destruction of the graphite crystal structure, increasing the relative part of amorphous carbon, and redistribution of carbon between structural elements as well as in a solid solution of austenitic phase.

Characterization of Magnetic NiFe Nanoparticles with Controlled Bimetallic Composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yan; Chi, Yanxiu; Shan, Shiyao

2014-02-25

The exploration of the magnetic properties of bimetallic alloy nanoparticles for various technological applications requires the ability to control the morphology, composition, and surface properties. In this report, we describe new findings of an investigation of the morphology and composition of NiFe alloy nanoparticles synthesized under controlled conditions. The controllability over the bimetallic composition has been demonstrated by the observation of an approximate linear relationship between the composition in the nanoparticles and in the synthetic feeding. The morphology of the NiFe nanoparticles is consistent with an fcc-type alloy, with the lattice strain increasing linearly with the iron content in themore » nanoparticles. The alloy nanoparticles exhibit remarkable resistance to air oxidation in comparison with Ni or Fe particles. The thermal stability and the magnetic properties of the as-synthesized alloy nanoparticles are shown to depend on the composition. The alloy nanoparticles have also be sown to display low saturation magnetization and coercivity values in comparison with the Ni nanoparticles, in line with the superparamagnetic characteristic. These findings have important implications for the design of stable and controllable magnetic nanoparticles for various technological applications.« less

Magnetic properties of the CrMnFeCoNi high-entropy alloy

DOE PAGES

Schneeweiss, Oldřich; Friák, Martin; Dudová, Marie; ...

2017-07-28

In this paper, we present experimental data showing that the equiatomic CrMnFeCoNi high-entropy alloy undergoes two magnetic transformations at temperatures below 100 K while maintaining its fcc structure down to 3 K. The first transition, paramagnetic to spin glass, was detected at 93 K and the second transition of the ferromagnetic type occurred at 38 K. Field-assisted cooling below 38 K resulted in a systematic vertical shift of the hysteresis curves. Strength and direction of the associated magnetization bias was proportional to the strength and direction of the cooling field and shows a linear dependence with a slope of 0.006more » ± 0.001 emu T. The local magnetic moments of individual atoms in the CrMnFeCoNi quinary fcc random solid solution were investigated by ab initio (electronic density functional theory) calculations. Results of the numerical analysis suggest that, irrespective of the initial configuration of local magnetic moments, the magnetic moments associated with Cr atoms align antiferromagnetically with respect to a cumulative magnetic moment of their first coordination shell. The ab initio calculations further showed that the magnetic moments of Fe and Mn atoms remain strong (between 1.5 and 2 μ B), while the local moments of Ni atoms effectively vanish. Finally, these results indicate that interactions of Mn- and/or Fe-located moments with the surrounding magnetic structure account for the observed macroscopic magnetization bias.« less

GeV ion irradiation of NiFe and NiCo: Insights from MD simulations and experiments

DOE PAGES

Leino, Aleksi A.; Samolyuk, German D.; Sachan, Ritesh; ...

2018-03-31

Concentrated solid solution alloys have attracted rapidly increasing attention due to their potential for designing materials with high tolerance to radiation damage. To tackle the effects of chemical complexity in defect dynamics and radiation response, we present in this paper a computational study on swift heavy ion induced effects in Ni and equiatomic Ni -based alloys (Ni 50Fe 50, Ni 50Co 50) using two-temperature molecular dynamics simulations (2T-MD). The electronic heat conductivity in the two-temperature equations is parameterized from the results of first principles electronic structure calculations. A bismuth ion (1.542 GeV) is selected and single impact simulations performed inmore » each target. We study the heat flow in the electronic subsystem and show that alloying Ni with Co or Fe reduces the heat dissipation from the impact by the electronic subsystem. Simulation results suggest no melting or residual damage in pure Ni while a cylindrical region melts along the ion propagation path in the alloys. In Ni 50Co 50 the damage consists of a dislocation loop structure (d = 2 nm) and isolated point defects, while in Ni 50Fe 50, a defect cluster (d = 4 nm) along the ion path is, in addition, formed. The simulation results are supported by atomic-level structural and defect characterizations in bismuth-irradiated Ni and Ni 50Fe 50. Finally, the significance of the 2T-MD model is demonstrated by comparing the results to those obtained with an instantaneous energy deposition model without consideration of e-ph interactions in pure Ni and by showing that it leads to a different qualitative behavior.« less

GeV ion irradiation of NiFe and NiCo: Insights from MD simulations and experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leino, Aleksi A.; Samolyuk, German D.; Sachan, Ritesh

Concentrated solid solution alloys have attracted rapidly increasing attention due to their potential for designing materials with high tolerance to radiation damage. To tackle the effects of chemical complexity in defect dynamics and radiation response, we present in this paper a computational study on swift heavy ion induced effects in Ni and equiatomic Ni -based alloys (Ni 50Fe 50, Ni 50Co 50) using two-temperature molecular dynamics simulations (2T-MD). The electronic heat conductivity in the two-temperature equations is parameterized from the results of first principles electronic structure calculations. A bismuth ion (1.542 GeV) is selected and single impact simulations performed inmore » each target. We study the heat flow in the electronic subsystem and show that alloying Ni with Co or Fe reduces the heat dissipation from the impact by the electronic subsystem. Simulation results suggest no melting or residual damage in pure Ni while a cylindrical region melts along the ion propagation path in the alloys. In Ni 50Co 50 the damage consists of a dislocation loop structure (d = 2 nm) and isolated point defects, while in Ni 50Fe 50, a defect cluster (d = 4 nm) along the ion path is, in addition, formed. The simulation results are supported by atomic-level structural and defect characterizations in bismuth-irradiated Ni and Ni 50Fe 50. Finally, the significance of the 2T-MD model is demonstrated by comparing the results to those obtained with an instantaneous energy deposition model without consideration of e-ph interactions in pure Ni and by showing that it leads to a different qualitative behavior.« less

Design of ultrathin Pt-Mo-Ni nanowire catalysts for ethanol electrooxidation.

PubMed

Mao, Junjie; Chen, Wenxing; He, Dongsheng; Wan, Jiawei; Pei, Jiajing; Dong, Juncai; Wang, Yu; An, Pengfei; Jin, Zhao; Xing, Wei; Tang, Haolin; Zhuang, Zhongbin; Liang, Xin; Huang, Yu; Zhou, Gang; Wang, Leyu; Wang, Dingsheng; Li, Yadong

2017-08-01

Developing cost-effective, active, and durable electrocatalysts is one of the most important issues for the commercialization of fuel cells. Ultrathin Pt-Mo-Ni nanowires (NWs) with a diameter of ~2.5 nm and lengths of up to several micrometers were synthesized via a H 2 -assisted solution route (HASR). This catalyst was designed on the basis of the following three points: (i) ultrathin NWs with high numbers of surface atoms can increase the atomic efficiency of Pt and thus decrease the catalyst cost; (ii) the incorporation of Ni can isolate Pt atoms on the surface and produce surface defects, leading to high catalytic activity (the unique structure and superior activity were confirmed by spherical aberration-corrected electron microscopy measurements and ethanol oxidation tests, respectively); and (iii) the incorporation of Mo can stabilize both Ni and Pt atoms, leading to high catalytic stability, which was confirmed by experiments and density functional theory calculations. Furthermore, the developed HASR strategy can be extended to synthesize a series of Pt-Mo-M (M = Fe, Co, Mn, Ru, etc.) NWs. These multimetallic NWs would open up new opportunities for practical fuel cell applications.

Design of ultrathin Pt-Mo-Ni nanowire catalysts for ethanol electrooxidation

PubMed Central

Mao, Junjie; Chen, Wenxing; He, Dongsheng; Wan, Jiawei; Pei, Jiajing; Dong, Juncai; Wang, Yu; An, Pengfei; Jin, Zhao; Xing, Wei; Tang, Haolin; Zhuang, Zhongbin; Liang, Xin; Huang, Yu; Zhou, Gang; Wang, Leyu; Wang, Dingsheng; Li, Yadong

2017-01-01

Developing cost-effective, active, and durable electrocatalysts is one of the most important issues for the commercialization of fuel cells. Ultrathin Pt-Mo-Ni nanowires (NWs) with a diameter of ~2.5 nm and lengths of up to several micrometers were synthesized via a H2-assisted solution route (HASR). This catalyst was designed on the basis of the following three points: (i) ultrathin NWs with high numbers of surface atoms can increase the atomic efficiency of Pt and thus decrease the catalyst cost; (ii) the incorporation of Ni can isolate Pt atoms on the surface and produce surface defects, leading to high catalytic activity (the unique structure and superior activity were confirmed by spherical aberration–corrected electron microscopy measurements and ethanol oxidation tests, respectively); and (iii) the incorporation of Mo can stabilize both Ni and Pt atoms, leading to high catalytic stability, which was confirmed by experiments and density functional theory calculations. Furthermore, the developed HASR strategy can be extended to synthesize a series of Pt-Mo-M (M = Fe, Co, Mn, Ru, etc.) NWs. These multimetallic NWs would open up new opportunities for practical fuel cell applications. PMID:28875160

Surface tension measurement of undercooled liquid Ni-based multicomponent alloys

NASA Astrophysics Data System (ADS)

Chang, J.; Wang, H. P.; Zhou, K.; Wei, B.

2012-09-01

The surface tensions of liquid ternary Ni-5%Cu-5%Fe, quaternary Ni-5%Cu-5%Fe-5%Sn and quinary Ni-5%Cu-5%Fe-5%Sn-5%Ge alloys were determined as a function of temperature by the electromagnetic levitation oscillating drop method. The maximum undercoolings obtained in the experiments are 272 (0.15T L), 349 (0.21T L) and 363 K (0.22T L), respectively. For all the three alloys, the surface tension decreases linearly with the rise of temperature. The surface tension values are 1.799, 1.546 and 1.357 N/m at their liquidus temperatures of 1719, 1644 and 1641 K. Their temperature coefficients are -4.972 × 10-4, -5.057 × 10-4 and -5.385 × 10-4 N/m/K. It is revealed that Sn and Ge are much more efficient than Cu and Fe in reducing the surface tension of Ni-based alloys. The addition of Sn can significantly enlarge the maximum undercooling at the same experimental condition. The viscosity of the three undercooled liquid alloys was also derived from the surface tension data.

High pressure synthesis of a hexagonal close-packed phase of the high-entropy alloy CrMnFeCoNi

NASA Astrophysics Data System (ADS)

Tracy, Cameron L.; Park, Sulgiye; Rittman, Dylan R.; Zinkle, Steven J.; Bei, Hongbin; Lang, Maik; Ewing, Rodney C.; Mao, Wendy L.

2017-05-01

High-entropy alloys, near-equiatomic solid solutions of five or more elements, represent a new strategy for the design of materials with properties superior to those of conventional alloys. However, their phase space remains constrained, with transition metal high-entropy alloys exhibiting only face- or body-centered cubic structures. Here, we report the high-pressure synthesis of a hexagonal close-packed phase of the prototypical high-entropy alloy CrMnFeCoNi. This martensitic transformation begins at 14 GPa and is attributed to suppression of the local magnetic moments, destabilizing the initial fcc structure. Similar to fcc-to-hcp transformations in Al and the noble gases, the transformation is sluggish, occurring over a range of >40 GPa. However, the behaviour of CrMnFeCoNi is unique in that the hcp phase is retained following decompression to ambient pressure, yielding metastable fcc-hcp mixtures. This demonstrates a means of tuning the structures and properties of high-entropy alloys in a manner not achievable by conventional processing techniques.

Ultra-thin L1{sub 0}-FePt for perpendicular anisotropy L1{sub 0}-FePt/Ag/[Co/Pd]{sub 30} pseudo spin valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Pin; Chow, Gan Moog; Chen, Jing-Sheng, E-mail: msecj@nus.edu.sg

2014-05-07

Perpendicular anisotropy L1{sub 0}-FePt/Ag/[Co/Pd]{sub 30} pseudo spin valves (PSVs) with ultra-thin L1{sub 0}-FePt alloy free layer possessing high anisotropy and thermal stability have been fabricated and studied. The thickness of the L1{sub 0}-FePt layer was varied between 2 and 4 nm. The PSV became increasingly decoupled with reduced L1{sub 0}-FePt thickness due to the larger difference between the coercivity of the L1{sub 0}-FePt and [Co/Pd]{sub 30} films. The PSV with an ultra-thin L1{sub 0}-FePt free layer of 2 nm displayed a high K{sub u} of 2.21 × 10{sup 7} ergs/cm{sup 3}, high thermal stability of 84 and a largest giant magnetoresistance of 0.54%.

Analysis of Microstructure and Sliding Wear Behavior of Co1.5CrFeNi1.5Ti0.5 High-Entropy Alloy

NASA Astrophysics Data System (ADS)

Lentzaris, K.; Poulia, A.; Georgatis, E.; Lekatou, A. G.; Karantzalis, A. E.

2018-04-01

Α Co1.5CrFeNi1.5Ti0.5 high-entropy alloy (HEA) of the well-known family of CoCrFeNiTi has been designed using empirical parameters. The aim of this design was the production of a HEA with fcc structure that gives ductile behavior and also high strength because of the solid solution effect. The VEC calculations (8.1) supported the fcc structure while the δ factor calculations (4.97) not being out of the limit values, advised a significant lattice distortion. From the other hand, the ΔΗ mix calculations (- 9.64 kJ/mol) gave strong indications that no intermetallic would be formed. In order to investigate its potential application, the Co1.5CrFeNi1.5Ti0.5 HEA was prepared by vacuum arc melting and a primary assessment of its surface degradation response was conducted by means of sliding wear testing using different counterbody systems for a total sliding distance of 1000 m. An effort to correlate the alloy's wear response with the microstructural characteristics was attempted. Finally, the wear behavior of the Co1.5CrFeNi1.5Ti0.5 HEA was compared with that of two commercially used wear-resistant alloys. The results obtained provided some first signs of the high-entropy alloys' better wear performance when tested under sliding conditions against a steel ball.

Enhanced thermal stability of Cu alloy films by strong interaction between Ni and Zr (or Fe)

NASA Astrophysics Data System (ADS)

Zheng, Yuehong; Li, Xiaona; Cheng, Xiaotian; Li, Zhuming; Liu, Yubo; Dong, Chuang

2018-04-01

Low resistivity, phase stability and nonreactivity with surrounding dielectrics are the key to the application of Cu to ultra-large-scale integrated circuits. Here, a stable solid solution cluster model was introduced to design the composition of barrierless Cu-Ni-Zr (or Fe) seed layers. The third elements Fe and Zr were dissolved into Cu via a second element Ni, which is soluble in both Cu and Zr (or Fe). The films were prepared by magnetron sputtering on the single-crystal p-Si (1 0 0) wafers. Since the diffusion characteristics of the alloying elements are different, the effects of the strong interaction between Ni and Zr (or Fe) on the film’s stability and resistivity were studied. The results showed that a proper addition of Zr-Ni (Zr/Ni  ⩽  0.6/12) into Cu could form a large negative lattice distortion, which inhibits Cu-Si interdiffusion and enhances the stability of Cu film. When Fe-Ni was co-added into Cu, the lattice distortion of Cu reached a lower value, 0.0029 Å  ⩽  |Δa|  ⩽  0.0046 Å, and the films showed poor stability. Therefore, when the model is applied to the composition design of the films, the strong interaction between the elements and the addition ratio should be taken into consideration.

Magnetic properties of CoNiFe alloys electrodeposited under potential and current control conditions

NASA Astrophysics Data System (ADS)

Perez, L.; Attenborough, K.; De Boeck, J.; Celis, J. P.; Aroca, C.; Sánchez, P.; López, E.; Sánchez, M. C.

2002-04-01

Electrodeposited CoNiFe alloys have been produced under potential and current control conditions. It was found that composition, crystalline structure and magnetic properties are the same irrespective of which plating control is used. Magnetic anisotropy is present in the softest samples. A study of the dependence of magnetic properties and domain structure on the thickness of the films is also reported.

Microstructure and Mechanical Properties Evolution of the Al, C-Containing CoCrFeNiMn-Type High-Entropy Alloy during Cold Rolling.

PubMed

Klimova, Margarita; Stepanov, Nikita; Shaysultanov, Dmitry; Chernichenko, Ruslan; Yurchenko, Nikita; Sanin, Vladimir; Zherebtsov, Sergey

2017-12-29

The effect of cold rolling on the microstructure and mechanical properties of an Al- and C-containing CoCrFeNiMn-type high-entropy alloy was reported. The alloy with a chemical composition (at %) of (20-23) Co, Cr, Fe, and Ni; 8.82 Mn; 3.37 Al; and 0.69 C was produced by self-propagating high-temperature synthesis with subsequent induction. In the initial as-cast condition the alloy had an face centered cubic single-phase coarse-grained structure. Microstructure evolution was mostly associated with either planar dislocation glide at relatively low deformation during rolling (up to 20%) or deformation twinning and shear banding at higher strain. After 80% reduction, a heavily deformed twinned/subgrained structure was observed. A comparison with the equiatomic CoCrFeNiMn alloy revealed higher dislocation density at all stages of cold rolling and later onset of deformation twinning that was attributed to a stacking fault energy increase in the program alloy; this assumption was confirmed by calculations. In the initial as-cast condition the alloy had low yield strength of 210 MPa with yet very high uniform elongation of 74%. After 80% rolling, yield strength approached 1310 MPa while uniform elongation decreased to 1.3%. Substructure strengthening was found to be dominated at low rolling reductions (<40%), while grain (twin) boundary strengthening prevailed at higher strains.

The elastic properties and stability of fcc-Fe and fcc-FeNi alloys at inner-core conditions

NASA Astrophysics Data System (ADS)

Martorell, Benjamí; Brodholt, John; Wood, Ian G.; Vočadlo, Lidunka

2015-07-01

The agreement between shear wave velocities for the Earth's inner core observed from seismology with those derived from mineral physics is considerably worse than for any other region of the Earth. Furthermore, there is still debate as to the phase of iron present in the inner core, particularly when alloying with nickel and light elements is taken into account. To investigate the extent to which the mismatch between seismology and mineral physics is a function of either crystal structure and/or the amount of nickel present, we have used ab initio molecular dynamics simulations to calculate the elastic constants and seismic velocities (Vp and Vs) of face centred cubic (fcc) iron at Earth's inner core pressures (360 GPa) and at temperatures up to ˜7000 K. We find that Vp for fcc iron (fcc-Fe) is very similar to that for hexagonal close packed (hcp) iron at all temperatures. In contrast, Vs for fcc-Fe is significantly higher than in hcp-Fe, with the difference increasing with increasing temperature; the difference between Vs for the core (from seismology) and Vs for fcc-Fe exceeds 40 per cent. These results are consistent with previous work at lower temperatures. We have also investigated the effect of 6.5 and 13 atm% Ni in fcc-Fe. We find that Ni only slightly reduces Vp and Vs (e.g. by 2 per cent in Vs for 13 atm% Ni at 5500 K), and cannot account for the difference between the velocities observed in the core and those of pure fcc-Fe. We also tried to examine pre-melting behaviour in fcc-Fe, as reported in hcp-Fe by extending the study to very high temperatures (at which superheating may occur). However, we find that fcc-Fe spontaneously transforms to other hcp-like structures before melting; two hcp-like structures were found, both of hexagonal symmetry, which may most easily be regarded as being derived from an hcp crystal with stacking faults. That the structure did not transform to a true hcp phase is likely as a consequence of the limited size of the

Damage structures in fission-neutron irradiated Ni-based alloys at high temperatures

NASA Astrophysics Data System (ADS)

Yamakawa, K.; Shimomura, Y.

1999-01-01

The defects formed in Ni based (Ni-Si, Ni-Cu and Ni-Fe) alloys which were irradiated with fission-neutrons were examined by electron microscopy. Irradiations were carried out at 473 K and 573 K. In the 473 K irradiated specimens, a high density of large interstitial loops and small vacancy clusters with stacking fault tetrahedra (SFT) were observed. The number densities of these two types of defects did not strongly depend on the amount of solute atoms in each alloy. The density of the loops in Ni-Si alloys was much higher than those in Ni-Cu and Ni-Fe alloys, while the density of SFT only slightly depended on the kind of solute. Also, the size of the loops depended on the kinds and amounts of solute. In 573 K irradiated Ni-Cu specimens, a high density of dislocation lines developed during the growth of interstitial loops. In Ni-Si alloys, the number density and size of the interstitial loops changed as a function of the amount of solute. Voids were formed in Ni-Cu alloys but scarcely formed in Ni-Si alloys. The number density of voids was one hundredth of that of SFT observed in 473 K irradiated Ni-Cu alloys. Possible formation processes of interstitial loops, SFT dislocation lines and voids are discussed.

Atomistic clustering-ordering and high-strain deformation of an Al 0.1CrCoFeNi high-entropy alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Aayush; Singh, Prashant; Johnson, Duane D.

2016-08-08

Here, computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived propertiesmore » are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study Al xCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al 0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al 0.1CrCoFeNi.« less

Atomistic clustering-ordering and high-strain deformation of an Al0.1CrCoFeNi high-entropy alloy

PubMed Central

Sharma, Aayush; Singh, Prashant; Johnson, Duane D.; Liaw, Peter K.; Balasubramanian, Ganesh

2016-01-01

Computational investigations of structural, chemical, and deformation behavior in high-entropy alloys (HEAs), which possess notable mechanical strength, have been limited due to the absence of applicable force fields. To extend investigations, we propose a set of intermolecular potential parameters for a quinary Al-Cr-Co-Fe-Ni alloy, using the available ternary Embedded Atom Method and Lennard-Jones potential in classical molecular-dynamics simulations. The simulation results are validated by a comparison to first-principles Korringa-Kohn-Rostoker (KKR) - Coherent Potential Approximation (CPA) [KKR-CPA] calculations for the HEA structural properties (lattice constants and bulk moduli), relative stability, pair probabilities, and high-temperature short-range ordering. The simulation (MD)-derived properties are in quantitative agreement with KKR-CPA calculations (first-principles) and experiments. We study AlxCrCoFeNi for Al ranging from 0 ≤ x ≤2 mole fractions, and find that the HEA shows large chemical clustering over a wide temperature range for x < 0.5. At various temperatures high-strain compression promotes atomistic rearrangements in Al0.1CrCoFeNi, resulting in a clustering-to-ordering transition that is absent for tensile loading. Large fluctuations under stress, and at higher temperatures, are attributed to the thermo-plastic instability in Al0.1CrCoFeNi. PMID:27498807

Development of Computational Tools for Modeling Thermal and Radiation Effects on Grain Boundary Segregation and Precipitation in Fe-Cr-Ni-based Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ying

This work aims at developing computational tools for modeling thermal and radiation effects on solute segregation at grain boundaries (GBs) and precipitation. This report described two major efforts. One is the development of computational tools on integrated modeling of thermal equilibrium segregation (TES) and radiation-induced segregation (RIS), from which synergistic effects of thermal and radiation, pre-existing GB segregation have been taken into consideration. This integrated modeling was used in describing the Cr and Ni segregation in the Fe-Cr-Ni alloys. The other effort is thermodynamic modeling on the Fe-Cr-Ni-Mo system which includes the major alloying elements in the investigated alloys inmore » the Advanced Radiation Resistant Materials (ARRM) program. Through thermodynamic calculation, we provide baseline thermodynamic stability of the hardening phase Ni2(Cr,Mo) in selected Ni-based super alloys, and contribute knowledge on mechanistic understanding on the formation of Ni2(Cr,Mo) in the irradiated materials. The major outcomes from this work are listed in the following: 1) Under the simultaneous thermal and irradiation conditions, radiation-induced segregation played a dominant role in the GB segregation. The pre-existing GB segregation only affects the subsequent radiation-induced segregation in the short time. For the same element, the segregation tendency of Cr and Ni due to TES is opposite to it from RIS. The opposite tendency can lead to the formation of W-shape profile. These findings are consistent with literature observation of the transitory W-shape profile. 2) While TES only affects the distance of one or two atomic layers from GBs, the RIS can affect a broader distance from GB. Therefore, the W-shape due to pre-existing GB segregation is much narrower than that due to composition gradient formed during the transient state. Considering the measurement resolution of Auger or STEM analysis, the segregation tendency due to RIS should play a

Influence of the chemical composition of rapidly quenched amorphous alloys (Ni, Fe, Cr)-B-Si on its crystallization process

NASA Astrophysics Data System (ADS)

Elmanov, G.; Dzhumaev, P.; Ivanitskaya, E.; Skrytnyi, V.; Ruslanov, A.

2016-04-01

This paper presents results of research of the structure and phase transformations during the multistage crystallization of the metallic glasses with the compositions Ni71,5Cr6,8Fe2,7B11,9Si7,1 and Ni63,4Cr7,4Fe4,3Mn0,8B15,6Si8,5 labeled as AWS BNi-2 according to American Welding Society. Differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX) were used as experimental research methods. The influence of the alloys chemical composition (boron, manganese and iron) on the temperatures and the exothermic heat effects of phase transformations, as well as on the phase composition of alloys at three stages of crystallization was analyzed. We present a thermodynamic explanation of the observed heat effects. It has been shown that manganese has the main influence on the phase transformations temperatures and heat effects in these two alloys. It is also assumed that at the final crystallization stage simultaneously with the formation of phases Ni3B and β1-Ni3Si should occur the nucleation of borides of CrB type with high Cr and low Si content.

Features of primary damage by high energy displacement cascades in concentrated Ni-based alloys

DOE PAGES

Béland, Laurent Karim; Lu, Chenyang; Osetskiy, Yuri N.; ...

2016-02-25

Alloying of Ni with Fe or Co reduces primary damage production under ion irradiation. Similar results have been obtained from classical molecular dynamics simulations of 1, 10, 20, and 40 keV collision cascades in Ni, NiFe, and NiCo. In all cases, a mix of imperfect stacking fault tetrahedra, faulted loops with a 1/3 {111} Burgers vector, and glissile interstitial loops with a 1/2 {110} Burgers vector were formed, along with small sessile point defect complexes and clusters. Primary damage reduction occurs by three mechanisms. First, Ni-Co, Ni-Fe, Co-Co, and Fe-Fe short-distance repulsive interactions are stiffer than Ni-Ni interactions, which leadmore » to a decrease in damage formation during the transition from the supersonic ballistic regime to the sonic regime. This largely controls final defect production. Second, alloying decreases thermal conductivity, leading to a longer thermal spike lifetime. The associated annealing reduces final damage production. These two mechanisms are especially important at cascades energies less than 40 keV. Third, at the higher energies, the production of large defect clusters by subcascades is inhibited in the alloys. A number of challenges and limitations pertaining to predictive atomistic modeling of alloys under high-energy particle irradiation are discussed.« less

Oxide Scales Formed on NiTi and NiPtTi Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Smialek, James L.; Garg, Anita; Rogers, Richard B.; Noebe, Ronald D.

2011-01-01

Ni-49Ti and Ni-30Pt-50Ti (at.%) shape memory alloys were oxidized isothermally in air over the temperature range of 500 to 900 C. The microstructure, composition, and phase content of the scales were studied by SEM, EDS, XRD, and metallography. Extensive plan view SEM/EDS identified various features of intact or spalled scale surfaces. The outer surface of the scale was a relatively pure TiO2 rutile structure, typified by a distinct highly striated and faceted crystal morphology. Crystal size increased significantly with temperature. Spalled regions exhibited some porosity and less distinct features. More detailed information was obtained by correlation of SEM/EDS studies of 700 C/100 hr cross-sections with XRD analyses of serial or taper-polishing of plan surfaces. Overall, multiple layers exhibited graded mixtures of NiO, TiO2, NiTiO3, Ni(Ti) or Pt(Ni,Ti) metal dispersoids, Ni3Ti or Pt3Ti depletion zones, and substrate, in that order. The NiTi alloy contained a 3 at.% Fe impurity that appeared in embedded localized Fe-Ti-rich oxides, while the NiPtTi alloy contained a 2 v/o dispersion of TiC that appeared in lower layers. The oxidation kinetics of both alloys (in a previous report) indicated parabolic growth and an activation energy (250 kJ/mole) near those reported in other Ti and NiTi studies. This is generally consistent with TiO2 existing as the primary scale constituent, as described here.

Study of structural phase transitions in quinary TiNi(MoFeAg)-based alloys

NASA Astrophysics Data System (ADS)

Gunther, Victor; Marchenko, Ekaterina; Chekalkin, Timofey; Baigonakova, Gulsharat; Kang, Ji-hoon; Kim, Ji-soon; Klopotov, Anatoliy

2017-10-01

The structural phase transitions of quinary Ti50Ni49.5-X Mo0.3Fe0.2Ag X (X  =  0, 0.1, 0.2, 0.5, 1.0, and 1.5 at%) alloys prepared by vacuum-induction melting were studied by means of the four-point-probe, x-ray diffraction (XRD), and optical microscopy methods after thermal cycling. The two-stage B2 ↔ R ↔ B19‧ reversible martensitic transformation (MT) took place in all the investigated samples. It is found that the substitution of Ag for Ni in the studied alloy when C Ag  =  0-0.5 at%, reduces the T R, M s, and M f characteristic points by 20-30 K, whereas they increase by 15-35 K when the Ag content was varied from 1.0 to 1.5 at% and the B2 ↔ R ↔ B19‧ MT was realized in the high-temperature area. XRD patterns of the studied alloys recorded at the ambient temperature detected the pure Ag phase as well as Ti2Ni precipitate with a small volume fraction (up to 5%) alongside with structural lines of B2, R, and B19‧ phases.

Enhanced magnetic moment in ultrathin Fe-doped CoFe2O4 films

NASA Astrophysics Data System (ADS)

Moyer, J. A.; Vaz, C. A. F.; Kumah, D. P.; Arena, D. A.; Henrich, V. E.

2012-11-01

The effect of film thickness on the magnetic properties of ultrathin Fe-doped cobalt ferrite (Co1-xFe2+xO4) grown on MgO (001) substrates is investigated by superconducting quantum interference device magnetometry and x-ray magnetic linear dichroism, while the distribution of the Co2+ cations between the octahedral and tetrahedral lattice sites is studied with x-ray absorption spectroscopy. For films thinner than 10 nm, there is a large enhancement of the magnetic moment; conversely, the remanent magnetization and coercive fields both decrease, while the magnetic spin axes of all the cations become less aligned with the [001] crystal direction. In particular, at 300 K the coercive fields of the thinnest films vanish. The spectroscopy data show that no changes occur in the cation distribution as a function of film thickness, ruling this out as the origin of the enhanced magnetic moment. However, the magnetic measurements all support the possibility that these ultrathin Fe-doped CoFe2O4 films are transitioning into a superparamagnetic state, as has been seen in ultrathin Fe3O4. A weakening of the magnetic interactions at the antiphase boundaries, leading to magnetically independent domains within the film, could explain the enhanced magnetic moment in ultrathin Fe-doped CoFe2O4 and the onset of superparamagnetism at room temperature.

The Role of Carbon in Grain Refinement of Cast CrFeCoNi High-Entropy Alloys

NASA Astrophysics Data System (ADS)

Liu, X. W.; Liu, L.; Liu, G.; Wu, X. X.; Lu, D. H.; Yao, J. Q.; Jiang, W. M.; Fan, Z. T.; Zhang, W. B.

2018-03-01

As a promising engineering material, high-entropy alloys (HEAs) CrFeCoNi system has attracted extensive attention worldwide. Their cast alloys are of great importance because of their great formability of complex components, which can be further improved through the transition of the columnar to equiaxed grains and grain refinement. In the current work, the influence of C contents on the grain structures and mechanical properties of the as-cast high-entropy alloy CrFeCoNi was chosen as the target and systematically studied via a hybrid approach of the experiments and thermodynamic calculations. The alloys with various C additions were prepared by arc melting and drop cast. The as-cast macrostructure and microstructure were characterized using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The cast HEAs transform from coarse columnar grains into equiaxed grains with the C level increased to ≥ 2 at. pct and the size of equiaxed grains is further decreased with the increasing C addition. It is revealed that the interdendritic segregation of Cr and C results in grain boundary precipitation of M23C6 carbides. The grain refinement is attributed to the additional constitutional supercoiling from the C addition. The yield stress and tensile strength at room temperature are improved due to the transition of columnar to equiaxed grains and grain refinement.

The Role of Carbon in Grain Refinement of Cast CrFeCoNi High-Entropy Alloys

NASA Astrophysics Data System (ADS)

Liu, X. W.; Liu, L.; Liu, G.; Wu, X. X.; Lu, D. H.; Yao, J. Q.; Jiang, W. M.; Fan, Z. T.; Zhang, W. B.

2018-06-01

As a promising engineering material, high-entropy alloys (HEAs) CrFeCoNi system has attracted extensive attention worldwide. Their cast alloys are of great importance because of their great formability of complex components, which can be further improved through the transition of the columnar to equiaxed grains and grain refinement. In the current work, the influence of C contents on the grain structures and mechanical properties of the as-cast high-entropy alloy CrFeCoNi was chosen as the target and systematically studied via a hybrid approach of the experiments and thermodynamic calculations. The alloys with various C additions were prepared by arc melting and drop cast. The as-cast macrostructure and microstructure were characterized using optical microscopy, scanning electron microscopy, and transmission electron microscopy. The cast HEAs transform from coarse columnar grains into equiaxed grains with the C level increased to ≥ 2 at. pct and the size of equiaxed grains is further decreased with the increasing C addition. It is revealed that the interdendritic segregation of Cr and C results in grain boundary precipitation of M23C6 carbides. The grain refinement is attributed to the additional constitutional supercoiling from the C addition. The yield stress and tensile strength at room temperature are improved due to the transition of columnar to equiaxed grains and grain refinement.

Ferromagnetic resonance investigation in as-prepared NiFe/FeMn/NiFe trilayer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, S. J.; Xu, K.; Yu, L. M.

2007-06-01

NiFe/FeMn/NiFe trilayer prepared by dc magnetron sputtering was systematically investigated by ferromagnetic resonance technique (FMR) at room temperature. For NiFe/FeMn/NiFe trilayer, there are two distinct resonance peaks both in in-plane and out-of-plane FMR spectra, which are attributed to the two NiFe layers, respectively. The isotropic in-plane resonance field shift is negative for the bottom NiFe layer, while positive for the top NiFe layer. And, such phenomena result from the negative interfacial perpendicular anisotropy at the bottom NiFe/FeMn interface and positive interfacial perpendicular anisotropy at the top FeMn/NiFe interface. The linewidth of the bottom NiFe layer is larger than that ofmore » the top NiFe layer, which might be related to the greater exchange coupling at the bottom NiFe/FeMn interface.« less

Performance of chromia- and alumina-forming Fe- and Ni-base alloys exposed to metal dusting environments: The effect of water vapor and temperature

DOE PAGES

Rouaix-Vande Put, Aurelie; Unocic, Kinga A.; Brady, Michael P.; ...

2015-11-18

Fe- and Ni-base alloys including an alumina-forming austenitic alloy were exposed for 500 h under metal dusting environments with varying temperature, gas composition and total pressure. For one H 2–CO–CO 2–H 2O environment, the increase in temperature from 550 to 750 °C generally decreased metal dusting. When H 2O was added to a H 2–CO–CO 2 environment at 650 °C, the metal dusting attack was reduced. Even after 5000 h at a total pressure of 9.1 atm with 20%H 2O, the higher alloyed specimens retained a thin protective oxide. Lastly, for gas mixtures containing little or no H 2O, themore » Fe-base alloys were less resistant to metal dusting than Ni-base alloys.« less

Structural and magnetic properties of FexNi100-x alloys synthesized using Al as a reducing metal

NASA Astrophysics Data System (ADS)

Srakaew, N.; Jantaratana, P.; Nipakul, P.; Sirisathitkul, C.

2017-08-01

Iron-nickel (Fe-Ni) alloys comprising nine different compositions were rapidly synthesized from the redox reaction using aluminum foils as the reducing metal. Compared with conventional chemical syntheses, this simple approach is relatively safe and allows control over the alloy morphology and magnetic behavior as a function of the alloy composition with minimal oxidation. For alloys having low (10%-30%) Fe content the single face-centered cubic (FCC) FeNi3 phase was formed with nanorods aligned in the (1 1 1) crystalline direction on the cluster surface. This highly anisotropic morphology gradually disappeared as the Fe content was raised to 40%-70% with the alloy structure possessing a mixture of FCC FeNi3 and body-centered cubic (BCC) Fe7Ni3. The FCC phase was entirely replaced by the BCC structure upon further increase the Fe content to 80%-90%. The substitution of Ni by Fe in the crystals and the dominance of the BCC phase over the FCC structure gave rise to enhanced magnetization. By contrast, the coercive field decreased as a function of increasing Fe because of the reduction in shape anisotropy and the rise of saturation magnetization.

Effect of cobalt on microstructure and properties of AlCr1.5CuFeNi2Cox high-entropy alloys

NASA Astrophysics Data System (ADS)

Kukshal, Vikas; Patnaik, Amar; Bhat, I. K.

2018-04-01

The present paper investigates the effect of Co addition on the alloying behaviour, microstructure and the resulting properties of cast AlCr1.5CuFeNi2Cox high-entropy alloys intended to be used for high temperature applications. The elements Al, Cr, Cu, Fe, Ni and Co (Purity > 99) weighing approximately 800 g was melted in a high temperature vacuum induction furnace. The microstructure, phase transformation, density, microhardness and compressive strength of the samples were analysed using x-ray diffraction (XRD), scanning electron microscopes (SEM), Vickers microhardness tester and universal Testing machine. The crystalline structure of the alloys exhibits simple FCC and BCC phases. The microstructures investigation of the alloys shows the segregation of copper in the interdendritic region resulting in Cu-rich FCC phase. The addition of Co further enhances the formation of FCC phase resulting in the decrease in micro hardness value of the alloys, which varies from 471 HV to 364 HV with increase in the cobalt content from x = 0 to x = 1 (molar ratio). The similar decreasing trend is also observed for the compressive strength of the alloys.

Damage accumulation in ion-irradiated Ni-based concentrated solid-solution alloys

DOE PAGES

Ullah, Mohammad W.; Aidhy, Dilpuneet S.; Zhang, Yanwen; ...

2016-03-05

We investigate Irradiation-induced damage accumulation in Ni 0.8Fe 0.2 and Ni 0.8Cr 0.2 alloys by using molecular dynamics simulations to assess possible enhanced radiation-resistance in these face-centered cubic (fcc), single-phase, concentrated solid-solution alloys, as compared with pure fcc Ni.

In-situ electrochemical-AFM study of localized corrosion of AlxCoCrFeNi high-entropy alloys in chloride solution

NASA Astrophysics Data System (ADS)

Shi, Yunzhu; Collins, Liam; Balke, Nina; Liaw, Peter K.; Yang, Bin

2018-05-01

In-situ electrochemical (EC)-AFM is employed to investigate the localized corrosion of the AlxCoCrFeNi high-entropy alloys (HEAs). Surface topography changes on the micro/sub-micro scale are monitored at different applied anodizing potentials in a 3.5 wt% NaCl solution. The microstructural evolutions with the increased Al content in the alloys are characterized by SEM, TEM, EDS and EBSD. The results show that by increasing the Al content, the microstructure changes from single solid-solution to multi-phases, leading to the segregations of elements. Due to the microstructural variations in the AlxCoCrFeNi HEAs, localized corrosion processes in different ways after the breakdown of the passive film, which changes from pitting to phase boundary corrosion. The XPS results indicate that an increased Al content in the alloys/phases corresponds to a decreased corrosion resistance of the surface passive film.

Cryo-quenched Fe-Ni-Cr alloy single crystals: A new decorative steel

DOE PAGES

Boatner, Lynn A.; Kolopus, James A.; Lavrik, Nicolay V.; ...

2016-08-31

In this paper, a decorative steel is described that is formed by a process that is unlike that of the fabrication methods utilized in making the original Damascus steels over 2000 years ago. The decorative aspect of the steel arises from a three-dimensional surface pattern that results from cryogenically quenching polished austenitic alloy single crystals into the martensitic phase that is present below 190 K. No forging operations are involved – the mechanism is entirely based on the metallurgical phase properties of the ternary alloy. The symmetry of the decorative pattern is determined and controlled by the crystallographic orientation andmore » symmetry of the 70%Fe,15%Ni,15%Cr alloy single crystals. Finally, in addition to using “cuts” made along principal crystallographic surface directions, an effectively infinite number of other random-orientation “cuts” can be utilized to produce decorative patterns where each pattern is unique after the austenitic-to-martensitic phase transformation.« less

Cryogenic strength improvement by utilizing room-temperature deformation twinning in a partially recrystallized VCrMnFeCoNi high-entropy alloy

PubMed Central

Jo, Y. H.; Jung, S.; Choi, W. M.; Sohn, S. S.; Kim, H. S.; Lee, B. J.; Kim, N. J.; Lee, S.

2017-01-01

The excellent cryogenic tensile properties of the CrMnFeCoNi alloy are generally caused by deformation twinning, which is difficult to achieve at room temperature because of insufficient stress for twinning. Here, we induced twinning at room temperature to improve the cryogenic tensile properties of the CrMnFeCoNi alloy. Considering grain size effects on the critical stress for twinning, twins were readily formed in the coarse microstructure by cold rolling without grain refinement by hot rolling. These twins were retained by partial recrystallization and played an important role in improving strength, allowing yield strengths approaching 1 GPa. The persistent elongation up to 46% as well as the tensile strength of 1.3 GPa are attributed to additional twinning in both recrystallized and non-recrystallization regions. Our results demonstrate that non-recrystallized grains, which are generally avoided in conventional alloys because of their deleterious effect on ductility, can be useful in achieving high-strength high-entropy alloys. PMID:28604656

First principles study on Fe based ferromagnetic quaternary Heusler alloys

NASA Astrophysics Data System (ADS)

Amudhavalli, A.; Rajeswarapalanichamy, R.; Iyakutti, K.

2017-11-01

The study of stable half-metallic ferromagnetic materials is important from various fundamental and application points of view in condensed matter Physics. Structural phase stability, electronic structure, mechanical and magnetic properties of Fe-based quaternary Heusler alloys XX‧YZ (X = Co, Ni; X‧ = Fe; Y = Ti; Z = Si, Ge, As) for three different phases namely α, β and γ phases of LiMgPdSn crystal structure have been studied by density functional theory with generalized gradient approximation formulated by Perdew, Burke and Ernzerhof (GGA-PBE) and the Hubbard formalism (GGA-PBE + U). This work aims to identify the ferromagnetic and half-metallic properties of XX‧YZ (X = Co, Ni, X‧ = Fe; Y = Ti; Z = Si, Ge, As) quaternary Heusler alloys. The predicted phase stability shows that α-phase is found to be the lowest energy phase at ambient pressure. A pressure-induced structural phase transition is observed in CoFeTiSi, CoFeTiGe, CoFeTiAs, NiFeTiSi, NiFeTiGe and NiFeTiAs at the pressures of 151.6 GPa, 33.7 GPa, 76.4 GPa, 85.3 GPa, 87.7 GPa and 96.5 GPa respectively. The electronic structure reveals that these materials are half metals at normal pressure whereas metals at high pressure. The investigation of electronic structure and magnetic properties are performed to reveal the underlying mechanism of half metallicity. The spin polarized calculations concede that these quaternary Heusler compounds may exhibit the potential candidate in spintronics application. The magnetic moments for these quaternary Heusler alloys in all the three different phases (α, β and γ) are estimated.

Solidification characteristics and segregation behavior of a P-containing Ni-Fe-Cr-based alloy

NASA Astrophysics Data System (ADS)

Wang, Changshuai; Su, Haijun; Guo, YongAn; Guo, Jianting; Zhou, Lanzhang

2017-09-01

Solidification characteristics and segregation behavior of a P-containing Ni-Fe-Cr-based alloy, considered as boiler and turbine materials in 700 °C advanced ultra-supercritical coal-fired power plants, have been investigated by differential thermal analysis and directional solidification quenching technique. Results reveal that P decreases the solidus temperature, but only has negligible influence on liquidus temperature. After P was added, the solidification sequence has no apparent change, but the width of the mushy zone increases and dendritic structures become coarser. Moreover, P increases the amount and changes the morphology of MC carbide. Energy-dispersive spectroscopy analysis reveals that P has obvious influence on the segregation behavior of the constitute elements with equilibrium partition coefficients (ki) far away from unity, whereas has negligible effect on the constituent elements with ki close to unity and has more influence on the final stage of solidification than at early stage. The distribution profiles reveal that P atoms pile up ahead of the solid/liquid (S/L) interface and strongly segregate to the interdendritic liquid region. The influence of P on solidification characteristics and segregation behavior of Ni-Fe-Cr-based alloy could be attributed to the accumulation of P ahead of the S/L interface during solidification.

Hierachical Ni@Fe2O3 superparticles through epitaxial growth of γ-Fe2O3 nanorods on in situ formed Ni nanoplates

NASA Astrophysics Data System (ADS)

Tahir, Muhammad Nawaz; Herzberger, Jana; Natalio, Filipe; Köhler, Oskar; Branscheid, Robert; Mugnaioli, Enrico; Ksenofontov, Vadim; Panthöfer, Martin; Kolb, Ute; Frey, Holger; Tremel, Wolfgang

2016-05-01

One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water.One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water. Electronic supplementary

Influence of compositional complexity on interdiffusion in Ni-containing concentrated solid-solution alloys

DOE PAGES

Jin, Ke; Zhang, Chuan; Zhang, Fan; ...

2018-03-07

To investigate the compositional effects on thermal-diffusion kinetics in concentrated solid-solution alloys, interdiffusion in seven diffusion couples with alloys from binary to quinary is systematically studied. The alloys with higher compositional complexity exhibit in general lower diffusion coefficients against homologous temperature, however, an exception is found that diffusion in NiCoFeCrPd is faster than in NiCoFeCr and NiCoCr. While the derived diffusion parameters suggest that diffusion in medium and high entropy alloys is overall more retarded than in pure metals and binary alloys, they strongly depend on specific constituents. The comparative features are captured by computational thermodynamics approaches using a self-consistentmore » database.« less

Preparation and Oxidation Performance of Y and Ce-Modified Cr Coating on open-cell Ni-Cr-Fe Alloy Foam by the Pack Cementation

NASA Astrophysics Data System (ADS)

Pang, Q.; Hu, Z. L.; Wu, G. H.

2016-12-01

Metallic foams with a high fraction of porosity, low density and high-energy absorption capacity are a rapidly emerging class of novel ultralight weight materials for various engineering applications. In this study, Y-Cr and Ce-Cr-coated Ni-Cr-Fe alloy foams were prepared via the pack cementation method, and the effects of Y and Ce addition on the coating microstructure and oxidation performance were analyzed in order to improve the oxidation resistance of open-cell nickel-based alloy foams. The results show that the Ce-Cr coating is relatively more uniform and has a denser distribution on the surface of the nickel-based alloy foam. The surface grains of the Ce-Cr-coated alloy foam are finer compared to those of the Y-Cr-coated alloy foam. An obvious Ce peak appears on the interface between the coating and the alloy foam strut, which gives rise to a "site-blocking" effect for the short-circuit transport of the cation in the substrate. X-ray diffraction analysis shows that the Y-Cr-coated alloy foam mainly consists of Cr, (Fe, Ni) and (Ni, Cr) phases in the surface layer. The Ce-Cr-coated alloy foam is mainly composed of Cr and (Ni, Cr) phases. Furthermore, the addition of Y and Ce clearly lead to an improvement in the oxidation resistance of the coated alloy foams in the temperature range of 900-1000 °C. The addition of Ce is especially effective in enhancing the diffusion of chromium to the oxidation front, thus, accelerating the formation of a Cr2O3 layer.

Corrosion study of single crystal Ni-Mn-Ga alloy and Tb0.27Dy0.73Fe1.95 alloy for the design of new medical microdevices.

PubMed

Pouponneau, Pierre; Savadogo, Oumarou; Napporn, Teko; Yahia, L'Hocine; Martel, Sylvain

2011-02-01

Once placed in a magnetic field, smart magnetic materials (SMM) change their shape, which could be use for the development of smaller minimally invasive surgery devices activated by magnetic field. However, the potential degradation and release of cytotoxic ions by SMM corrosion has to be determined. This paper evaluates the corrosion resistance of two SMM: a single crystal Ni-Mn-Ga alloy and Tb(0.27)Dy(0.73)Fe(1.95) alloy. Ni-Mn-Ga alloy displayed a corrosion potential (E (corr)) of -0.58 V/SCE and a corrosion current density (i (corr)) of 0.43 μA/cm(2). During the corrosion assay, Ni-Mn-Ga sample surface was partially protected; local pits were formed on 20% of the surface and nickel ions were mainly found in the electrolyte. Tb(0.27)Dy(0.73)Fe(1.95) alloy exhibited poor corrosion properties such as E (corr) of -0.87 V/SCE and i (corr) of 5.90 μA/cm(2). During the corrosion test, this alloy was continuously degraded, its surface was impaired by pits and cracks extensively and a high amount of iron ions was measured in the electrolyte. These alloys exhibited low corrosion parameters and a selective degradation in the electrolyte. They could only be used for medical applications if they are coated with high strain biocompatible materials or embedded in composites to prevent direct contact with physiological fluids.

N-doped graphene layers encapsulated NiFe alloy nanoparticles derived from MOFs with superior electrochemical performance for oxygen evolution reaction

NASA Astrophysics Data System (ADS)

Feng, Yi; Yu, Xin-Yao; Paik, Ungyu

2016-09-01

Water splitting, an efficient approach for hydrogen production, is often hindered by unfavorable kinetics of oxygen evolution reaction (OER). In order to reduce the overpotential, noble metal oxides-based electrocatalysts like RuO2 and IrO2 are usually utilized. However, due to their scarcity, the development of cost-effective non-precious OER electrocatalysts with high efficiency and good stability is urgently required. Herein, we report a facile one-step annealing of metal-organic frameworks (MOFs) strategy to synthesize N-doped graphene layers encapsulated NiFe alloy nanoparticles (NiFe@C). Through tuning the nanoparticle size and calcination temperature, NiFe@C with an average size of around 16 nm obtained at 700 °C exhibits superior OER performance with an overpotential of only 281 mV at 10 mA cm-2 and high durability. The facile synthesis method and excellent electrochemical performance show great potential of NiFe@C in replacing the precious metal-based electrocatalysts in the OER.

Magnetization of ternary alloys based on Fe0.65Ni0.35 invar with 3d transition metal additions: An ab initio study

NASA Astrophysics Data System (ADS)

Onoue, Masatoshi; Trimarchi, Giancarlo; Freeman, Arthur J.; Popescu, Voicu; Matsen, Marc R.

2015-01-01

Smart susceptors are being developed for use as tooling surfaces in molding machines that use apply electro-magnetic induction heating to mold and form plastics or metal powders into structural parts, e.g., on aerospace and automotive manufacturing lines. The optimal magnetic materials for the induction heating process should have large magnetization, high magnetic permeability, but also small thermal expansion coefficient. The Fe0.65Ni0.35 invar alloy with its negligible thermal expansion coefficient is thus a natural choice for this application. Here, we use density functional theory as implemented through the Korringa-Kohn-Rostoker method within the coherent-potential approximation, to design new alloys with the large magnetization desired for smart susceptor applications. We consider the Fe0.65-xNi0.35-yMx+y alloys derived from Fe0.65Ni0.35 invar adding a third element M = Sc, Ti, V, Cr, Mn, or Co with concentration (x + y) reaching up to 5 at. %. We find that the total magnetization depends linearly on the concentration of M. Specifically, the early 3d transition metals from Sc to Cr decrease the magnetization with respect to that of the invar alloy whereas Mn and Co increase it.

On improving the fracture toughness of a NiAl-based alloy by mechanical alloying

NASA Technical Reports Server (NTRS)

Kostrubanic, J.; Koss, D. A.; Locci, I. E.; Nathal, M.

1991-01-01

Mechanical alloying (MA) has been used to process the NiAl-based alloy Ni-35Al-20Fe, such that a fine-grain (about 2 microns) microstructure is obtained through the addition of 2 vol pct Y2O3 particles. When compared to a conventionally processed, coarse-grained (about 28 microns) Ni-35-20 alloy without the Y2O3 particles, the MA alloy exhibits two to three times higher fracture toughness values, despite a 50-percent increase in yield strength. Room-temperature K(O) values as high as 34 MPa sq rt m are observed, accompanied by a yield strength in excess of 1100 MPa. Fractography confirms a change in fracture characteristics of the fine-grained MA alloy.

Microstructure, hyperfine interaction and magnetic transition of Fe-25%Ni-5%Si-x%Co alloys

NASA Astrophysics Data System (ADS)

Gungunes, H.

2016-12-01

Morphological and magnetic properties in Fe-25%Ni-5%Si-x%Co (x = 0, 10, 15) alloys are investigated. Scanning electron microscopy (SEM), Mössbauer spectroscopy and AC magnetic susceptibility measurements are used to determine the physical properties of alloys. The martensite morphology changed depending on the Co content. The Mössbauer study shows that the volume fraction and hyperfine field of martensite increases while isomer shift values decrease with increasing Co content. On the other hand; AC susceptibility results showed that; Co is an effective element which can be used to control both the magnetic transition and martensitic transformation temperatures.

Effect of d electrons on defect properties in equiatomic NiCoCr and NiCoFeCr concentrated solid solution alloys

DOE PAGES

Zhao, Shijun; Egami, Takeshi; Stocks, G. Malcolm; ...

2018-01-01

Here, the role of d electrons in determining distributions of formation and migration energies for point defects in equiatomic NiCoCr and NiCoFeCr concentrated solid solution alloys (CSAs) are studied regarding electron density deformation flexibility based on first-principles calculations. The disordered state is taken into account by constructing special quasirandom structures. The migration barriers are determined by directly optimizing the saddle point. It is found that the formation energies of interstitials in CSAs are lower than those in pure Ni, whereas the formation energies of vacancies are higher. In both NiCoCr and NiCoFeCr, Co-related dumbbell interstitials exhibit lower formation energies. Notably,more » the distributions of migration energies for Cr interstitials and vacancies exhibit a remarkable overlap region. A detailed analysis of electronic properties reveals that the electronic charge deformation flexibility regarding e g to t 2g transition has a dominant effect on defect energetics for different elements in CSAs. Thus the electron deformation ability is suggested as a key factor in understanding the peculiar defect behavior in CSAs.« less

Effect of d electrons on defect properties in equiatomic NiCoCr and NiCoFeCr concentrated solid solution alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Shijun; Egami, Takeshi; Stocks, G. Malcolm

Here, the role of d electrons in determining distributions of formation and migration energies for point defects in equiatomic NiCoCr and NiCoFeCr concentrated solid solution alloys (CSAs) are studied regarding electron density deformation flexibility based on first-principles calculations. The disordered state is taken into account by constructing special quasirandom structures. The migration barriers are determined by directly optimizing the saddle point. It is found that the formation energies of interstitials in CSAs are lower than those in pure Ni, whereas the formation energies of vacancies are higher. In both NiCoCr and NiCoFeCr, Co-related dumbbell interstitials exhibit lower formation energies. Notably,more » the distributions of migration energies for Cr interstitials and vacancies exhibit a remarkable overlap region. A detailed analysis of electronic properties reveals that the electronic charge deformation flexibility regarding e g to t 2g transition has a dominant effect on defect energetics for different elements in CSAs. Thus the electron deformation ability is suggested as a key factor in understanding the peculiar defect behavior in CSAs.« less

Solid-solution CrCoCuFeNi high-entropy alloy thin films synthesized by sputter deposition

DOE PAGES

An, Zhinan; Jia, Haoling; Wu, Yueying; ...

2015-05-04

The concept of high configurational entropy requires that the high-entropy alloys (HEAs) yield single-phase solid solutions. However, phase separations are quite common in bulk HEAs. A five-element alloy, CrCoCuFeNi, was deposited via radio frequency magnetron sputtering and confirmed to be a single-phase solid solution through the high-energy synchrotron X-ray diffraction, energy-dispersive spectroscopy, wavelength-dispersive spectroscopy, and transmission electron microscopy. The formation of the solid-solution phase is presumed to be due to the high cooling rate of the sputter-deposition process.

Synthesis of FeCoNi nanoparticles by galvanostatic technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budi, Setia, E-mail: setiabudi@unj.ac.id; Department of Chemistry, Faculty of Mathematics and Sciences, Universitas Negeri Jakarta, Jl. Pemuda No.10, Rawamangun, Jakarta 13220; Hafizah, Masayu Elita

Soft magnetic nanoparticles of FeCoNi have been becoming interesting objects for many researchers due to its potential application in electronic devices. One of the most promising methods for material preparation is the electrodeposition which capable of growing nanoparticles alloy directly onto the substrate. In this paper, we report our electrodeposition studies on nanoparticles synthesis using galvanostatic electrodeposition technique. Chemical composition of the synthesized FeCoNi was successfully controlled through the adjustment of the applied currents. It is revealed that the content of each element, obtained from quantitative analysis using atomic absorption spectrometer (AAS), could be modified by the adjustment of currentmore » in which Fe and Co content decreased at larger applied currents, while Ni content increased. The nanoparticles of Co-rich FeCoNi and Ni-rich FeCoNi were obtained from sulphate electrolyte at the range of applied current investigated in this work. Broad diffracted peaks in the X-ray diffractograms indicated typical nanostructures of the solid solution of FeCoNi.« less

Vacancy-mediated fcc/bcc phase separation in Fe 1-xNi x ultrathin films

DOE PAGES

Mentes, T. O.; Stojic, N.; Vescovo, E.; ...

2016-08-01

The phase separation occurring in Fe-Ni thin lms near the Invar composition is studied by using high resolution spectromicroscopy techniques and density functional theory calculations. Annealed at temperatures around 300 C, Fe 0.70Ni 0.30 lms on W(110) break into micron-sized bcc and fcc domains with compositions in agreement with the bulk Fe-Ni phase diagram. Ni is found to be the di using species in forming the chemical heterogeneity. The experimentally-determined energy barrier of 1.59 0.09 eV is identi ed as the vacancy formation energy via density functional theory calculations. Thus, the principal role of the surface in the phase separationmore » process is attributed to vacancy creation without interstitials.« less

Damping studies in Ni-Mn-Ga-Fe/PU polymer composites

NASA Astrophysics Data System (ADS)

Saranya, C.; Kumar, S. Vinodh; Seenithurai, S.; Pandyan, R. Kodi; Munieswaran, P.; Mahendran, M.

2015-06-01

Ni-Mn-Ga-Fe/PU polymer composite is prepared to investigate the damping behavior by using an indigenous experimental setup. The excellent damping properties of Ni-Mn-Ga-Fe alloys bonded with polymer matrix makes possible to develop new damping materials which are effective, less expensive and easier than bulk Ni-Mn-Ga. At low frequency, the stress amplitude increases and then smoothly decreases on increasing the frequency.

High pressure synthesis of a hexagonal close-packed phase of the high-entropy alloy CrMnFeCoNi

DOE PAGES

Tracy, Cameron L.; Park, Sulgiye; Rittman, Dylan R.; ...

2017-05-25

High pressure x-ray diffraction measurements reveal that the face-centered cubic (fcc) high-entropy alloy CrMnFeCoNi transforms martensitically to a hexagonal close-packed (hcp) phase at ~14 GPa. We attribute this to suppression of the local magnetic moments, destabilizing the fcc phase. Similar to fcc-to-hcp transformations in Al and the noble gases, this transformation is sluggish, occurring over a range of >40 GPa. But, the behavior of CrMnFeCoNi is unique in that the hcp phase is retained following decompression to ambient pressure, yielding metastable fcc-hcp mixtures.

Testing the role of metal hydrolysis in the anomalous electrodeposition of Ni-Fe alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, T.M.; St. Clair, J.

1996-12-01

With the objective of testing several models of the anomalous codeposition (ACD) encountered in the electrodeposition of nickel-iron alloys, the effects of bath pH and complexing agents on the composition of deposits were examined. When the pH of the base line bath was increased from 3.0 to 5.0, the Ni/Fe mass ratio of the deposit increased (i.e., the deposition became less anomalous). The presence of tartrate ion in the bath produced a slight decrease in the Ni/Fe of the deposit. This complexing agent complexes ferric ion and thus prevents its precipitation but has little interaction with ferrous ion or nickelmore » ion under the electrodeposition conditions examined. The addition of ethylenediamine to the bath produced a significant increase in the Ni/Fe mass ratio. This complexing agent does not interact significantly with ferric ion or ferrous ion under the test conditions. None of these observations are consistent with the Dahms and Croll model of ACD. The effects of pH and tartaric acid on the deposit composition are consistent with the predictions of the Grande and Talbot model and the Matlosz model. The effect of ethylenediamine is not consistent with the Grande and Talbot model, but may be interpreted within the framework of the Matlosz model and the Hessami and Tobias model.« less

Application of the radioisotope excited X-ray fluorescence technique in charge optimization during thermite smelting of Fe-Ni, Fe-cr, and Fe-Ti alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, I.G.; Joseph, D.; Lal, M.

1995-10-01

A wide range of ferroalloys are used to facilitate the addition of different alloying elements to molten steel. High-carbon ferroalloys are produced on a tonnage basis by carbothermic smelting in an electric furnace, and an aluminothermic route is generally adopted for small scale production of low-carbon varieties. The physicochemical principles of carbothermy and aluminothermy have been well documented in the literature. However, limited technical data are reported on the production of individual ferroalloys of low-carbon varieties from their selected resources. The authors demonstrate her the application of an energy dispersive X-ray fluorescence (EDXRF) technique in meeting the analytical requirements ofmore » a thermite smelting campaign, carried out with the aim of preparing low-carbon-low-nitrogen Fe-Ni, Fe-Cr, and Fe-Ti alloys from indigenously available nickel bearing spent catalyst, mineral chromite, and ilmenite/rutile, respectively. They have chosen the EDXRF technique to meet the analytical requirements because of its capability to analyze samples of ore, minerals, a metal, and alloys in different forms, such as powder, sponge, as-smelted, or as-cast, to obtain rapid multielement analyses with ease. Rapid analyses of thermite feed and product by this technique have aided in the appropriate alterations of the charge constitutents to obtain optimum charge consumption.« less

Local structure study of Fe dopants in Ni-deficit Ni 3Al alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

V. N. Ivanovski; Umicevic, A.; Belosevic-Cavor, J.

2015-08-24

We found that the local electronic and magnetic structure, hyperfine interactions, and phase composition of polycrystalline Ni–deficient Ni 3-x FexAl (x = 0.18 and 0.36) were investigated by means of 57 Fe Mössbauer spectroscopy. The samples were characterized by X–ray diffraction and magnetization measurements. The ab initio calculations performed with the projector augmented wave method and the calculations of the energies of iron point defects were done to elucidate the electronic structure and site preference of Fe doped Ni 3 Al. Moreover, the value of calculated electric field gradient tensor V zz=1.6 10 21Vm -2 matches well with the resultsmore » of Mössbauer spectroscopy and indicates that the Fe atoms occupy Ni sites.« less

Preliminary Microstructural and Microscratch Results of Ni-Cr-Fe and Cr3C2-NiCr Coatings on Magnesium Substrate

NASA Astrophysics Data System (ADS)

Istrate, B.; Munteanu, C.; Lupescu, S.; Benchea, M.; Vizureanu, P.

2017-06-01

Thermal coatings have a large scale application in aerospace and automotive field, as barriers improving wear mechanical characteristics and corrosion resistance. In present research, there have been used two types of coatings, Ni-Cr-Fe, respectively Cr3C2-NiCr which were deposited on magnesium based alloys (pure magnesium and Mg-30Y master alloy). There have been investigated the microstructural aspects through scanning electronic microscopy and XRD analysis and also a series of mechanical characteristics through microscratch and indentation determinations. The results revealed the formation of some adherent layers resistant to the penetration of the metallic indenter, the coatings did not suffer major damages. Microstructural analysis highlighted the formation of Cr3C2, Cr7C3, Cr3Ni2, Cr7Ni3, FeNi3, Cr-Ni phases. Also, the apparent coefficient of friction for Ni-Cr-Fe coatings presents superior values than Cr3C2-NiCr coatings.

Magnetic hysterysis evolution of Ni-Al alloy with Fe and Mn substitution by vacuum arc melting to produce the room temperature magnetocaloric effect material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Notonegoro, Hamdan Akbar; Mechanical Engineering Dept., FT-Universitas Sultan Ageng Tirtayasa, Cilegon 42435; Kurniawan, Budhy

The development of magnetocaloric effect (MCE) material is done in order to reduce the damage of the ozone layer caused by the chlorofluorocarbons (CFCs) emitted into the air. The research dealing with synthesis of magnetocaloric materials based of Ni-Al Heusler Alloy structure and by varying substitution some atoms of Ni with Fe and Al with Mn on Ni-Al Heusler Alloy structure to become Ni{sub 44}Fe{sub 6}Mn{sub 32}Al{sub 18}. Vacuum Arc Melting (VAM) equipment is used to form the alloys on vacuum condition and by flowing argon gas atmosphere and then followed by annealing process for 72 hours. X-Ray Diffraction (XRD)more » reveals that crystallite structure of material is observed. We define that Ni{sub 44}Fe{sub 6} as X{sub 2}, Mn{sub 25} as Y, and Al{sub 18}Mn{sub 7} as Z. Based on the XRD result, we observed that the general formula X{sub 2}YZ is not changed. The PERMAGRAF measurement revealed that there exists of magnetic hysterysis. The hysterysis show that the magnetic structures of the system undego evolution from diamagnetic to soft ferromagnetic material which all of the compound have the same crystallite structure. This evolution indicated that the change in the composition has led to changes the magnetic composition. Mn is the major element that gives strong magnetic properties to the sample. When Mn partially replaced position of Al, the sample became dominant to be influenced to improve their magnetic properties. In addition, substitution a part of Ni by Fe in the composition reveals a pinning of the domain walls in the sample.« less

Characterization of Cu buffer layers for growth of L10-FeNi thin films

NASA Astrophysics Data System (ADS)

Mizuguchi, M.; Sekiya, S.; Takanashi, K.

2010-05-01

A Cu(001) layer was fabricated on a Au(001) layer to investigate the use of Cu as a buffer layer for growing L10-FeNi thin films. The epitaxial growth of a Cu buffer layer was observed using reflection high-energy electron diffraction. The flatness of the layer improved drastically with an increase in the substrate temperature although the layer was an alloy (AuCu3). An FeNi thin film was epitaxially grown on the AuCu3 buffer layer by alternate monatomic layer deposition and the formation of an L10-FeNi ordered alloy was expected. The AuCu3 buffer layer is thus a promising candidate material for the growth of L10-FeNi thin films.

Effect of cold rolling on the microstructure and mechanical properties of Al 0.25CoCrFe 1.25Ni 1.25 high-entropy alloy

DOE PAGES

Wang, Z.; Gao, M. C.; Ma, S. G.; ...

2015-08-05

Cold rolling can break down the as-cast dendrite microstructure and thus may have pronounced impact on the mechanical behavior of the alloy. In the present study, the effect of cold rolling on the microstructure and mechanical properties of Al 0.25CoCrFe 1.25Ni 1.25 high-entropy alloy in the face-centered cubic structure was investigated. With increasing the thickness reduction from cold rolling, the hardness, the yield strength, and the fracture strength increased at the cost of reducing ductility. At the thickness reduction of 80%, the tensile strength (hardness) was 702 MPa (406 MPa), 1.62 (2.43) times that in the as-cast condition. Compared tomore » traditional alloys, Al 0.25CoCrFe 1.25Ni 1.25 has the highest hardening rate with respect to CR thickness reduction. Lastly, the phase relation and the mixing properties of Gibbs free energy, enthalpy and entropy of Al xCoCrFe 1.25Ni 1.25 were predicted using the CALPHAD method.« less

The BCC/B2 morphologies in Al xNiCoFeCr high-entropy alloys

DOE PAGES

Ma, Yue; Jiang, Beibei; Li, Chunling; ...

2017-02-15

Here, the present work primarily investigates the morphological evolution of the body-centered-cubic (BCC)/B2 phases in Al xNiCoFeCr high-entropy alloys (HEAs) with increasing Al content. It is found that the BCC/B2 coherent morphology is closely related to the lattice misfit between these two phases, which is sensitive to Al. There are two types of microscopic BCC/B2 morphologies in this HEA series: one is the weave-like morphology induced by the spinodal decomposition, and the other is the microstructure of a spherical disordered BCC precipitation on the ordered B2 matrix that appears in HEAs with a much higher Al content. The mechanical properties,more » including the compressive yielding strength and microhardness of the Al xNiCoFeCr HEAs, are also discussed in light of the concept of the valence electron concentration (VEC).« less

A Successful Synthesis of the CoCrFeNiAl0.3 Single-Crystal, High-Entropy Alloy by Bridgman Solidification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, S. G.; Zhang, S. F.; Gao, M. C.

2013-08-22

For the first time, a face-centered-cubic, single-crystal CoCrFeNiAl{sub 0.3} (designated as Al0.3), high-entropy alloy (HEA) was successfully synthesized by the Bridgman solidification (BS) method, at an extremely low withdrawal velocity through a constant temperature gradient, for which it underwent two BS steps. Specially, at the first BS step, the alloy sample underwent several morphological transitions accompanying the crystal growth from the melt. This microstructure evolves from as-cast dendrites, to equiaxed grains, and then to columnar crystals, and last to the single crystal. In particular, at the equiaxed-grain region, some visible annealing twins were observed, which indicates a low stacking faultmore » energy of the Al0.3 alloy. Although a body-centered- cubic CoCrFeNiAl (Al1) HEA was also prepared under the same conditions, only a single columnar-crystal structure with instinctively preferential crystallographic orientations was obtained by the same procedure. A similar morphological transition from dendrites to equiaxed grains occurred at the equiaxed-grain region in Al1 alloy, but the annealing twins were not observed probably because a higher Al addition leads to a higher stacking fault energy for this alloy.« less

N-doped graphene layers encapsulated NiFe alloy nanoparticles derived from MOFs with superior electrochemical performance for oxygen evolution reaction

PubMed Central

Feng, Yi; Yu, Xin-Yao; Paik, Ungyu

2016-01-01

Water splitting, an efficient approach for hydrogen production, is often hindered by unfavorable kinetics of oxygen evolution reaction (OER). In order to reduce the overpotential, noble metal oxides-based electrocatalysts like RuO2 and IrO2 are usually utilized. However, due to their scarcity, the development of cost-effective non-precious OER electrocatalysts with high efficiency and good stability is urgently required. Herein, we report a facile one-step annealing of metal-organic frameworks (MOFs) strategy to synthesize N-doped graphene layers encapsulated NiFe alloy nanoparticles (NiFe@C). Through tuning the nanoparticle size and calcination temperature, NiFe@C with an average size of around 16 nm obtained at 700 °C exhibits superior OER performance with an overpotential of only 281 mV at 10 mA cm−2 and high durability. The facile synthesis method and excellent electrochemical performance show great potential of NiFe@C in replacing the precious metal-based electrocatalysts in the OER. PMID:27658968

Shape-Memory Effect and Pseudoelasticity in Fe-Mn-Based Alloys

NASA Astrophysics Data System (ADS)

La Roca, P.; Baruj, A.; Sade, M.

2017-03-01

Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe-Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe-Mn-Al-Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc-hcp in the first case and the bcc-fcc in the latter are discussed. Selected potential applications are also analyzed.

Effects of compositional complexity on the ion-irradiation induced swelling and hardening in Ni-containing equiatomic alloys

DOE PAGES

Jin, K.; Lu, C.; Wang, L. M.; ...

2016-04-14

The impact of compositional complexity on the ion-irradiation induced swelling and hardening is studied in Ni and six Ni-containing equiatomic alloys with face-centered cubic structure. The irradiation resistance at the temperature of 500 °C is improved by controlling the number and, especially, the type of alloying elements. Alloying with Fe and Mn has a stronger influence on swelling reduction than does alloying with Co and Cr. Lastly, the quinary alloy NiCoFeCrMn, with known excellent mechanical properties, has shown 40 times higher swelling tolerance than nickel.

Effects of temperature on the irradiation responses of Al 0.1 CoCrFeNi high entropy alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Tengfei; Xia, Songqin; Guo, Wei

Structural damage and chemical segregation in Al 0.1CoCrFeNi high entropy alloy irradiated at elevated temperatures are studied using transmission electron microscopy (TEM) and atom probe tomography (APT). Irradiation-induced defects include dislocation loops, long dislocations and stacking-fault tetrahedra, but no voids can be observed. Furthermore, as irradiation temperature increases, defect density is decreased but defect size is increased, which is induced by increasing defect mobility. Finally, APT characterization reveals that ion irradiation at elevated temperatures can induce an enrichment of Ni and Co as well as a depletion of Fe and Cr at defect clusters, mainly including dislocation loops and longmore » dislocations.« less

Effects of temperature on the irradiation responses of Al 0.1 CoCrFeNi high entropy alloy

DOE PAGES

Yang, Tengfei; Xia, Songqin; Guo, Wei; ...

2017-09-29

Structural damage and chemical segregation in Al 0.1CoCrFeNi high entropy alloy irradiated at elevated temperatures are studied using transmission electron microscopy (TEM) and atom probe tomography (APT). Irradiation-induced defects include dislocation loops, long dislocations and stacking-fault tetrahedra, but no voids can be observed. Furthermore, as irradiation temperature increases, defect density is decreased but defect size is increased, which is induced by increasing defect mobility. Finally, APT characterization reveals that ion irradiation at elevated temperatures can induce an enrichment of Ni and Co as well as a depletion of Fe and Cr at defect clusters, mainly including dislocation loops and longmore » dislocations.« less

Vacuum Brazing TC4 Titanium Alloy to 304 Stainless Steel with Cu-Ti-Ni-Zr-V Amorphous Alloy Foil

NASA Astrophysics Data System (ADS)

Dong, Honggang; Yang, Zhonglin; Wang, Zengrui; Deng, Dewei; Dong, Chuang

2014-10-01

Dissimilar metal vacuum brazing between TC4 titanium alloy and 304 stainless steel was conducted with newly designed Cu-Ti-Ni-Zr-V amorphous alloy foils as filler metals. Solid joints were obtained due to excellent compatibility between the filler metal and stainless steel substrate. Partial dissolution of stainless steel substrate occurred during brazing. The shear strength of the joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25 foil was 105 MPa and that with Cu37.5Ti25Ni12.5Zr12.5V12.5 was 116 MPa. All the joints fractured through the gray layer in the brazed seam, revealing brittle fracture features. Cr4Ti, Cu0.8FeTi, Fe8TiZr3 and Al2NiTi3C compounds were found in the fractured joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25 foil, and Fe2Ti, TiCu, Fe8TiZr3 and NiTi0.8Zr0.3 compounds were detected in the joint brazed with Cu37.5Ti25Ni12.5Zr12.5V12.5 foil. The existence of Cr-Ti, Fe-Ti, Cu-Fe-Ti, and Fe-Ti-V intermetallic compounds in the brazed seam caused fracture of the resultant joints.

Site preference of ternary alloying additions to NiTi: Fe, Pt, Pd, Au, Al, Cu, Zr and Hf

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Noebe, Ronald D.; Mosca, Hugo O.

2004-01-01

Atomistic modeling of the site substitution behavior of Pd in NiTi (J. Alloys and Comp. (2004), in press) has been extended to examine the behavior of several other alloying additions, namely, Fe, Pt, Au, Al, Cu, Zr and Hf in this important shape memory alloy. It was found that all elements, to a varying degree, displayed absolute preference for available sites in the deficient sublattice. How- ever, the energetics of the different substitutional schemes, coupled with large scale simulations indicate that the general trend in all cases is for the ternary addition to want to form stronger ordered structures with Ti.

Study of reversible magnetization in FeCoNi alloy nanowires with different diameters by first order reversal curve (FORC) diagrams

NASA Astrophysics Data System (ADS)

Samanifar, S.; Kashi, M. Almasi; Ramazani, A.

2018-05-01

Magnetic nanowires electrodeposited into solid templates are of high interest due to their tunable properties which are required for magnetic recording media and spintronic devices. Here, highly ordered arrays of FeCoNi NWs with varied diameters (between 60 and 150 nm) were fabricated into nanopores of hard-anodized aluminum oxide templates using pulsed ac electrodeposition technique. X-ray diffraction patterns indicated the formation of FeCoNi NWs with fcc FeNi and bcc FeCo alloy phases, being highly textured along the bcc [110] direction. Magnetic properties were studied by hysteresis loop measurements at room temperature and they showed reductions in coercivity and squareness values by increasing diameter. First-order reversal curve measurements revealed that, with increasing diameter from 60 to 150 nm, besides a transition from a single domain (SD) state to a pseudo SD state, an increase in the reversible magnetization component of the NWs from 11% to 24% occurred.

The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

DOE PAGES

Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir; ...

2017-07-25

Here, Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe 100–xNi x) 80Nb 4Si 2B 14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in allmore » alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe 30Ni 70) 80Nb 4Si 2B 14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr 23C 6-type structure and a likely composition of Fe 21Nb 2B 6. Toroidal losses have been measured for (Fe 70Ni 30) 80Nb 4Si y B 16–y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W 1.0T, 400 Hz = 0.9 W/kg and W 1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.« less

The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir

Here, Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe 100–xNi x) 80Nb 4Si 2B 14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in allmore » alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe 30Ni 70) 80Nb 4Si 2B 14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr 23C 6-type structure and a likely composition of Fe 21Nb 2B 6. Toroidal losses have been measured for (Fe 70Ni 30) 80Nb 4Si y B 16–y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W 1.0T, 400 Hz = 0.9 W/kg and W 1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.« less

The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

NASA Astrophysics Data System (ADS)

Aronhime, Natan; DeGeorge, Vincent; Keylin, Vladimir; Ohodnicki, Paul; McHenry, Michael E.

2017-11-01

Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe100- x Ni x )80Nb4Si2B14 (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in all alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe30Ni70)80Nb4Si2B14 also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr23C6-type structure and a likely composition of Fe21Nb2B6. Toroidal losses have been measured for (Fe70Ni30)80Nb4Si y B16- y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W1.0T, 400 Hz = 0.9 W/kg and W1.0T, 1 kHz = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.

A study of the properties and microstructure of Ni 81Fe 19 ultrathin films with MgO

NASA Astrophysics Data System (ADS)

Li, Minghua; Han, Gan; Ding, Lei; Wang, Xiaocui; Liu, Yang; Feng, Chun; Wang, Haicheng; Yu, Guanghua

2012-01-01

The anisotropic magnetoresistance (AMR) of a Ta (5 nm)/MgO (3 nm)/Ni81Fe19 (10 nm)/MgO (2 nm)/Ta (3 nm) film with MgO-Nano Oxide Layer (NOL) increases dramatically from 1.05% to 3.24% compared with a Ta (5 nm)/Ni81Fe19 (10 nm)/Ta (3 nm) film without the MgO-NOL layer after annealing at 380 °C for 2 h. Although the MgO destroys the NiFe (1 1 1) texture, it enhances the specular electron scattering of the conduction electrons at the NOL interface and suppresses the interface reactions and diffusion at the Ta/NiFe and NiFe/Ta interfaces. The NiFe (1 1 1) texture was formed after the annealing, resulting in a higher AMR ratio. X-ray photoelectron spectroscope results show that Mg and Mg2+ were present in the MgOx films.

Evolution of ion damage at 773K in Ni- containing concentrated solid-solution alloys

DOE PAGES

Shi, Shi; He, Mo-Rigen; Jin, Ke; ...

2018-01-10

Quantitative analysis of the impact of the compositional complexity in a series of Ni-containing concentrated solid-solution alloys, Ni, NiCo, NiFe, NiCoCr, NiCoFeCr, NiCoFeCrMn and NiCoFeCrPd, on the evolution of defects produced by 1 MeV Kr ion irradiation at 773 K is reported in this paper. The dynamics of the evolution of the damage structure during irradiation to a dose of 2 displacements per atom were observed directly by performing the ion irradiations in electron transparent foils in a transmission electron microscope coupled to an ion accelerator. The defect evolution was assessed through measurement of the defect density, defect size andmore » fraction of perfect and Frank loops. These three parameters were dependent on the alloying element as well as the number of elements. The population of loops was sensitive to the ion dose and alloy composition as faulted Frank loops were observed to unfault to perfect loops with increasing ion dose. Finally, these dependences are explained in terms of the influence of each element on the lifetime of the displacement cascade as well as on defect formation and migration energies.« less

Evolution of ion damage at 773K in Ni- containing concentrated solid-solution alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Shi; He, Mo-Rigen; Jin, Ke

Quantitative analysis of the impact of the compositional complexity in a series of Ni-containing concentrated solid-solution alloys, Ni, NiCo, NiFe, NiCoCr, NiCoFeCr, NiCoFeCrMn and NiCoFeCrPd, on the evolution of defects produced by 1 MeV Kr ion irradiation at 773 K is reported in this paper. The dynamics of the evolution of the damage structure during irradiation to a dose of 2 displacements per atom were observed directly by performing the ion irradiations in electron transparent foils in a transmission electron microscope coupled to an ion accelerator. The defect evolution was assessed through measurement of the defect density, defect size andmore » fraction of perfect and Frank loops. These three parameters were dependent on the alloying element as well as the number of elements. The population of loops was sensitive to the ion dose and alloy composition as faulted Frank loops were observed to unfault to perfect loops with increasing ion dose. Finally, these dependences are explained in terms of the influence of each element on the lifetime of the displacement cascade as well as on defect formation and migration energies.« less

Abiotic ammonium formation in the presence of Ni-Fe metals and alloys and its implications for the Hadean nitrogen cycle

PubMed Central

Smirnov, Alexander; Hausner, Douglas; Laffers, Richard; Strongin, Daniel R; Schoonen, Martin AA

2008-01-01

Experiments with dinitrogen-, nitrite-, nitrate-containing solutions were conducted without headspace in Ti reactors (200°C), borosilicate septum bottles (70°C) and HDPE tubes (22°C) in the presence of Fe and Ni metal, awaruite (Ni80Fe20) and tetrataenite (Ni50Fe50). In general, metals used in this investigation were more reactive than alloys toward all investigated nitrogen species. Nitrite and nitrate were converted to ammonium more rapidly than dinitrogen, and the reduction process had a strong temperature dependence. We concluded from our experimental observations that Hadean submarine hydrothermal systems could have supplied significant quantities of ammonium for reactions that are generally associated with prebiotic synthesis, especially in localized environments. Several natural meteorites (octahedrites) were found to contain up to 22 ppm Ntot. While the oxidation state of N in the octahedrites was not determined, XPS analysis of metals and alloys used in the study shows that N is likely present as nitride (N3-). This observation may have implications toward the Hadean environment, since, terrestrial (e.g., oceanic) ammonium production may have been supplemented by reduced nitrogen delivered by metal-rich meteorites. This notion is based on the fact that nitrogen dissolves into metallic melts. PMID:18489746

Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system

NASA Technical Reports Server (NTRS)

Blum, Joel D.; Wasserburg, G. J.; Hutcheon, I. D.; Beckett, J. R.; Stolper, E. M.

1989-01-01

Results are presented on thin-film diffusion experiments designed to investigate phase equilibria in systems containing high concentrations of Pt-group elements, such as Ni-Fe-Ru-rich systems containing Pt, at temperatures of 1273, 1073, and 873 K. The rate of Ru diffusion in Ni was determined as a function of temperature, and, in addition, the degree of Pt and Ir partitioning between phases in a Ni-Fe-Ru-rich system and of V between phases in a Ni-Fe-O-rich system at 873 were determined. It was found that Pt preferentially partitions into the (gamma)Ni-Fe phase, whereas Ir prefers the (epsilon)Ru-Fe phase. V partitions strongly into Fe oxides relative to (gamma)Ni-Fe. These results have direct application to the origin and thermal history of the alloys rich in Pt-group elements in meteorites.

Preparation of metastable CoFeNi alloys with ultra-high magnetic saturation (Bs = 2.4-2.59 T) by reverse pulse electrodeposition

NASA Astrophysics Data System (ADS)

Tabakovic, Ibro; Venkatasamy, Venkatram

2018-04-01

The results of reverse pulse electrodeposition of CoFeNi films with ultra-high magnetic saturation, i.e. Bs values between 2.4 and 2.59 T, are presented in this work. Based on valence-bond theory (Hund's rule) it was assumed that the electronic configuration of MOH obtained by one electron reduction of electroactive intermediate (MOH+ads + e → MOHads) or oxidation of metal (M - e + HOH → MOH + H+) would result with larger number of spins per atom for each of transition metals in MOH-precipitated in CoFeNi deposit- with one more spin than their respective neutral metal in the order: Fe > Co > Ni. The experimental results showed that the increase of Bs value above Slater-Pauling curve was not observed for CoFe alloys, thus FeOH and CoOH compounds were not present in deposit. However, the increase of the Bs values above the Slater-Pauling curve (Bs = 2.4-2.59 T) was observed, for CoFeNi films obtained by reverse pulse electrodeposition. Therefore, NiOH as a stable compound is probably formed in a one-electron oxidation step during anodic pulse oxidation reaction precipitated presumably at the grain boundaries, giving rise to the ultra-high magnetic saturation of CoFeNi films. The effects of experimental conditions on elemental composition, magnetic properties, crystal structure, and thermal stability of CoFeNi films were studied.

Stability of Fe-Ni hydride after the reaction between Fe-Ni alloy and hydrous phase (δ-AlOOH) up to 1.2 Mbar: Possibility of H contribution to the core density deficit

NASA Astrophysics Data System (ADS)

Terasaki, Hidenori; Ohtani, Eiji; Sakai, Takeshi; Kamada, Seiji; Asanuma, Hidetoshi; Shibazaki, Yuki; Hirao, Naohisa; Sata, Nagayoshi; Ohishi, Yasuo; Sakamaki, Tatsuya; Suzuki, Akio; Funakoshi, Ken-ichi

2012-03-01

The hydrous mineral, δ-AlOOH, is stable up to at least the core-mantle boundary, and therefore has been proposed as a water carrier to the Earth's deep mantle. If δ-AlOOH is transported down to the core-mantle boundary by a subducting slab or the mantle convection, then the reaction between the iron alloy core and δ-AlOOH is important in the deep water/hydrogen cycle in the Earth. Here we conducted an in situ X-ray diffraction study to determine the behavior of hydrogen between Fe-Ni alloys and δ-AlOOH up to near the core-mantle boundary conditions. The obtained diffraction spectra show that fcc/dhcp Fe-Ni hydride is stable over a wide pressure range of 19-121 GPa at high temperatures. Although the temperature of formation of Fe-Ni hydride tends to increase up to 1950 K with increasing pressure to 121 GPa, this reaction temperature is well below the mantle geotherm. δ-AlOOH was confirmed to coexist stably with perovskite, suggesting that δ-AlOOH can be a major hydrous phase in the lower mantle. Therefore, when δ-AlOOH contacts with the core at the core-mantle boundary, the hydrogen is likely to dissolve into the Earth's core. Based on the present results, the amount of hydrogen to explain the core density deficit is estimated to be 1.0-2.0 wt.%.

Effect of Cooling Rates on γ → α Transformation and Metastable States in Fe-Cu Alloys with Addition of Ni

NASA Astrophysics Data System (ADS)

Crozet, C.; Verdier, M.; Lay, S.; Antoni-Zdziobek, A.

2018-07-01

α/γ phase transformations occurring in Fe-10Cu-xNi alloys (0 ≤ x ≤ 15 in mass%) were studied using X-ray diffraction, scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy and chemical analysis, combining X-ray microanalysis with energy dispersive spectrometry in the scanning electron microscope and electron microprobe analysis with wavelength dispersive spectrometry. The influence of cooling rate on the microstructure was investigated using ice-brine quenching and 2 °C/min slow cooling rate performed with dilatometry. Ni addition induces metastable transformations on cooling: massive and bainitic ferrite are formed depending on the alloy composition and cooling rate. Moreover, most of the Cu phase precipitates on cooling giving rise to a fine distribution of Cu particles in the ferrite grains. For both cooling conditions, the hardness increases with increasing Ni content and a higher hardness is obtained in the quenched alloy for each composition. The change in hardness is correlated to the effect of Ni solid solution, transformation structure and size of Cu particles.

Thermal expansion in FeCrCoNiGa high-entropy alloy from theory and experiment

NASA Astrophysics Data System (ADS)

Huang, Shuo; Vida, Ádám; Li, Wei; Molnár, Dávid; Kyun Kwon, Se; Holmström, Erik; Varga, Béla; Károly Varga, Lajos; Vitos, Levente

2017-06-01

First-principle alloy theory and key experimental techniques are applied to determine the thermal expansion of FeCrCoNiGa high-entropy alloy. The magnetic transition, observed at 649 K, is accompanied by a significant increase in the thermal expansion coefficient. The phase stability is analyzed as a function of temperature via the calculated free energies accounting for the structural, magnetic, electronic, vibrational and configurational contributions. The single- and polycrystal elastic modulus for the ferro- and paramagnetic states of the face-centered and body-centered cubic phases are presented. By combining the measured and theoretically predicted temperature-dependent lattice parameters, we reveal the structural and magnetic origin of the observed anomalous thermal expansion behavior.

Biased Target Ion Beam Deposition and Nanoskiving for Fabricating NiTi Alloy Nanowires

NASA Astrophysics Data System (ADS)

Hou, Huilong; Horn, Mark W.; Hamilton, Reginald F.

2016-12-01

Nanoskiving is a novel nanofabrication technique to produce shape memory alloy nanowires. Our previous work was the first to successfully fabricate NiTi alloy nanowires using the top-down approach, which leverages thin film technology and ultramicrotomy for ultra-thin sectioning. For this work, we utilized biased target ion beam deposition technology to fabricate nanoscale (i.e., sub-micrometer) NiTi alloy thin films. In contrast to our previous work, rapid thermal annealing was employed for heat treatment, and the B2 austenite to R-phase martensitic transformation was confirmed using stress-temperature and diffraction measurements. The ultramicrotome was programmable and facilitated sectioning the films to produce nanowires with thickness-to-width ratios ranging from 4:1 to 16:1. Energy dispersive X-ray spectroscopy analysis confirmed the elemental Ni and Ti make-up of the wires. The findings exposed the nanowires exhibited a natural ribbon-like curvature, which depended on the thickness-to-width ratio. The results demonstrate nanoskiving is a potential nanofabrication technique for producing NiTi alloy nanowires that are continuous with an unprecedented length on the order of hundreds of micrometers.

Design of Novel Precipitate-Strengthened Al-Co-Cr-Fe-Nb-Ni High-Entropy Superalloys

NASA Astrophysics Data System (ADS)

Antonov, Stoichko; Detrois, Martin; Tin, Sammy

2018-01-01

A series of non-equiatomic Al-Co-Cr-Fe-Nb-Ni high-entropy alloys, with varying levels of Co, Nb and Fe, were investigated in an effort to obtain microstructures similar to conventional Ni-based superalloys. Elevated levels of Co were observed to significantly decrease the solvus temperature of the γ' precipitates. Both Nb and Co in excessive concentrations promoted the formation of Laves and NiAl phases that formed either during solidification and remained undissolved during homogenization or upon high-temperature aging. Lowering the content of Nb, Co, or Fe prevented the formation of the eutectic type Laves. In addition, lowering the Co content resulted in a higher number density and volume fraction of the γ' precipitates, while increasing the Fe content led to the destabilization of the γ' precipitates. Various aging treatments were performed which led to different size distributions of the strengthening phase. Results from the microstructural characterization and hardness property assessments of these high-entropy alloys were compared to a commercial, high-strength Ni-based superalloy RR1000. Potentially, precipitation-strengthened high-entropy alloys could find applications replacing Ni-based superalloys as structural materials in power generation applications.

Microstructural stability and mechanical behavior of FeNiMnCr high entropy alloy under ion irradiation

DOE PAGES

Leonard, Keith J.; Bei, Hongbin; Zinkle, Steven J.; ...

2016-05-13

In recent years, high entropy alloys (HEAs) have attracted significant attention due to their excellent mechanical properties and good corrosion resistance, making them potential candidates for high temperature fission and fusion structural applications. However there is very little known about their radiation resistance, particularly at elevated temperatures relevant for energy applications. In the present study, a single phase (face centered cubic) concentrated solid solution alloy of composition 27%Fe-28%Ni-27%Mn-18%Cr was irradiated with 3 or 5.8 MeV Ni ions at temperatures ranging from room temperature to 700 °C and midrange doses from 0.03 to 10 displacements per atom (dpa). Transmission electron microscopymore » (TEM), scanning transmission electron microscopy with energy dispersive x-ray spectrometry (STEM/EDS) and X-ray diffraction (XRD) were used to characterize the radiation defects and microstructural changes. Irradiation at higher temperatures showed evidence of relatively sluggish solute diffusion with limited solute depletion or enrichment at grain boundaries. The main microstructural feature at all temperatures was high-density small dislocation loops. Voids were not observed at any irradiation condition. Nano-indentation tests on specimens irradiated at room temperature showed a rapid increase in hardness ~35% and ~80% higher than the unirradiated value at 0.03 and 0.3 dpa midrange doses, respectively. The irradiation-induced hardening was less pronounced for 500 °C irradiations (<20% increase after 3 dpa). Overall, the examined HEA material exhibits superior radiation resistance compared to conventional single phase Fe-Cr-Ni austenitic alloys such as stainless steels. Furthermore, the present study provides insight on the fundamental irradiation behavior of a single phase HEA material over a broad range of irradiation temperatures.« less

Evolution of phase transformation and magnetic properties with Fe content in Ni55-x Fe x Mn20Ga25 Heusler alloys

NASA Astrophysics Data System (ADS)

Zhang, Yuanlei; Li, Zhe; He, Xijia; Huang, Yinsheng; Xu, Kun; Jing, Chao

2018-02-01

A series of Ni55-x Fe x Mn20Ga25 (0  ⩽  x  ⩽  5) Heusler alloys was prepared to investigate their phase transitions and magnetic properties. At room temperature, these alloys present various crystal structures, and the unit cell volume enlarges with increase of Fe content in both austenite and martensite. Multiple magneto-structural transformations were observed in the parent alloy (x  =  0). In the process of cooling, it undergoes martensitic transformation (MT) from L21-type paramagnetic austenite to L10-type ferromagnetic martensite, accompanying an intermartensitic transformation (IMT, 7M  →  L10). By establishing a detailed phase diagram, we found that both MT and IMT shift to lower temperature simultaneously, while the ferromagnetic (FM) transition of austenite moves to higher temperature as Fe increases. With the further increase of Fe content beyond a critical value, both the IMT and the FM transitions split off from MT, and the former follows with the transforming sequence of 7M  →  5M. Based on the experimental data, some key magnetic parameters have been obtained in this system. The calculated magnetocrystalline anisotropy constant ({{K}1} ) of martensite quickly increases as Fe increases, and then it almost reaches a saturated value (~5.5  ×  105 J m-3) for the alloys with x  >  3. However, the spontaneous magnetic moment ({μs} ) attains a peak value of about 4.2 μ B/f.u. in the alloy with x  =  4, which is not consistent with the linear increasing of effective magnetic moment ({μef f} ). Further magnetic measurements with hydrostatic pressure indicate that such a discrepancy could be ascribed to the competition between the magnetic exchange interaction and the volume change of unit cell governed by the dopant Fe content.

Coercivity and nanostructure of melt-spun Ti-Fe-Co-B-based alloys

DOE PAGES

Zhang, W. Y.; Skomski, R.; Kashyap, A.; ...

2016-02-18

Nanocrystalline Ti-Fe-Co-B-based alloys, prepared by melt spinning and subsequent annealing, have been characterized structurally and magnetically. X-ray diffraction and thermomagnetic measurements show that the ribbons consist of tetragonal Ti 3(Fe,Co) 5B 2, FeCo-rich bcc, and NiAl-rich L2 1 phases; Ti 3(Fe,Co) 5B 2, is a new substitutional alloy series whose end members Ti 3Co 5B 2 and Ti 3Fe 5B 2 have never been investigated magnetically and may not even exist, respectively. Two compositions are considered, namely Ti 11+xFe 37.5-0.5xCo 37.5–0.5xB 14 (x = 0, 4) and alnico-like Ti 11Fe 26Co 26Ni 10Al 11Cu 2B 14, the latter also containingmore » an L2 1-type alloy. The volume fraction of the Ti 3(Fe,Co) 5B 2 phase increases with x, which leads to a coercivity increase from 221 Oe for x = 0 to 452 Oe for x = 4. Since the grains are nearly equiaxed, there is little or no shape anisotropy, and the coercivity is largely due to the magnetocrystallineanisotropy of the tetragonal Ti 3(Fe,Co) 5B 2 phase. The alloy containing Ni,Al, and Cu exhibits a magnetization of 10.6 kG and a remanence ratio of 0.59. Lastly, our results indicate that magnetocrystallineanisotropy can be introduced in alnico-like magnets, adding to shape anisotropy that may be induced by field annealing.« less

10 000-hr Cyclic Oxidation Behavior of 68 High-Temperature Co-, Fe-, and Ni- Base Alloys Evaluated at 982 deg. C (1800 deg. F)

NASA Technical Reports Server (NTRS)

Barrett, Charles A.

1999-01-01

Power systems with operating temperatures in the range of 815 to 982 C (1500 to 1800 F) frequently require alloys that can operate for long times at these temperatures. A critical requirement is that these alloys have adequate oxidation resistance. The alloys used in these power systems require thousands of hours of operating life with intermittent shutdown to room temperature. Intermittent power plant shutdowns, however, offer the possibility that the protective scale will tend to spall (i.e., crack and flake off) upon cooling, increasing the rate of oxidative attack in subsequent heating cycles. Thus, it is critical that candidate alloys be evaluated for cyclic oxidation behavior. It was determined that exposing test alloys to ten 1000-hr cycles in static air at 982 10 000-hr Cyclic Oxidation Behavior of 68 High-Temperature Co-, Fe-, and Ni-Base Alloys Evaluated at 982 C (1800 F) could give a reasonable simulation of long-time power plant operation. Iron- (Fe-), nickel- (Ni-), and cobalt- (Co-) based high-temperature alloys with sufficient chromium (Cr) and/or aluminum (Al) content can exhibit excellent oxidation resistance. The protective oxides formed by these classes of alloys are typically Cr2O3 and/or Al2O3, and are usually influenced by their Cr, or Cr and Al, content. Sixty-eight Co-, Fe-, and Ni-base high-temperature alloys, typical of those used at this temperature or higher, were used in this study. At the NASA Lewis Research Center, the alloys were tested and compared on the basis of their weight change as a function of time, x-ray diffraction of the protective scale composition, and the physical appearance of the exposed samples. Although final appearance and x-ray diffraction of the final scale products were two factors used to evaluate the oxidation resistance of each alloy, the main criterion was the oxidation kinetics inferred from the specific weight change versus time data. These data indicated a range of oxidation behavior including parabolic

Electrical resistivity of substitutionally disordered hcp Fe-Si and Fe-Ni alloys: Chemically-induced resistivity saturation in the Earth's core

NASA Astrophysics Data System (ADS)

Gomi, Hitoshi; Hirose, Kei; Akai, Hisazumi; Fei, Yingwei

2016-10-01

The thermal conductivity of the Earth's core can be estimated from its electrical resistivity via the Wiedemann-Franz law. However, previously reported resistivity values are rather scattered, mainly due to the lack of knowledge with regard to resistivity saturation (violations of the Bloch-Grüneisen law and the Matthiessen's rule). Here we conducted high-pressure experiments and first-principles calculations in order to clarify the relationship between the resistivity saturation and the impurity resistivity of substitutional silicon in hexagonal-close-packed (hcp) iron. We measured the electrical resistivity of Fe-Si alloys (iron with 1, 2, 4, 6.5, and 9 wt.% silicon) using four-terminal method in a diamond-anvil cell up to 90 GPa at 300 K. We also computed the electronic band structure of substitutionally disordered hcp Fe-Si and Fe-Ni alloy systems by means of Korringa-Kohn-Rostoker method with coherent potential approximation (KKR-CPA). The electrical resistivity was then calculated from the Kubo-Greenwood formula. These experimental and theoretical results show excellent agreement with each other, and the first principles results show the saturation behavior at high silicon concentration. We further calculated the resistivity of Fe-Ni-Si ternary alloys and found the violation of the Matthiessen's rule as a consequence of the resistivity saturation. Such resistivity saturation has important implications for core dynamics. The saturation effect places the upper limit of the resistivity, resulting in that the total resistivity value has almost no temperature dependence. As a consequence, the core thermal conductivity has a lower bound and exhibits a linear temperature dependence. We predict the electrical resistivity at the top of the Earth's core to be 1.12 ×10-6 Ωm, which corresponds to the thermal conductivity of 87.1 W/m/K. Such high thermal conductivity suggests high isentropic heat flow, leading to young inner core age (<0.85 Gyr old) and high initial

Manipulation of Spin-Torque Generation Using Ultrathin Au

NASA Astrophysics Data System (ADS)

An, Hongyu; Haku, Satoshi; Kanno, Yusuke; Nakayama, Hiroyasu; Maki, Hideyuki; Shi, Ji; Ando, Kazuya

2018-06-01

The generation and the manipulation of current-induced spin-orbit torques are of essential interest in spintronics. However, in spite of the vital progress in spin orbitronics, electric control of the spin-torque generation still remains elusive and challenging. We report on electric control of the spin-torque generation using ionic-liquid gating of ultrathin Au. We show that by simply depositing a SiO2 capping layer on an ultrathin-Au /Ni81Fe19 bilayer, the spin-torque generation efficiency is drastically enhanced by a maximum of 7 times. This enhancement is verified to be originated from the rough ultrathin-Au /Ni81Fe19 interface induced by the SiO2 deposition, which results in the enhancement of the interface spin-orbit scattering. We further show that the spin-torque generation efficiency from the ultrathin Au film can be reversibly manipulated by a factor of 2 using the ionic gating with an external electric field within a small range of 1 V. These results pave a way towards the efficient control of the spin-torque generation in spintronic applications.

Nano-sized Superlattice Clusters Created by Oxygen Ordering in Mechanically Alloyed Fe Alloys

NASA Astrophysics Data System (ADS)

Hu, Yong-Jie; Li, Jing; Darling, Kristopher A.; Wang, William Y.; Vanleeuwen, Brian K.; Liu, Xuan L.; Kecskes, Laszlo J.; Dickey, Elizabeth C.; Liu, Zi-Kui

2015-07-01

Creating and maintaining precipitates coherent with the host matrix, under service conditions is one of the most effective approaches for successful development of alloys for high temperature applications; prominent examples include Ni- and Co-based superalloys and Al alloys. While ferritic alloys are among the most important structural engineering alloys in our society, no reliable coherent precipitates stable at high temperatures have been found for these alloys. Here we report discovery of a new, nano-sized superlattice (NSS) phase in ball-milled Fe alloys, which maintains coherency with the BCC matrix up to at least 913 °C. Different from other precipitates in ferritic alloys, this NSS phase is created by oxygen-ordering in the BCC Fe matrix. It is proposed that this phase has a chemistry of Fe3O and a D03 crystal structure and becomes more stable with the addition of Zr. These nano-sized coherent precipitates effectively double the strength of the BCC matrix above that provided by grain size reduction alone. This discovery provides a new opportunity for developing high-strength ferritic alloys for high temperature applications.

Element Specific Spin and Orbital Moments in Fe1-x Vx Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan, Y.; Scheck, C; Bailey, W

2009-01-01

We present transmission-mode X-ray magnetic circular dichroism (XMCD) measurements of element-specific magnetic moments for Fe and V at the L2,3 edges in polycrystalline Fe1-xVx ultrathin films. We find that the orbital-to-spin moment ratio of Fe does not change within experimental error. The V XMCD is not very informative, and a nearly pure-spin type V impurity moment ({approx}1.0 {mu}{sub B}/atom, antiparallel to the Fe host moment) is assumed to match known magnetization data. Data are further reduced to a two-sublattice model and found to be compatible with known spectroscopic splitting g-factor data in the alloy. The results confirm that the verymore » low Gilbert damping, attained through the introduction of V into epitaxial Fe1-xVx films and found by ferromagnetic resonance (FMR), does not result from the reduction of orbital moment content in the alloy.« less

The effect of carbon distribution on deformation and cracking of Ni-16Cr-9Fe-C alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hertzberg, J.L.; Was, G.S.

1995-12-31

Constant extension rate tensile (CERT) tests and constant load tensile (CLT) tests were conducted on controlled purity Ni-16Cr-9Fe-C alloys. The amount and form of carbon were varied in order to investigate the roles of carbon in solution and as intergranular (IG) carbides in the deformation and IG cracking behavior in 360 C argon and primary water environments. Results show that the strength, ductility and creep resistance of these alloys are increased with carbon present in solid solution, while IG cracking on the fracture surface is suppressed. Alloys containing carbon in the form of IG carbides, however, exhibit reduced strength andmore » ductility relative to carbon in solution, while maintaining high IG cracking resistance with respect to carbon-free alloys. CERT results of commercial alloy 600 and controlled purity, carbon containing alloys yield comparable failure strains and IG cracking amounts. CLT comparisons with creep tests of alloy 600 suggest that alloys containing IG carbides are more susceptible to creep than those containing all carbon in solid solution.« less

Ultrathin Au-Alloy Nanowires at the Liquid-Liquid Interface.

PubMed

Chatterjee, Dipanwita; Shetty, Shwetha; Müller-Caspary, Knut; Grieb, Tim; Krause, Florian F; Schowalter, Marco; Rosenauer, Andreas; Ravishankar, Narayanan

2018-03-14

Ultrathin bimetallic nanowires are of importance and interest for applications in electronic devices such as sensors and heterogeneous catalysts. In this work, we have designed a new, highly reproducible and generalized wet chemical method to synthesize uniform and monodispersed Au-based alloy (AuCu, AuPd, and AuPt) nanowires with tunable composition using microwave-assisted reduction at the liquid-liquid interface. These ultrathin alloy nanowires are below 4 nm in diameter and about 2 μm long. Detailed microstructural characterization shows that the wires have an face centred cubic (FCC) crystal structure, and they have low-energy twin-boundary and stacking-fault defects along the growth direction. The wires exhibit remarkable thermal and mechanical stability that is critical for important applications. The alloy wires exhibit excellent electrocatalytic activity for methanol oxidation in an alkaline medium.

Elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys studied by the combinatorial thin film approach and ab initio calculations.

PubMed

Reeh, S; Kasprzak, M; Klusmann, C D; Stalf, F; Music, D; Ekholm, M; Abrikosov, I A; Schneider, J M

2013-06-19

The elastic properties of fcc Fe-Mn-X (X = Cr, Co, Ni, Cu) alloys with additions of up to 8 at.% X were studied by combinatorial thin film growth and characterization and by ab initio calculations using the disordered local moments (DLM) approach. The lattice parameter and Young's modulus values change only marginally with X. The calculations and experiments are in good agreement. We demonstrate that the elastic properties of transition metal alloyed Fe-Mn can be predicted by the DLM model.

Tunable dimensional crossover and magnetocrystalline anisotropy in Fe 2 P -based alloys

DOE PAGES

Zhuravlev, I. A.; Antropov, V. P.; Vishina, A.; ...

2017-10-01

Electronic structure calculations are used to examine the magnetic properties of Fe 2P-based alloys and the mechanisms through which the Curie temperature and magnetocrystalline anisotropy can be optimized for specific applications. It is found that at elevated temperatures the magnetic interaction in pure Fe 2P develops a pronounced two-dimensional character due to the suppression of the magnetization in one of the sublattices, but the interlayer coupling is very sensitive to band filling and structural distortions. This feature suggests a natural explanation of the observed sharp enhancement of the Curie temperature by alloying with multiple elements, such as Co, Ni, Si,more » and B. The magnetocrystalline anisotropy is also tunable by electron doping, reaching a maximum near the electron count of pure Fe 2P. These findings enable the optimization of the alloy content, suggesting co-alloying of Fe 2P with Co (or Ni) and Si as a strategy for maximizing the magnetocrystalline anisotropy at and above room temperature.« less

Hydrogen embrittlement in compositionally complex FeNiCoCrMn FCC solid solution alloy

DOE PAGES

Nygren, K. E.; Bertsch, K. M.; Wang, S.; ...

2018-02-01

The influence of internal hydrogen on the tensile properties of an equi-molar FeNiCoCrMn alloy results in a significant reduction of ductility, which is accompanied by a change in the fracture mode from ductile microvoid coalescence to intergranular failure. The introduction of 146.9 mass ppm of hydrogen reduced the plastic strain to failure from 0.67 in the uncharged case to 0.34 and 0.51 in hydrogen-charged specimens. This reduction in ductility and the transition in failure mode are clear indications that this alloy exhibits the classic signs of being susceptible to hydrogen embrittlement. The results are discussed in terms of the hydrogen-enhancedmore » plasticity mechanism and its influence on hydrogen-induced intergranular failure. Furthermore, a new additional constraint that further promotes intergranular failure is introduced for the first time.« less

Influence of Na+, K+, Mn2+, Fe2+ and Zn2+ ions on the electrodeposition of Ni-Co alloys: Implications for the recycling of Ni-MH batteries

NASA Astrophysics Data System (ADS)

Blanco, S.; Orta-Rodriguez, R.; Delvasto, P.

2017-01-01

A hydrometallurgical recycling procedure for the recovery of a mixed rare earths sulfate and an electrodeposited Ni-Co alloy has been described. The latter step was found to be complex, due to the presence of several ions in the battery electrode materials. Electrochemical evaluation of the influence of the ions on the Ni-Co alloy deposition was carried out by cyclic voltammetry test. It was found that ions such as K+, Fe2+ and Mn2+ improved the current efficiency for the Ni-Co deposition process on a copper surface. On the other hand, Na+ and Zn2+ ions exhibited a deleterious behaviour, minimizing the values of the reduction current. The results were used to suggest the inclusion of additional steps in the process flow diagram of the recycling operation, in order to eliminate deleterious ions from the electroplating solution.

Tribological Properties of AlCrCuFeNi2 High-Entropy Alloy in Different Conditions

NASA Astrophysics Data System (ADS)

Liu, Yong; Ma, Shengguo; Gao, Michael C.; Zhang, Chuan; Zhang, Teng; Yang, Huijun; Wang, Zhihua; Qiao, Junwei

2016-07-01

In order to understand the environmental effect on the mechanical behavior of high-entropy alloys, the tribological properties of AlCrCuFeNi2 are studied systematically in dry, simulated rainwater, and deionized water conditions against the Si3N4 ceramic ball at a series of different normal loads. The present study shows that both the friction and wear rate in simulated rainwater are the lowest. The simulated rainwater plays a significant role in the tribological behavior with the effect of forming passive film, lubricating, cooling, cleaning, and corrosion. The wear mechanism in simulated rainwater is mainly adhesive wear accompanied by abrasive wear as well as corrosive wear. In contrast, those in dry condition and deionized water are abrasive wear, adhesive wear, and surface plastic deformation. Oxidation contributes to the wear behavior in dry condition but is prevented in liquid condition. In addition, the phase diagram of Al x CrCuFeNi2 is predicted using CALPHAD modeling, which is in good agreement with the literature report and the present study.

Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys.

PubMed

Lu, Chenyang; Jin, Ke; Béland, Laurent K; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M; Stoller, Roger E; Wang, Lumin

2016-02-01

Energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters far exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance.

Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys

PubMed Central

Lu, Chenyang; Jin, Ke; Béland, Laurent K.; Zhang, Feifei; Yang, Taini; Qiao, Liang; Zhang, Yanwen; Bei, Hongbin; Christen, Hans M.; Stoller, Roger E.; Wang, Lumin

2016-01-01

Energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters far exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance. PMID:26829570

Shock Compression and Melting of an Fe-Ni-Si Alloy: Implications for the Temperature Profile of the Earth's Core and the Heat Flux Across the Core-Mantle Boundary

NASA Astrophysics Data System (ADS)

Zhang, Youjun; Sekine, Toshimori; Lin, Jung-Fu; He, Hongliang; Liu, Fusheng; Zhang, Mingjian; Sato, Tomoko; Zhu, Wenjun; Yu, Yin

2018-02-01

Understanding the melting behavior and the thermal equation of state of Fe-Ni alloyed with candidate light elements at conditions of the Earth's core is critical for our knowledge of the region's thermal structure and chemical composition and the heat flow across the liquid outer core into the lowermost mantle. Here we studied the shock equation of state and melting curve of an Fe-8 wt% Ni-10 wt% Si alloy up to 250 GPa by hypervelocity impacts with direct velocity and reliable temperature measurements. Our results show that the addition of 10 wt% Si to Fe-8 wt% Ni alloy slightly depresses the melting temperature of iron by 200-300 (±200) K at the core-mantle boundary ( 136 GPa) and by 600-800 (±500) K at the inner core-outer core boundary ( 330 GPa), respectively. Our results indicate that Si has a relatively mild effect on the melting temperature of iron compared with S and O. Our thermodynamic modeling shows that Fe-5 wt% Ni alloyed with 6 wt% Si and 2 wt% S (which has a density-velocity profile that matches the outer core's seismic profile well) exhibits an adiabatic profile with temperatures of 3900 K and 5300 K at the top and bottom of the outer core, respectively. If Si is a major light element in the core, a geotherm modeled for the outer core indicates a thermal gradient of 5.8-6.8 (±1.6) K/km in the D″ region and a high heat flow of 13-19 TW across the core-mantle boundary.

Microstructural Evolution of AlCoCrFeNiSi High-Entropy Alloy Powder during Mechanical Alloying and Its Coating Performance

PubMed Central

Fu, Ming; Xiong, Wei

2018-01-01

High-entropy alloys (HEAs) are promising structural materials due to their excellent comprehensive performances. The use of mechanically alloyed powders to deposit HEA coatings through atmospheric plasma spraying (APS) is an effective approach that can broaden the application areas of the HEAs. In this paper, a ductility–brittleness AlCoCrFeNiSi system was chosen as an object of study, and the detailed evolution of the surface morphology, particle size distribution, and microstructure of the powder during mechanical alloying was investigated. An AlCoCrFeNiSi HEA coating was deposited using powder milled for 10 h, which can be used as an ideal feedstock for APS. The surface morphology, microstructure, microhardness, and wear behavior of the coating at room temperature were investigated. The results showed that as the milling time increased, the particle size first increased, and then decreased. At the milling time of 10 h, simple body-centered cubic (BCC) and face-centered cubic (FCC) solid solution phases were formed. After spraying, the lamellar structure inside a single particle disappeared. An ordered BCC phase was detected, and the diffraction peaks of the Si element also disappeared, which indicates that phase transformation occurred during plasma spraying. A transmission electron microscopy analysis showed that nanometer crystalline grains with a grain size of about 30 nm existed in the APS coating. For the coating, an average microhardness of 612 ± 41 HV was obtained. Adhesive wear, tribo-oxidation wear, and slight abrasion wear took place during the wear test. The coating showed good wear resistance, with a volume wear rate of 0.38 ± 0.08 × 10−4 mm3·N−1·m−1, which makes it a promising coating for use in abrasive environments. PMID:29473872

Photoelectrochemical Water Splitting Properties of Ti-Ni-Si-O Nanostructures on Ti-Ni-Si Alloy

PubMed Central

Dong, Zhenbiao; Ning, Congqin

2017-01-01

Ti-Ni-Si-O nanostructures were successfully prepared on Ti-1Ni-5Si alloy foils via electrochemical anodization in ethylene glycol/glycerol solutions containing a small amount of water. The Ti-Ni-Si-O nanostructures were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and diffuse reflectance absorption spectra. Furthermore, the photoelectrochemical water splitting properties of the Ti-Ni-Si-O nanostructure films were investigated. It was found that, after anodization, three different kinds of Ti-Ni-Si-O nanostructures formed in the α-Ti phase region, Ti2Ni phase region, and Ti5Si3 phase region of the alloy surface. Both the anatase and rutile phases of Ti-Ni-Si-O oxide appeared after annealing at 500 °C for 2 h. The photocurrent density obtained from the Ti-Ni-Si-O nanostructure photoanodes was 0.45 mA/cm2 at 0 V (vs. Ag/AgCl) in 1 M KOH solution. The above findings make it feasible to further explore excellent photoelectrochemical properties of the nanostructure-modified surface of Ti-Ni-Si ternary alloys. PMID:29088083

Photoelectrochemical Water Splitting Properties of Ti-Ni-Si-O Nanostructures on Ti-Ni-Si Alloy.

PubMed

Li, Ting; Ding, Dongyan; Dong, Zhenbiao; Ning, Congqin

2017-10-31

Ti-Ni-Si-O nanostructures were successfully prepared on Ti-1Ni-5Si alloy foils via electrochemical anodization in ethylene glycol/glycerol solutions containing a small amount of water. The Ti-Ni-Si-O nanostructures were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and diffuse reflectance absorption spectra. Furthermore, the photoelectrochemical water splitting properties of the Ti-Ni-Si-O nanostructure films were investigated. It was found that, after anodization, three different kinds of Ti-Ni-Si-O nanostructures formed in the α-Ti phase region, Ti₂Ni phase region, and Ti₅Si₃ phase region of the alloy surface. Both the anatase and rutile phases of Ti-Ni-Si-O oxide appeared after annealing at 500 °C for 2 h. The photocurrent density obtained from the Ti-Ni-Si-O nanostructure photoanodes was 0.45 mA/cm² at 0 V (vs. Ag/AgCl) in 1 M KOH solution. The above findings make it feasible to further explore excellent photoelectrochemical properties of the nanostructure-modified surface of Ti-Ni-Si ternary alloys.

Pressure-induced fcc to hcp phase transition in Ni-based high entropy solid solution alloys

DOE PAGES

Zhang, Fuxiang; Zhao, Shijun; Jin, Ke; ...

2017-01-04

In this research, pressure-induced phase transition from the fcc to a hexagonal close-packed (hcp) structure wasfound in NiCoCrFe solid solution alloy starting at 13.5 GPa. The phase transition is very sluggish and the transition did not complete at ~ 40 GPa. The hcp structure is quenchable to ambient pressure. Only a very small amount (<5%) of hcp phase was found in the isostructural NiCoCr ternary alloy up to the pressure of 45 GPa and no obvious hcp phase was found in NiCoCrFePd system till to 74 GPa. Ab initio Gibbs free energy calculations indicated the energy differences between the fccmore » and the hcp phases for the three alloys are very small, but they are sensitive to temperature. Finally, the critical transition pressure in NiCoCrFe varies from 1 GPa at room temperature to 6 GPa at 500 K.« less

Pressure-induced fcc to hcp phase transition in Ni-based high entropy solid solution alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, F. X.; Zhao, Shijun; Jin, Ke

2017-01-04

A pressure-induced phase transition from the fcc to a hexagonal close-packed (hcp) structure was found in NiCoCrFe solid solution alloy starting at 13.5 GPa. The phase transition is very sluggish and the transition did not complete at ~40 GPa. The hcp structure is quenchable to ambient pressure. Only a very small amount (<5%) of hcp phase was found in the isostructural NiCoCr ternary alloy up to the pressure of 45 GPa and no obvious hcp phase was found in NiCoCrFePd system till to 74 GPa. Ab initio Gibbs free energy calculations indicated the energy differences between the fcc and themore » hcp phases for the three alloys are very small, but they are sensitive to temperature. The critical transition pressure in NiCoCrFe varies from ~1 GPa at room temperature to ~6 GPa at 500 K.« less

Development of weldable, corrosion-resistant iron-aluminide (FeAl) alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.

1997-04-01

A boron-microalloyed FeAl alloy (Fe-36Al-0.2Mo-0.05Zr-0.13C, at.%, with 100-400 appm B) with improved weldability and mechanical properties was developed in FY 1994. A new scale-up and industry technology development phase for this work began in FY 1995, pursuing two parallel paths. One path was developing monolithic FeAl component and application technology, and the other was developing coating/cladding technology for alloy steels, stainless steels and other Fe-Cr-Ni alloys. In FY 1995, it was found that cast FeAl alloys had good strength at 700-750{degrees}C, and some (2.5%) ductility in air at room-temperature. Hot-extruded FeAl with refined grain size was found to have ductilitymore » and to also have good impact-toughness at room-temperature. Further, it was discovered that powder-metallurgy (P/M) FeAl, consolidated by direct hot-extrusion at 950-1000{degrees}C to have an ultra fine-grained microstructure, had the highest ductility, strength and impact-toughness ever seen in such intermetallic alloys.« less

Patterned FePt nanostructures using ultrathin self-organized templates

NASA Astrophysics Data System (ADS)

Deng, Chen Hua; Zhang, Min; Wang, Fang; Xu, Xiao Hong

2018-02-01

Patterned magnetic thin films are both scientifically interesting and technologically useful. Ultrathin self-organized anodic aluminum oxide (AAO) template can be used to fabricate large area nanodot and antidot arrays. The magnetic properties of these nanostructures may be tuned by the morphology of the AAO template, which in turn can be controlled by synthetic parameters. In this work, ultrathin AAO templates were used as etching masks for the fabrication of both FePt nanodot and antidot arrays with high areal density. The perpendicular magnetic anisotropy of L10 FePt thin films are preserved in the nanostructures.

Freestanding NiFe Oxyfluoride Holey Film with Ultrahigh Volumetric Capacitance for Flexible Asymmetric Supercapacitors.

PubMed

Liang, Kun; Marcus, Kyle; Yang, Zhenzhong; Zhou, Le; Pan, Hao; Bai, Yuanli; Du, Yingge; Engelhard, Mark H; Yang, Yang

2018-01-01

In this work, a freestanding NiFe oxyfluoride (NiFeOF) holey film is prepared by electrochemical deposition and anodic treatments. With the combination of good electrical conductivity and holey structure, the NiFeOF holey film offers superior electrochemical performance with maximum specific capacitance of 670 F cm -3 (134 mF cm -2 ), due to the following reasons: (i) The residual metal alloy framework can be used as the current collector to improve electrode conductivity. Moreover, the as-prepared freestanding NiFeOF holey film can be used as a supercapacitor electrode without reliance on binders and other additives. The residual metal alloy framework and binder-free electrode effectively reduce electrode resistance, thus improving electron transport. (ii) The highly interconnected holey structure and hierarchical pore distribution provide a high specific surface area to improve electron transport, enhancing rapid ion transport, and mitigating diffusion limitations throughout the holey film. (iii) The excellent mechanical characteristics facilitate flexibility and cyclability related performance. Additionally, the NiFeOF holey film presents exceptional electrochemical performance, showing that it is a promising alternative for small/microsize electronic devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of High Damping Fe-Cr-Mo and Fe-Cr-Al Alloys for Naval Ships Application.

DTIC Science & Technology

1988-03-01

austenitic , and martensitic. The high damping Fe-Cr-based alloys are closely related to ferritic stainless steels . Ferritic stainless steel consists of an Fe...cm reveme it Prectiaq #no ’uenf r oy o.o(a tflrowf U S9GO..P Damping; Ship Silencing; Ferritic Stainless Steels ; Ti-Ni 7 LhV I,. Cintunue on roere .r...decreased. E. METALLURGY OF THE IRON-CHROMIUM ALLOY SYSTEM 1. Physical Properties Stainless steels are divided into three main classes: ferritic

The chromium doping of Ni{sub 3}Fe alloy and restructuring of grain boundary ensemble at the phase transition A1→L1{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perevalova, Olga; Konovalova, Elena, E-mail: knv123@yandex.ru; Koneva, Nina

2016-01-15

The grain boundary structure of the Ni{sub 3}(Fe,Cr) alloy is studied in states with a short and long-range order formed at the phase transition A1→L1{sub 2}. It is found that the new boundaries of general and special types are formed during an ordering annealing, wherein the special boundaries share increases. The spectrum of special boundaries is changed due to decreasing of ∑3 boundary share. It leads to weakening of the texture in the alloy with atomic long-range order. The features of change of the special boundaries spectrum at the phase transition A1→L1{sub 2} in the Ni{sub 3}(Fe,Cr) alloy are determinedmore » by decreasing of the stacking fault energy and the atomic mean square displacement at the chromium doping.« less

Steam Oxidation Behavior of Advanced Steels and Ni-Based Alloys at 800 °C

NASA Astrophysics Data System (ADS)

Dudziak, T.; Boroń, L.; Deodeshmukh, V.; Sobczak, J.; Sobczak, N.; Witkowska, M.; Ratuszek, W.; Chruściel, K.

2017-03-01

This publication studies the steam oxidation behavior of advanced steels (309S, 310S and HR3C) and Ni-based alloys (Haynes® 230®, alloy 263, alloy 617 and Haynes® 282®) exposed at 800 °C for 2000 h under 1 bar pressure, in a pure water steam system. The results revealed that all exposed materials showed relatively low weight gain, with no spallation of the oxide scale within the 2000 h of exposure. XRD analysis showed that Ni-based alloys developed an oxide scale consisting of four main phases: Cr2O3 (alloy 617, Haynes® 282®, alloy 263 and Haynes® 230®), MnCr2O4 (alloy 617, Haynes® 282® and Haynes® 230®), NiCr2O4 (alloy 617) and TiO2 (alloy 263, Haynes® 282®). In contrast, advanced steels showed the development of Cr2O3, MnCr2O4, Mn7SiO12, FeMn(SiO4) and SiO2 phases. The steel with the highest Cr content showed the formation of Fe3O4 and the thickest oxide scale.

Development of a Brazing Alloy for the Mechanically Alloyed High Temperature Sheet Material INCOLOY Alloy MA 956.

DTIC Science & Technology

1981-09-01

OF A BRAZING ALLOY FOR THE MECHANICALLY ALLOYED HIGH TEMPERATURE SHEET MATERIAL INCOLOY ALLOY MA 956 W. E. Morgan and Dr. P. J. Bridges N. Wiggin...PERIOD COVERED DEVELOPMENT OF A BRAZING ALLOY FOR THE Final Report MECHANICALLY ALLOYED HIGH TEMPERATURE Dec 1978 - March 1981 SHEET MATERIAL INCOLOY...block nomber) High temperature ODS alloys, Braze development, Braze alloys, INCOLOY MA 956, Ni-Cr-Pd, Fe-Cr-Pd, Ni-Cr-Ge, Fe-Cr-Ge, Fe-Cr-B, Fe-Cr-Si

Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

NASA Technical Reports Server (NTRS)

Lowell, C. E.; Deadmore, D. L.; Whittenberger, J. D.

1982-01-01

Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100 C and hot corrosion at 900 C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to about 2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving 3800 oxidation and 2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only about 1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

Investigation into nanoscratching mechanical response of AlCrCuFeNi high-entropy alloys using atomic simulations

NASA Astrophysics Data System (ADS)

Wang, Zining; Li, Jia; Fang, QiHong; Liu, Bin; Zhang, Liangchi

2017-09-01

The mechanical behaviors and deformation mechanisms of scratched AlCrCuFeNi high entropy alloys (HEAs) have been studied by molecular dynamics (MD) simulations, in terms of the scratching forces, atomic strain, atomic displacement, microstructural evolution and dislocation density. The results show that the larger tangential and normal forces and higher friction coefficient take place in AlCrCuFeNi HEA due to its outstanding strength and hardness, and high adhesion and fracture toughness over the pure metal materials. Moreover, the stacking fault energy (SFE) in HEA increases the probability to initiate dislocation and twinning, which is conducive to the formation of complex deformation modes. Compared to the single element metal workpieces, the segregation potency of solutes into twinning boundary (TB) is raised due to the decreasing segregation energy of TB, resulting in the stronger solute effects on improving twinning properties for HEA workpiece. The higher dislocation density and the more activated slipping planes lead to the outstanding plasticity of AlCrCuFeNi HEA. The solute atoms as barriers to hinder the motion of dislocation and the severe lattice distortion to suppress the free slipping of dislocation are significantly stronger obstacles to strengthen HEA. The excellent comprehensive scratching properties of the bulk AlCrCuFeNi HEAs are associated with the combined effects of multiple strengthening mechanisms, such as dislocation strengthening, deformation twinning strengthening as well as solute strengthening. This work provides a basis for further understanding and tailoring SFE in mechanical properties and deformation mechanism of HEAs, which maybe facilitate the design and preparation of new HEAs with high performance.

Layered structure and related magnetic properties for annealed Fe/Ir(111) ultrathin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Pei-Cheng; Chen, Wei-Hsiang; Hsieh, Chen-Yuan

2015-05-07

After annealing treatments for fcc-Fe/Ir(111) below 600 K, the surface layers remain pseudomorphic. The Ir(111) substrate plays an important role on the expanded Fe lattice. At temperatures between 750 and 800 K, the surface composition shows a stable state and a c(2 × 4) structure is observed. We discover a layered structure composed of some Fe atoms on the top of a Fe{sub 0.5}Ir{sub 0.5} interfacial alloy supported on the Ir(111) substrate. The competition between the negative formation heat of Fe{sub 0.5}Ir{sub 0.5} and surface free energy of Fe causes the formation of layered structure. The existence of ferromagnetic dead layer coincides with themore » formation of fcc-Fe for ultrathin Fe on Fe{sub 0.5}Ir{sub 0.5}/Ir(111). For Fe films thicker than three monolayers, the linear increase of the Kerr intensity versus the Fe coverage is related to the growing of bcc-Fe on the surface where the Fe layer is incoherent to the underlying Fe{sub 0.5}Ir{sub 0.5}/Ir(111). These results emphasize the importance of the substrate induced strain and layered structure of Fe/Fe{sub 0.5}Ir{sub 0.5}/Ir(111) on the magnetic properties and provide valuable information for future applications.« less

The cyclic oxidation resistance at 1200 C of beta-NiAl, FeAl, and CoAl alloys with selected third element additions

NASA Technical Reports Server (NTRS)

Barrett, C. A.; Titran, R. H.

1992-01-01

The intermetallic compounds Beta-NiAl, FeAl, and CoAl were tested in cyclic oxidation with selected third element alloy additions. Tests in static air for 200 1-hr cycles at 1200 C indicated by specific weight change/time data and x-ray diffraction analysis that the 5 at percent alloy additions did not significantly improve the oxidation resistance over the alumina forming baseline alloys without the additions. Many of the alloy additions were actually deleterious. Ta and Nb were the only alloy additions that actually altered the nature of the oxide(s) formed and still maintained the oxidation resistance of the protective alumina scale.

Superelasticity, corrosion resistance and biocompatibility of the Ti-19Zr-10Nb-1Fe alloy.

PubMed

Xue, Pengfei; Li, Yan; Li, Kangming; Zhang, Deyuan; Zhou, Chungen

2015-05-01

Microstructure, mechanical properties, superelasticity and biocompatibility of a Ti-19Zr-10Nb-1Fe alloy are investigated. X-ray diffraction spectroscopy and transmission electron microscopy observations show that the as-cast Ti-19Zr-10Nb-1Fe alloy is composed of α' and β phases, but only the β phase exists in the as-rolled and as-quenched alloys. The tensile stress-strain tests indicate that the as-quenched alloy exhibits a good combination of mechanical properties with a large elongation of 25%, a low Young's modulus of 59 GPa and a high ultimate tensile stress of 723 MPa. Superelastic recovery behavior is found in the as-quenched alloy during tensile tests, and the corresponding maximum of superelastic strain is 4.7% at the pre-strain of 6%. A superelastic recovery of 4% with high stability is achieved after 10 cyclic loading-unloading training processes. Potentiodynamic polarization and ion release measurements indicate that the as-quenched alloy shows a lower corrosion rate in Hank's solution and a much less ion release rate in 0.9% NaCl solution than those of the NiTi alloys. Cell culture results indicate that the osteoblasts' adhesion and proliferation are similar on both the Ti-19Zr-10Nb-1Fe and NiTi alloys. A better hemocompatibility is confirmed for the as-quenched Ti-19Zr-10Nb-1Fe alloy, attributed to more stable platelet adhesion and small activation degree, and a much lower hemolysis rate compared with the NiTi alloy. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis, characterization and magnetic properties of nanocrystalline FexNi80-xCo20 ternary alloys

NASA Astrophysics Data System (ADS)

Dalavi, Shankar B.; Theerthagiri, J.; Raja, M. Manivel; Panda, R. N.

2013-10-01

Fe-Ni-Co alloys of various compositions (FexNi80-xCo20,x=20-50) were synthesized by using a sodium borohydride reduction route. The phase purity and crystallite size was ascertained by using powder X-ray diffraction (XRD). The alloys crystallize in the face centered cubic (fcc) structure with lattice parameters, a=3.546-3.558 Å. The XRD line broadening indicates the fine particle nature of the materials. The estimated crystallite sizes were found to be 27.5, 27, 24, and 22.8 nm for x=20, 30, 40, and 50; alloys respectively. Scanning electron micrograph studies indicates particle sizes to be in the range of 83-60 nm for Fe-Ni-Co alloys. The values of saturation magnetization for FexNi80-xCo20 are found to be in the range of 54.3-41.2 emu/g and are significantly lower than the bulk values (175-180 emu/g). The coercivity decreases from 170 to 122 Oe with decrease in Fe content. The observed magnetic behavior has been explained on the basis of size, surface effects, spin canting and the presence of superparamagnetic fractions in the ultrafine materials.

Microstructure and mechanical properties of friction stir welded and laser welded high entropy alloy CrMnFeCoNi

NASA Astrophysics Data System (ADS)

Jo, Min-Gu; Kim, Han-Jin; Kang, Minjung; Madakashira, Phaniraj P.; Park, Eun Soo; Suh, Jin-Yoo; Kim, Dong-Ik; Hong, Sung-Tae; Han, Heung Nam

2018-01-01

The high entropy alloy CrMnFeCoNi has been shown to have promising structural properties. For a new alloy to be used in a structural application it should be weldable. In the present study, friction stir welding (FSW) and laser welding (LW) techniques were used to butt weld thin plates of CrMnFeCoNi. The microstructure, chemical homogeneity and mechanical behavior of the welds were characterized and compared with the base metal. The tensile stress-strain behavior of the welded specimens were reasonable when compared with that of the base metal. FSW refined the grain size in the weld region by a factor of ˜14 when compared with the base metal. High-angle annular dark field transmission electron microscopy in combination with energy dispersive X-ray spectroscopy showed chemical inhomogeneity between dendritic and interdendritic regions in the fusion zone of LW. Large fluctuations in composition (up to 15 at%) did not change the crystal structure in the fusion zone. Hardness measurements were carried out in the weld cross section and discussed in view of the grain size, low angle grain boundaries and twin boundaries in FSW specimens and the dendritic microstructure in LW specimens.

Direct Observation of Defect Range and Evolution in Ion-Irradiated Single Crystalline Ni and Ni Binary Alloys

DOE PAGES

Lu, Chenyang; Jin, Ke; Béland, Laurent K.; ...

2016-02-01

We report that energetic ions have been widely used to evaluate the irradiation tolerance of structural materials for nuclear power applications and to modify material properties. It is important to understand the defect production, annihilation and migration mechanisms during and after collision cascades. In this study, single crystalline pure nickel metal and single-phase concentrated solid solution alloys of 50%Ni50%Co (NiCo) and 50%Ni50%Fe (NiFe) without apparent preexisting defect sinks were employed to study defect dynamics under ion irradiation. Both cross-sectional transmission electron microscopy characterization (TEM) and Rutherford backscattering spectrometry channeling (RBS-C) spectra show that the range of radiation-induced defect clusters farmore » exceed the theoretically predicted depth in all materials after high-dose irradiation. Defects in nickel migrate faster than in NiCo and NiFe. Both vacancy-type stacking fault tetrahedra (SFT) and interstitial loops coexist in the same region, which is consistent with molecular dynamics simulations. Kinetic activation relaxation technique (k-ART) simulations for nickel showed that small vacancy clusters, such as di-vacancies and tri-vacancies, created by collision cascades are highly mobile, even at room temperature. The slower migration of defects in the alloy along with more localized energy dissipation of the displacement cascade may lead to enhanced radiation tolerance.« less

Understanding self ion damage in FCC Ni-Cr-Fe based alloy using X-ray diffraction techniques

NASA Astrophysics Data System (ADS)

Halder Banerjee, R.; Sengupta, P.; Chatterjee, A.; Mishra, S. C.; Bhukta, A.; Satyam, P. V.; Samajdar, I.; Dey, G. K.

2018-04-01

Using X-ray diffraction line profile analysis (XRDLPA) approach the radiation response of FCC Ni-Cr-Fe based alloy 690 to 1.5 and 3 MeV Ni2+ ion damage was quantified in terms of its microstructural parameters. These microstructural parameters viz. average domain size, microstrain and dislocation density were found to vary anisotropically with fluence. The anisotropic behaviour is mainly attributable to presence of twins in pre-irradiated microstructure. After irradiation, surface roughness increases as a function of fluence attributable to change in surface and sub-surface morphology caused by displacement cascade, defects and sputtered atoms created by incident energetic ion. The radiation hardening in case of 1.5 MeV Ni2+ irradiated specimens too is a consequence of the increase in dislocation density formed by interaction of radiation induced defects with pre-existing dislocations. At highest fluence there is an initiation of saturation.

Pd-Pt and Fe-Ni nanoparticles formed by covalent molecular assembly in supercritical carbon dioxide.

PubMed

Puniredd, Sreenivasa Reddy; Weiyi, Seah; Srinivasan, M P

2008-04-01

We report the formation of Pd-Pt nanoparticles within a dendrimer-laden ultrathin film matrix immobilized on a solid support and constructed by covalent layer-by-layer (LbL) assembly using supercritical carbon dioxide (SCCO2) as the processing medium. Particle size distribution and composition were controlled by precursor composition. The precursor compositions are optimized for Pd-Pt nanoparticles and later extended to the formation of Fe-Ni nanoparticles. As an example of the application of nanoparticles in tribology, Fe-Ni nanoparticle-laden films were observed to exhibit better tribological properties than those containing the monometallic species, thereby suggesting that combination of nanoparticles can be used to derive greater benefits.

Deep Drawing Behavior of CoCrFeMnNi High-Entropy Alloys

NASA Astrophysics Data System (ADS)

Bae, Jae Wung; Moon, Jongun; Jang, Min Ji; Ahn, Dong-Hyun; Joo, Soo-Hyun; Jung, Jaimyun; Yim, Dami; Kim, Hyoung Seop

2017-09-01

Herein, the deep drawability and deep drawing behavior of an equiatomic CoCrFeMnNi HEA and its microstructure and texture evolution are first studied for future applications. The CoCrFeMnNi HEA is successfully drawn to a limit drawing ratio (LDR) of 2.14, while the planar anisotropy of the drawn cup specimen is negligible. The moderate combination of strain hardening exponent and strain rate sensitivity and the formation of deformation twins in the edge region play important roles in successful deep drawing. In the meanwhile, the texture evolution of CoCrFeMnNi HEA has similarities with conventional fcc metals.

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability.

PubMed

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-11-05

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics.

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability

PubMed Central

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-01-01

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics. PMID:29113096

Electronic structure, stability and magnetic properties of small M1-2Cr (M = Fe, Co, and Ni) alloy encapsulated inside a (BN)48 cage

NASA Astrophysics Data System (ADS)

Liang, Wenjuan; Jia, Jianfeng; Lv, Jin; Wu, Haishun

2015-09-01

The geometrical structure and magnetic properties of M1-2Cr (M = Fe, Co, and Ni) alloy clusters inside a (BN)48 cage were calculated at the BPW91/LANL2DZ level of theory. The doping with Cr significantly changed the magnetic properties of the transition-metal clusters. When M1-2Cr alloys were placed inside a (BN)48 cage, the alloy clusters interacted strongly with the cage, and the M1-2Cr@(BN)48 clusters showed high stability. Moreover, Cr-doped magnetic metal clusters preferably occupied positions off-center and near the hexagonal rings of (BN)48 cages. Thus, the (BN)48 cages can be used to increase the stability of M1-2Cr alloys, and retain their magnetic nature, except for CoCr and Ni2Cr clusters.

Enhancement of magnetocaloric effect by external hydrostatic pressure in MnNi0.75Fe0.25Ge alloy

NASA Astrophysics Data System (ADS)

Mandal, K.; Dutta, P.; Dasgupta, P.; Pramanick, S.; Chatterjee, S.

2018-06-01

A systematic investigation on the structural and magnetic properties of an Fe-doped MnNiGe alloy with nominal composition MnNi0.75Fe0.25Ge has been performed. Temperature dependent x-ray diffraction studies indicate a clear structural phase transition (martensitic type) from the high temperature hexagonal austenite phase (space group P63/mmc) to the low temperature orthorhombic martensite phase (space group Pnma). Interestingly, about 1.4% of the high temperature hexagonal phase has been observed at 15 K, which is well below the martensitic phase transition (MPT) temperature. The studied alloy is found to be ferromagnetic in nature at the lowest temperature of measurement and the saturation moment increases in the presence of external hydrostatic pressure (P). In addition, it shows a significantly large conventional (negative) magnetocaloric effect with an adiabatic entropy change () of about ‑16.2 J kg‑1 K‑1 around the MPT for a magnetic field changing from 0  →  5 T. The most interesting observation is the  ∼40.1% increase in the peak value of on application of 6 kbar of external P. A considerable increment in the refrigeration capacity has also been noted with the applied P.

Single crystal plastic behavior of a single-phase, face-center-cubic-structured, equiatomic FeNiCrCo alloy

DOE PAGES

Wu, Zhenggang; Gao, Y. F.; Bei, Hongbin

2015-07-25

To understand the fundamental deformation mechanisms of compositionally complex alloys, single crystals of a multi-component equiatomic FeNiCoCr alloy with face-centered cubic (FCC) structure were grown for mechanical studies. Similarly to typical FCC pure metals, slip trace analyses indicate that dislocation slips take place on (1 1 1) planes along [11¯0] directions. The critical resolved shear stress (CRSS) obeys the Schmid law at both 77 and 293 K, and tension–compression asymmetry is not observed. Although this material slips in a normal FCC manner both at 293 and 77 K, compared to typical FCC metals the CRSS’s strong temperature dependence is abnormal.

Phase relations of Fe-Si-Ni alloys at core conditions: Implications for the Earth inner core

NASA Astrophysics Data System (ADS)

Fiquet, G.; Boulard, E.; Auzende, A.; Antonangeli, D.; Badro, J.; Morard, G.; Siebert, J.; Perrillat, J.; Mezouar, M.

2008-12-01

The Earth core consists of a liquid outer core and a solid inner core, which are believed to be made predominantly of iron (Fe). Among all crystallographic structures proposed, a consensus has more or less emerged with the hexagonal closed packed structure -hcp- for iron. The question of the structure of this alloy at core conditions, in particular in vicinity of the melting line is however still largely debated. Among others, a possible thermal and chemical stabilization of body-centered cubic iron in the Earth's core has indeed been proposed with the theoretical calculations of Vocadlo et al. [Nature, 424, 536, 2003]. Recent X-ray experiments have shown the existence of such a bcc structure above 220 GPa at high-temperature for iron- nickel alloys [Dubrovinsky et al., Science, 316, 1880, 2007]. It is also known from density systematics that the Earth's core is made of iron alloyed with light elements [see Poirier, Phys. Earth Planet. Int., 85, 319, 1994]. We recently proposed a compositional model for the Earth's inner core from a systematic study of the effect of light elements on sound velocities at high pressure. Our preferred core model is an inner core which contains 2.3 wt % silicon and traces of oxygen [see Badro et al., Earth Planet. Sci. Lett., 254, 233, 2007 for more details]. Recent studies, however, suggest that small amount of silicon or nickel can substantially affect the phase relations and thermodynamic properties of iron alloys. We present results from an X-ray diffraction carried out at ESRF at high-pressure and high-temperature, using a state-of-the-art double sided laser heating system. We address the question of the structure of this alloy at core conditions. Two different alloys have been synthesized for this experiment, with Fe : 92.4, Si : 3.7, Ni 3.9 and Fe: 88.4, Si: 7.3, Ni: 4.3 in wt %, so as to satisfy the core preferred compositional model described in Badro et al. [2007]. The samples were loaded in a diamond anvil cell with neon as

Polyamorphic Transformations in Fe-Ni-C Liquids: Implications for Chemical Evolution of Terrestrial Planets: Fe-Ni-C liquid structural change

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Xiaojing; Chen, Bin; Wang, Jianwei

During the formation of the Earth's core, the segregation of metallic liquids from silicate mantle should have left behind evident geochemical imprints on both the mantle and the core. Some distinctive geochemical signatures of the mantle-derived rocks likely own their origin to the metal-silicate differentiation of the primitive Earth, setting our planet apart from undifferentiated meteorites as well as terrestrial planets or moons isotopically and compositionally. Understanding the chemical evolution of terrestrial planetary bodies requires knowledge on properties of both liquid iron alloys and silicates equilibrating under physicochemical conditions pertinent to the deep magma ocean. Here we report experimental andmore » computational results on the pressure-induced structural evolution of iron-nickel liquids alloyed with carbon. Our X-ray diffraction experiments up to 7.3 gigapascals (GPa) demonstrate that Fe-Ni (Fe90Ni10) liquids alloyed with 3 and 5 wt % carbon undergo a polyamorphic liquid structure transition at approximately 5 GPa. Corroborating the experimental observations, our first-principles molecular dynamic calculations reveal that the structural transitions result from the marked prevalence of three-atom face-sharing polyhedral connections in the liquids at >5 GPa. The structure and polyamorphic transitions of liquid iron-nickel-carbon alloys govern their physical and chemical properties and may thus cast fresh light on the chemical evolution of terrestrial planets and moons.« less

Thermomechanical treatment for improved neutron irradiation resistance of austenitic alloy (Fe-21Cr-32Ni)

DOE Office of Scientific and Technical Information (OSTI.GOV)

L. Tan; J. T. Busby; H. J. M. Chichester

2013-06-01

An optimized thermomechanical treatment (TMT) applied to austenitic alloy 800H (Fe-21Cr-32Ni) had shown significant improvements in corrosion resistance and basic mechanical properties. This study examined its effect on radiation resistance by irradiating both the solution-annealed (SA) and TMT samples at 500 degrees C for 3 dpa. Microstructural characterization using transmission electron microscopy revealed that the radiation-induced Frank loops, voids, and y'-Ni3(Ti,Al) precipitates had similar sizes between the SA and TMT samples. The amounts of radiation-induced defects and more significantly y' precipitates, however, were reduced in the TMT samples. These reductions would approximately reduce by 40.9% the radiation hardening compared tomore » the SA samples. This study indicates that optimized-TMT is an economical approach for effective overall property improvements.« less

Phase relationships of the system Fe-Ni-S and structure of the high-pressure phase of (Fe1-xNix)3S2

NASA Astrophysics Data System (ADS)

Urakawa, Satoru; Kamuro, Ryota; Suzuki, Akio; Kikegawa, Takumi

2018-04-01

The phase relationships of the Fe-Ni-S system at 15 GPa were studied by high pressure quench experiments. The stability fields of (Fe,Ni)3S and (Fe,Ni)3S2 and the melting relationships of the Fe-Ni-S system were determined as a function of Ni content. The (Fe,Ni)3S solid solution is stable in the composition of Ni/(Fe + Ni) > 0.7 and melts incongruently into an Fe-Ni alloy + liquid. The (Fe,Ni)3S2 makes a complete solid solution and melts incongruently into (Fe,Ni)S + liquid, whose structure was determined to show Cmcm-orthorhombic symmetry by in situ synchrotron X-ray diffraction experiments. The eutectic contains about 30 at.% of S, and its temperature decreases with increasing Ni content with a rate of ∼5 K/at.% from 1175 K. The density of the Fe-FeS eutectic composition (Fe70S30) liquid is evaluated to be 6.93 ± 0.08 g/cm3 at 15 GPa and 1200 K based on the Clausius-Clapeyron relations and densities of subsolidus phases. The Fe-Ni-S liquids are a primary sulfur-bearing phase in the deep mantle with a reducing condition (250-660 km depth), and they would play a significant role in the carbon cycle as a carbon host as well as in the generation of diamond.

Phase relations in the Fe-Ni-Cr-S system and the sulfidation of an austenitic stainless steel

NASA Technical Reports Server (NTRS)

Jacob, K. T.; Rao, D. B.; Nelson, H. G.

1977-01-01

The stability fields of various sulfide phases that form on Fe-Cr, Fe-Ni, Ni-Cr and Fe-Cr-Ni alloys were developed as a function of temperature and the partial pressure of sulfur. The calculated stability fields in the ternary system were displayed on plots of log P sub S sub 2 versus the conjugate extensive variable which provides a better framework for following the sulfidation of Fe-Cr-Ni alloys at high temperatures. Experimental and estimated thermodynamic data were used in developing the sulfur potential diagrams. Current models and correlations were employed to estimate the unknown thermodynamic behavior of solid solutions of sulfides and to supplement the incomplete phase diagram data of geophysical literature. These constructed stability field diagrams were in excellent agreement with the sulfide phases and compositions determined during a sulfidation experiment.

Oxidation behaviour of Fe-Ni alloy nanoparticles synthesized by thermal plasma route

NASA Astrophysics Data System (ADS)

Ghodke, Neha; Kamble, Shalaka; Raut, Suyog; Puranik, Shridhar; Bhoraskar, S. V.; Rayaprol, Sudhindra; Mathe, V. L.

2018-04-01

Here we report synthesis of Fe-Ni nanoparticles using thermal plasma route. In thermal plasma, gas phase nucleation and growth at sufficiently higher temperature is observed. The synthesized Fe-Ni nanoparticles are examined by X-ray Diffraction, Raman Spectroscopy, Vibrating Sample Magnetometer and Thermo gravimetric Analysis. Formation of 16-21 nm sized Fe-Ni nanoparticles having surface oxidation show maximum value of magnetization of ˜107 emu/g. The sample synthesized at relatively low power (4kW) show presence of carbonaceous species whereas the high power (6 kW) synthesis does not depicts carbonaceous species. The presence of carbonaceous species protects oxidation of the nanoparticles significantly as evidenced from TGA data.

The reactivity of Fe/Ni colloid stabilized by carboxymethylcellulose (CMC-Fe/Ni) toward chloroform.

PubMed

Jin, Xin; Li, Qun; Yang, Qi

2018-05-16

The use of stabilizers can prevent the reactivity loss of nanoparticles due to aggregation. In this study, carboxymethylcellulose (CMC) was selected as the stabilizer to synthesize a highly stable CMC-stabilized Fe/Ni colloid (CMC-Fe/Ni) via pre-aggregation stabilization. The reactivity of CMC-Fe/Ni was evaluated via the reaction of chloroform (CF) degradation. The effect of background solution which composition was affected by the preparation of Fe/Ni (Fe/Ni precursors, NaBH 4 dosage) and the addition of solute (common ions, sulfur compounds) on the reactivity of CMC-Fe/Ni was also investigated. Additionally, the dried CMC-Fe/Ni was used for characterization in terms of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The experimental results indicated that CMC stabilization greatly improved the reactivity of Fe/Ni bimetal and CF (10 mg/L) could be completely degraded by CMC-Fe/Ni (0.1 g/L) within 45 min. The use of different Fe/Ni precursors resulting in the variations of background solution seemed to have no obvious influence on the reactivity of CMC-Fe/Ni, whereas the dosage of NaBH 4 in background solution showed a negative correlation with the reactivity of CMC-Fe/Ni. Besides, the individual addition of external solutes into background solution all had an adverse effect on the reactivity of CMC-Fe/Ni, of which the poisoning effect of sulfides (Na 2 S, Na 2 S 2 O 4 ) was significant than common ions and sulfite.

Ni nanotube array-based electrodes by electrochemical alloying and de-alloying for efficient water splitting.

PubMed

Teng, Xue; Wang, Jianying; Ji, Lvlv; Lv, Yaokang; Chen, Zuofeng

2018-05-17

The design of cost-efficient earth-abundant catalysts with superior performance for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is extremely important for future renewable energy production. Herein, we report a facile strategy for constructing Ni nanotube arrays (NTAs) on a Ni foam (NF) substrate through cathodic deposition of NiCu alloy followed by anodic stripping of metallic Cu. Based on Ni NTAs, the as-prepared NiSe2 NTA electrode by NiSe2 electrodeposition and the NiFeOx NTA electrode by dipping in Fe3+ solution exhibit excellent HER and OER performance in alkaline conditions. In these systems, Ni NTAs act as a binder-free multifunctional inner layer to support the electrocatalysts, offer a large specific surface area and serve as a fast electron transport pathway. Moreover, an alkaline electrolyzer has been constructed using NiFeOx NTAs as the anode and NiSe2 NTAs as the cathode, which only demands a cell voltage of 1.78 V to deliver a water-splitting current density of 500 mA cm-2, and demonstrates remarkable stability during long-term electrolysis. This work provides an attractive method for the design and fabrication of nanotube array-based catalyst electrodes for highly efficient water-splitting.

The effect of minor additions of titanium on the fracture toughness of Fe-12Ni alloys at 77K

NASA Technical Reports Server (NTRS)

Conrad, H.; Yin, C.; Sargent, G.

1978-01-01

Titanium additions ranging from 0.18 to 0.99 atomic percent and heat treatments of 2 hours at 550, 685 and 820 C respectively followed by a water quench were considered. Cubic and rectangular shaped inclusions were noted in the SEM fractographs of the alloys with the Ti additions. A fine precipitate was observed by TEM for the Fe-12Ni-0.18Ti alloys heat treated at 550 C; this precipitate was not observed for the 685 and 820 C heat treatments of the same alloy. Auger mappings of the fracture surfaces indicated a weak to moderate association of the interstitials C, N and O with Ti, the degree of which depended on the particular interstitial and the heat treatment temperature.

The thermal expansion of (Fe1-y Ni y )Si.

PubMed

Hunt, Simon A; Wann, Elizabeth T H; Dobson, David P; Vočadlo, Lindunka; Wood, Ian G

2017-08-23

We have measured the thermal expansion of (Fe 1-y Ni y )Si for y  =  0, 0.1 and 0.2, between 40 and 1273 K. Above ~700 K the unit-cell volumes of the samples decrease approximately linearly with increasing Ni content. Below ~200 K the unit-cell volume of FeSi falls to a value between that of (Fe 0.9 Ni 0.1 )Si and (Fe 0.8 Ni 0.2 )Si. We attribute this extra contraction of the FeSi, which is a narrow band-gap semiconductor, to the depopulation of the conduction band at low temperatures; in the two alloys the additional electrons introduced by the substitution of Ni lead to the conduction band always being populated. We have fit the unit-cell volume data with a Debye internal energy model of thermal expansion and an additional volume term, above 800 K, to take account of the volumetric changes associated with changes in the composition of the sample. Using the thermophysical parameters of the fit we have estimated the band gap in FeSi to be 21(1) meV and the unit-cell volume change in FeSi associated with the depopulation of the conduction band to be 0.066(35) Å 3 /unit-cell.

Magnetocaloric effect in amorphous and partially crystallized Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18} alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thanveer, T.; Thomas, S., E-mail: senoythomas@gmail.com; Ramanujan, R. V.

A study of magnetocaloric effect in amorphous and partially crystallized Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18} alloys is reported. Amorphous Fe{sub 40}Ni{sub 38}Mo{sub 4}B{sub 18}, near its magnetic ordering temperature (600 K) showed a magnetic entropy change ΔS{sub M} of 1.1 J/KgK and a relative cooling power of 36 J/Kg in a field change of 10 kOe. Amorphous samples were partially crystallized by annealing at 700 K at different time intervals. Partially crystallized samples showed two distinct magnetic ordering temperature, one corresponding to the precipitated FeNi nanocrystals and the other one corresponding to the boron rich amorphous matrix. Magnetic ordering temperaturemore » of the residual amorphous matrix got shifted to the lower temperatures on increasing the annealing duration. Partially crystallised samples showed a magnetic entropy change of about 0.27 J/kgK near the magnetic ordering temperature of the amorphous matrix (540 K) in a field change of 10 kOe. The decrease in ΔS{sub M} on partial crystallisation is attributed to the biphasic magnetic nature of the sample.« less

Composition of the Earth's inner core from high-pressure sound velocity measurements in Fe-Ni-Si alloys

NASA Astrophysics Data System (ADS)

Antonangeli, Daniele; Siebert, Julien; Badro, James; Farber, Daniel L.; Fiquet, Guillaume; Morard, Guillaume; Ryerson, Frederick J.

2010-06-01

We performed room-temperature sound velocity and density measurements on a polycrystalline alloy, Fe0.89Ni0.04Si0.07, in the hexagonal close-packed (hcp) phase up to 108 GPa. Over the investigated pressure range the aggregate compressional sound velocity is ∼ 9% higher than in pure iron at the same density. The measured aggregate compressional (VP) and shear (VS) sound velocities, extrapolated to core densities and corrected for anharmonic temperature effects, are compared with seismic profiles. Our results provide constraints on the silicon abundance in the core, suggesting a model that simultaneously matches the primary seismic observables, density, P-wave and S-wave velocities, for an inner core containing 4 to 5 wt.% of Ni and 1 to 2 wt.% of Si.

Spinel FeCo2S4 nanoflower arrays grown on Ni foam as novel binder-free electrodes for long-cycle-life supercapacitors

NASA Astrophysics Data System (ADS)

Deng, Cuifen; Yang, Lishan; Yang, Chunming; Shen, Ping; Zhao, Liping; Wang, Zhiyu; Wang, Chunhui; Li, Junhua; Qian, Dong

2018-01-01

Spinel FeCo2S4 nanoflower arrays grown on Ni foam (FeCo2S4@Ni) have been successfully fabricated via a facile hydrothermal sulfurization of the corresponding FeCo2O4 precursor. The results of X-ray diffraction and X-ray photoelectron spectroscopy characterizations affirm that partial Co2+/Co3+ ions in Co3S4 have been substituted by Fe2+/Fe3+ ions to form FeCo2S4. The obtained FeCo2S4@Ni exhibits an ultrahigh specific capacitance (1644.07 mF cm-2 at 50 mA cm-2) and a supreme cycling stability (∼100% after 10,000 cycles at 50 mA cm-2) as binder-free electrodes for supercapacitors. The cycling stability of the fabricated product is the highest among the documented ternary metallic sulfides so far. The excellent supercapacitive performance of FeCo2S4@Ni emanates from the unique architectures of Fe2Co2S4 nanoflower arrays constituted by ultrathin nanoflakes, three-dimensional porous and conductive Ni foam, and solid skeleton of Ni foam for robust connections to the Fe2Co2S4.

Non-Volatile Ferroelectric Switching of Ferromagnetic Resonance in NiFe/PLZT Multiferroic Thin Film Heterostructures.

PubMed

Hu, Zhongqiang; Wang, Xinjun; Nan, Tianxiang; Zhou, Ziyao; Ma, Beihai; Chen, Xiaoqin; Jones, John G; Howe, Brandon M; Brown, Gail J; Gao, Yuan; Lin, Hwaider; Wang, Zhiguang; Guo, Rongdi; Chen, Shuiyuan; Shi, Xiaoling; Shi, Wei; Sun, Hongzhi; Budil, David; Liu, Ming; Sun, Nian X

2016-09-01

Magnetoelectric effect, arising from the interfacial coupling between magnetic and electrical order parameters, has recently emerged as a robust means to electrically manipulate the magnetic properties in multiferroic heterostructures. Challenge remains as finding an energy efficient way to modify the distinct magnetic states in a reliable, reversible, and non-volatile manner. Here we report ferroelectric switching of ferromagnetic resonance in multiferroic bilayers consisting of ultrathin ferromagnetic NiFe and ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films, where the magnetic anisotropy of NiFe can be electrically modified by low voltages. Ferromagnetic resonance measurements confirm that the interfacial charge-mediated magnetoelectric effect is dominant in NiFe/PLZT heterostructures. Non-volatile modification of ferromagnetic resonance field is demonstrated by applying voltage pulses. The ferroelectric switching of magnetic anisotropy exhibits extensive applications in energy-efficient electronic devices such as magnetoelectric random access memories, magnetic field sensors, and tunable radio frequency (RF)/microwave devices.

Non-Volatile Ferroelectric Switching of Ferromagnetic Resonance in NiFe/PLZT Multiferroic Thin Film Heterostructures

PubMed Central

Hu, Zhongqiang; Wang, Xinjun; Nan, Tianxiang; Zhou, Ziyao; Ma, Beihai; Chen, Xiaoqin; Jones, John G.; Howe, Brandon M.; Brown, Gail J.; Gao, Yuan; Lin, Hwaider; Wang, Zhiguang; Guo, Rongdi; Chen, Shuiyuan; Shi, Xiaoling; Shi, Wei; Sun, Hongzhi; Budil, David; Liu, Ming; Sun, Nian X.

2016-01-01

Magnetoelectric effect, arising from the interfacial coupling between magnetic and electrical order parameters, has recently emerged as a robust means to electrically manipulate the magnetic properties in multiferroic heterostructures. Challenge remains as finding an energy efficient way to modify the distinct magnetic states in a reliable, reversible, and non-volatile manner. Here we report ferroelectric switching of ferromagnetic resonance in multiferroic bilayers consisting of ultrathin ferromagnetic NiFe and ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films, where the magnetic anisotropy of NiFe can be electrically modified by low voltages. Ferromagnetic resonance measurements confirm that the interfacial charge-mediated magnetoelectric effect is dominant in NiFe/PLZT heterostructures. Non-volatile modification of ferromagnetic resonance field is demonstrated by applying voltage pulses. The ferroelectric switching of magnetic anisotropy exhibits extensive applications in energy-efficient electronic devices such as magnetoelectric random access memories, magnetic field sensors, and tunable radio frequency (RF)/microwave devices. PMID:27581071

Non-Volatile Ferroelectric Switching of Ferromagnetic Resonance in NiFe/PLZT Multiferroic Thin Film Heterostructures

NASA Astrophysics Data System (ADS)

Hu, Zhongqiang; Wang, Xinjun; Nan, Tianxiang; Zhou, Ziyao; Ma, Beihai; Chen, Xiaoqin; Jones, John G.; Howe, Brandon M.; Brown, Gail J.; Gao, Yuan; Lin, Hwaider; Wang, Zhiguang; Guo, Rongdi; Chen, Shuiyuan; Shi, Xiaoling; Shi, Wei; Sun, Hongzhi; Budil, David; Liu, Ming; Sun, Nian X.

2016-09-01

Magnetoelectric effect, arising from the interfacial coupling between magnetic and electrical order parameters, has recently emerged as a robust means to electrically manipulate the magnetic properties in multiferroic heterostructures. Challenge remains as finding an energy efficient way to modify the distinct magnetic states in a reliable, reversible, and non-volatile manner. Here we report ferroelectric switching of ferromagnetic resonance in multiferroic bilayers consisting of ultrathin ferromagnetic NiFe and ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films, where the magnetic anisotropy of NiFe can be electrically modified by low voltages. Ferromagnetic resonance measurements confirm that the interfacial charge-mediated magnetoelectric effect is dominant in NiFe/PLZT heterostructures. Non-volatile modification of ferromagnetic resonance field is demonstrated by applying voltage pulses. The ferroelectric switching of magnetic anisotropy exhibits extensive applications in energy-efficient electronic devices such as magnetoelectric random access memories, magnetic field sensors, and tunable radio frequency (RF)/microwave devices.

Modeling and characterization of as-welded microstructure of solid solution strengthened Ni-Cr-Fe alloys resistant to ductility-dip cracking part I: Numerical modeling

NASA Astrophysics Data System (ADS)

Unfried-Silgado, Jimy; Ramirez, Antonio J.

2014-03-01

This work aims the numerical modeling and characterization of as-welded microstructure of Ni-Cr-Fe alloys with additions of Nb, Mo and Hf as a key to understand their proven resistance to ductility-dip cracking. Part I deals with as-welded structure modeling, using experimental alloying ranges and Calphad methodology. Model calculates kinetic phase transformations and partitioning of elements during weld solidification using a cooling rate of 100 K.s-1, considering their consequences on solidification mode for each alloy. Calculated structures were compared with experimental observations on as-welded structures, exhibiting good agreement. Numerical calculations estimate an increase by three times of mass fraction of primary carbides precipitation, a substantial reduction of mass fraction of M23C6 precipitates and topologically closed packed phases (TCP), a homogeneously intradendritic distribution, and a slight increase of interdendritic Molybdenum distribution in these alloys. Incidences of metallurgical characteristics of modeled as-welded structures on desirable characteristics of Ni-based alloys resistant to DDC are discussed here.

Origin and tuning of the magnetic anisotropy in Fe2P-based alloys

NASA Astrophysics Data System (ADS)

Zhuravlev, Ivan; Antropov, V. P.; Belashchenko, K. D.

Fe2P-based alloys have been studied for years due to their potential magnetocaloric applications. In addition, Fe2P demonstrates record-high magnetocrystalline anisotropy (MCA) for systems with no heavy elements. While the Curie temperature TC in pure Fe2P is too low for applications, this system appears to be highly tunable, and its TC can be greatly increased by alloying with many other d and p elements. Here we present the electronic structure analysis of magnetic properties of these alloys, searching for systems with higher TC while preserving high MCA. The microscopic origin of the dominant contribution to MCA and its concentration dependence is revealed. We further find that co-alloying with Co or Ni and Si is a promising strategy for achieving high Curie temperature and MCA, which is more favorable compared to individual alloying by Co/Ni or Si due to the compensation of their effects on the band occupation. Work at UNL supported by NSF Grants DMR-1308751 and DMR-1609776. Work at Ames Lab was supported by the Critical Materials Institute, an Energy Innovation Hub funded by the US DOE.

Local Energies and Energy Fluctuations — Applied to the High Entropy Alloy CrFeCoNi

NASA Astrophysics Data System (ADS)

Fukushima, Tetsuya; Katayama-Yoshida, Hiroshi; Sato, Kazunori; Ogura, Masako; Zeller, Rudolf; Dederichs, Peter H.

2017-11-01

High entropy alloys show a variety of fascinating properties like high hardness, wear resistance, corrosion resistance, etc. They are random solid solutions of many components with rather high concentrations. We perform ab-initio calculations for the high entropy alloy CrFeCoNi, which equal concentration of 25% for each element. By the KKRnano program package, which is based on an order-N screened Korringa-Kohn-Rostoker Green's function method, we consider a face-centered cubic (FCC) supercell with 1372 randomly distributed elements, and in addition also smaller supercells with 500 and 256 atoms. It is found from our calculations that the local moments of the Cr atoms show a large environmental variation, ranging from -1.70 μB to +1.01 μB with an average of about -0.51 μB. We present a new method to calculate "local energies" of all atoms. This is based on the partitioning of the whole space into Voronoi cells and allows to calculate the energetic contribution of each atomic cell to the total energy of the supercell. The supercell calculations show very large variations of the local energies, analogous to the variations of the local moments. This shows that the random solid solution is not stable and has a tendency to form an L12-structure with the Cr-atoms ordered at the corner of the cube and the elements Fe, Co, and Ni randomly distributed on the three other FCC sublattices. For this structure the variation of the local moments are much smaller.

Spin fluctuation induced linear magnetoresistance in ultrathin superconducting FeSe films

DOE PAGES

Wang, Qingyan; Zhang, Wenhao; Chen, Weiwei; ...

2017-07-21

The discovery of high-temperature superconductivity in FeSe/STO has trigged great research interest to reveal a range of exotic physical phenomena in this novel material. Here we present a temperature dependent magnetotransport measurement for ultrathin FeSe/STO films with different thickness and protection layers. Remarkably, a surprising linear magnetoresistance (LMR) is observed around the superconducting transition temperatures but absent otherwise. The experimental LMR can be reproduced by magnetotransport calculations based on a model of magnetic field dependent disorder induced by spin fluctuation. Thus, the observed LMR in coexistence with superconductivity provides the first magnetotransport signature for spin fluctuation around the superconducting transitionmore » region in ultrathin FeSe/STO films.« less

Fe-Ni-Cu-C-S phase relations at high pressures and temperatures - The role of sulfur in carbon storage and diamond stability at mid- to deep-upper mantle

NASA Astrophysics Data System (ADS)

Tsuno, Kyusei; Dasgupta, Rajdeep

2015-02-01

Constraining the stable form of carbon in the deep mantle is important because carbon has key influence on mantle processes such as partial melting and element mobility, thereby affecting the efficiency of carbon exchange between the endogenic and exogenic reservoirs. In the reduced, mid- to deep-upper mantle, the chief host of deep carbon is expected to be graphite/diamond but in the presence of Fe-Ni alloy melt in the reduced mantle and owing to high solubility of carbon in such alloy phase, diamond may become unstable. To investigate the nature of stable, C-bearing phases in the reduced, mid- to deep-upper mantle, here we have performed experiments to examine the effect of sulfur on the phase relations of the Ni-rich portion of Fe-Ni ± Cu-C-S system, and carbon solubility in the Fe-Ni solid and Fe-Ni-S liquid alloys at 6-8 GPa and 800-1400 °C using a multianvil press. Low-temperature experiments for six starting mixes (Ni/(Fe + Ni) ∼ 0.61, 8-16 wt.% S) contain C-bearing, solid Fe-Ni alloy + Fe-Ni-C-S alloy melt + metastable graphite, and the solid alloy-out boundary is constrained, at 1150-1200 °C at 6 GPa and 900-1000 °C at 8 GPa for S-poor starting mix, and at 1000-1050 °C at 6 GPa and 900-1000 °C at 8 GPa for the S-rich starting mix. The carbon solubility in the liquid alloy significantly diminishes from 2.1 to 0.8 wt.% with sulfur in the melt increasing from 8 to 24 wt.%, irrespective of temperature. We also observed a slight decrease of carbon solubility in the liquid alloy with increasing pressure when alloy liquid contains >∼18 wt.% S, and with decreasing Ni/(Fe + Ni) ratio from 0.65 to ∼0.53. Based on our results, diamond, coexisting with Ni-rich sulfide liquid alloy is expected to be stable in the reduced, alloy-bearing oceanic mantle with C content as low as 20 to 5 ppm for mantle S varying between 100 and 200 ppm. Deep, reduced root of cratonic mantle, on the other hand, is expected to have C distributed among solid alloy, liquid alloy

Understanding effect of 3.5 wt.% NaCl on the corrosion of Al0.1CoCrFeNi high-entropy alloy

NASA Astrophysics Data System (ADS)

Kumar, N.; Fusco, M.; Komarasamy, M.; Mishra, R. S.; Bourham, M.; Murty, K. L.

2017-11-01

High entropy alloys are a new class of metallic materials with potential for use in a wide variety of applications including their use in corrosive environment. The present study focused on the corrosion behavior of a single-phase, face-centered cubic high entropy alloy (HEA) Al0.1CoCrFeNi in as-cast condition, and the results are compared with the corrosion behavior of the SS304. The microstructural characterization of the alloys in as-received condition was carried out using optical microscopy, electron backscattered diffraction, energy dispersive spectroscopy, and X-ray diffraction. Corrosion behavior was studied using potentiodynamic polarization test in a 3.5 wt% NaCl solution and electrochemical impedance spectroscopy at room temperature. It was observed that the general corrosion resistance of the HEA was better than that of SS304. Pitting potential of the HEA was found to be superior to that of the SS304. Corrosion pits size was slightly smaller in SS304 than that in the HEA. 3D imaging determined that the pit depths were of the same order in both cases. Overall, the HEA Al0.1CoCrFeNi demonstrated a better resistance to general and pitting corrosion.

High-Strength Ultra-Fine-Grained Hypereutectic Al-Si-Fe-X (X = Cr, Mn) Alloys Prepared by Short-Term Mechanical Alloying and Spark Plasma Sintering.

PubMed

Průša, Filip; Bláhová, Markéta; Vojtěch, Dalibor; Kučera, Vojtěch; Bernatiková, Adriana; Kubatík, Tomáš František; Michalcová, Alena

2016-11-30

In this work, Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn (wt %) alloys were prepared by a combination of short-term mechanical alloying and spark plasma sintering. The microstructure was composed of homogeneously dispersed intermetallic particles forming composite-like structures. X-ray diffraction analysis and TEM + EDS analysis determined that the α-Al along with α-Al 15 (Fe,Cr)₃Si₂ or α-Al 15 (Fe,Mn)₃Si₂ phases were present, with dimensions below 130 nm. The highest hardness of 380 ± 7 HV5 was observed for the Al-20Si-10Fe-6Mn alloy, exceeding the hardness of the reference as-cast Al-12Si-1Cu-1 Mg-1Ni alloy (121 ± 2 HV5) by nearly a factor of three. Both of the prepared alloys showed exceptional thermal stability with the hardness remaining almost the same even after 100 h of annealing at 400 °C. Additionally, the compressive strengths of the Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn alloys reached 869 MPa and 887 MPa, respectively, and had virtually the same values of 870 MPa and 865 MPa, respectively, even after 100 h of annealing. More importantly, the alloys showed an increase in ductility at 400 °C, reaching several tens of percent. Thus, both of the investigated alloys showed better mechanical properties, including superior hardness, compressive strength and thermal stability, as compared to the reference Al-10Si-1Cu-1Mg-1Ni alloy, which softened remarkably, reducing its hardness by almost 50% to 63 ± 8 HV5.

High-Strength Ultra-Fine-Grained Hypereutectic Al-Si-Fe-X (X = Cr, Mn) Alloys Prepared by Short-Term Mechanical Alloying and Spark Plasma Sintering

PubMed Central

Průša, Filip; Bláhová, Markéta; Vojtěch, Dalibor; Kučera, Vojtěch; Bernatiková, Adriana; Kubatík, Tomáš František; Michalcová, Alena

2016-01-01

In this work, Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn (wt %) alloys were prepared by a combination of short-term mechanical alloying and spark plasma sintering. The microstructure was composed of homogeneously dispersed intermetallic particles forming composite-like structures. X-ray diffraction analysis and TEM + EDS analysis determined that the α-Al along with α-Al15(Fe,Cr)3Si2 or α-Al15(Fe,Mn)3Si2 phases were present, with dimensions below 130 nm. The highest hardness of 380 ± 7 HV5 was observed for the Al-20Si-10Fe-6Mn alloy, exceeding the hardness of the reference as-cast Al-12Si-1Cu-1 Mg-1Ni alloy (121 ± 2 HV5) by nearly a factor of three. Both of the prepared alloys showed exceptional thermal stability with the hardness remaining almost the same even after 100 h of annealing at 400 °C. Additionally, the compressive strengths of the Al-20Si-10Fe-6Cr and Al-20Si-10Fe-6Mn alloys reached 869 MPa and 887 MPa, respectively, and had virtually the same values of 870 MPa and 865 MPa, respectively, even after 100 h of annealing. More importantly, the alloys showed an increase in ductility at 400 °C, reaching several tens of percent. Thus, both of the investigated alloys showed better mechanical properties, including superior hardness, compressive strength and thermal stability, as compared to the reference Al-10Si-1Cu-1Mg-1Ni alloy, which softened remarkably, reducing its hardness by almost 50% to 63 ± 8 HV5. PMID:28774094

Effect of self-absorption correction on surface hardness estimation of Fe-Cr-Ni alloys via LIBS.

PubMed

Ramezanian, Zahra; Darbani, Seyyed Mohammad Reza; Majd, Abdollah Eslami

2017-08-20

The effect of self-absorption was investigated on the estimation of surface hardness of Fe-Cr-Ni metallic alloys by the laser-induced breakdown spectroscopy (LIBS) technique. For this purpose, the linear relationship between the ratio of chromium ionic to atomic line intensities (CrII/CrI) and surface hardness was studied, both before and after correcting the self-absorption effect. The correlation coefficient significantly increased from 47% to 90% after self-absorption correction. The results showed the measurements of surface hardness using LIBS can be more accurate and valid by correcting the self-absorption effect.

Electrodeposition of Nanocrystalline Ni–Fe Alloy Coatings Based on 1-Butyl-3-Methylimidazolium-Hydrogen Sulfate Ionic Liquid.

PubMed

He, Xinkuai; Zhang, Chuang; Zhu, Qingyun; Lu, Haozi; Cai, Youxing; Wu, Luye

2017-02-01

The electrodeposition of nanocrystalline Ni–Fe alloy coatings and associated nucleation/growth processes are investigated on the glassy carbon (GC) electrode in 1-butyl-3-methylimidazolium-hydrogen sulfate ([BMIM]HSO4) ionic liquid (IL). Cyclic voltammetric data suggest that the co-electrodeposition of Ni–Fe alloys is quasi-reversible. Moreover, chronoamperometry results indicate that the electrodeposition proceeds via a simultaneous nucleation and three-dimensional growth mechanism. In addition, the effects of electrodeposition potential and electrolyte temperature on the coating thickness and Fe content are also studied. The microstructure and composition of the Ni–Fe alloy coatings on Cu substrate are investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). SEM observations show that these electrodeposits present a dense and compact structure, EDS analysis indicates that the coatings are composed of Ni and Fe, XRD pattern shows the coatings are crystalline with a face-centred cubic (fcc) structure. Tafel plots reveal that the Ni–Fe alloy prepared from [BMIM]HSO4 IL presents better corrosion resistance than that of pure Ni.

Integration of Electrodeposited Ni-Fe in MEMS with Low-Temperature Deposition and Etch Processes

PubMed Central

Schiavone, Giuseppe; Murray, Jeremy; Perry, Richard; Mount, Andrew R.; Desmulliez, Marc P. Y.; Walton, Anthony J.

2017-01-01

This article presents a set of low-temperature deposition and etching processes for the integration of electrochemically deposited Ni-Fe alloys in complex magnetic microelectromechanical systems, as Ni-Fe is known to suffer from detrimental stress development when subjected to excessive thermal loads. A selective etch process is reported which enables the copper seed layer used for electrodeposition to be removed while preserving the integrity of Ni-Fe. In addition, a low temperature deposition and surface micromachining process is presented in which silicon dioxide and silicon nitride are used, respectively, as sacrificial material and structural dielectric. The sacrificial layer can be patterned and removed by wet buffered oxide etch or vapour HF etching. The reported methods limit the thermal budget and minimise the stress development in Ni-Fe. This combination of techniques represents an advance towards the reliable integration of Ni-Fe components in complex surface micromachined magnetic MEMS. PMID:28772683

Electronic structure of Fe, Co, and Ni impurities in Pd

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Acker, J.F.; Weijs, P.W.J.; Fuggle, J.C.

1988-11-15

A photoemission study of the valence bands of the dilute alloys PdFe, PdCo, and PdNi is presented. We use the Cooper minimum effect to estimate the local density of states on the impurity site. The behavior of transition-metal impurities in a transition-metal matrix is shown to be very different from their behavior in s-p metals. Our conclusion is that the Fe and Co 3d states are mixed with states throughout the Pd 4d band, while the Ni contribution to the spectra is dominated by a peak of (minority) 3d states near the Fermi level.

Electrodeposited Nanolaminated CoNiFe Cores for Ultracompact DC-DC Power Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J; Kim, M; Herrault, F

2015-09-01

Laminated metallic alloy cores (i.e., alternating layers of thin film metallic alloy and insulating material) of appropriate lamination thickness enable suppression of eddy current losses at high frequencies. Magnetic cores comprised of many such laminations yield substantial overall magnetic volume, thereby enabling high-power operation. Previously, we reported nanolaminated permalloy (Ni-80 Fe-20) cores based on a sequential electrodeposition technique, demonstrating negligible eddy current losses at peak flux densities up to 0.5 T and operating at megahertz frequencies. This paper demonstrates improved performance of nanolaminated cores comprising tens to hundreds of layers of 300-500-nm-thick CoNiFe films that exhibit superior magnetic properties (e.g.,more » higher saturation flux density and lower coercivity) than permalloy. Nanolaminated CoNiFe cores can be operated up to a peak flux density of 0.9 T, demonstrating improved power handling capacity and exhibiting 30% reduced volumetric core loss, attributed to lowered hysteresis losses compared to the nanolaminated permalloy core of the same geometry. Operating these cores in a buck dc-dc power converter at a switching frequency of 1 MHz, the nanolaminated CoNiFe cores achieved a conversion efficiency exceeding 90% at output power levels up to 7 W, compared to an achieved permalloy core conversion efficiency below 86% at 6 W.« less

Crystallization induced ordering of hard magnetic L1{sub 0} phase in melt-spun FeNi-based ribbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sato, Kazuhisa, E-mail: sato@uhvem.osaka-u.ac.jp; Sharma, Parmanand; Zhang, Yan

2016-05-15

The microstructure of newly developed hard magnetic Fe{sub 42}Ni{sub 41.3}Si{sub x}B{sub 12-x}P{sub 4}Cu{sub 0.7} (x = 2 to 8 at%) nanocrystalline alloy ribbons has been studied by transmission electron microscopy (TEM) and electron diffraction. A high-density polycrystalline grains, ∼30 nm in size, were formed in a ribbon after annealing at 673 K for 288 hours. Elemental mapping of the annealed specimen revealed the coexistence of three regions, Fe-rich, Ni-rich, and nearly equiatomic Fe-Ni, with areal fractions of 37%, 40%, and 23 %, respectively. The equiatomic L1{sub 0}-type ordered phase of FeNi was detected in between the Fe and Ni-rich phases.more » The presence of superlattice reflections in nanobeam electron diffraction patterns confirmed the formation of the hard magnetic L1{sub 0} phase beyond any doubt. The L1{sub 0} phase of FeNi was detected in alloys annealed in the temperature range of 673 to 813 K. The present results suggest that the order-disorder transition temperature of L1{sub 0} FeNi is higher than the previously reported value (593 K). The high diffusion rates of the constituent elements induced by the crystallization of an amorphous phase at relatively low temperature (∼673 K) are responsible for the development of atomic ordering in FeNi.« less

Interfacial exchange interactions and magnetism of Ni2MnAl /Fe bilayers

NASA Astrophysics Data System (ADS)

Yanes, R.; Simon, E.; Keller, S.; Nagyfalusi, B.; Khmelevsky, S.; Szunyogh, L.; Nowak, U.

2017-08-01

Based on multiscale calculations combining ab initio methods with spin dynamics simulations, we perform a detailed study of the magnetic behavior of Ni2MnAl /Fe bilayers. Our simulations show that such a bilayer exhibits a small exchange bias effect when the Ni2MnAl Heusler alloy is in a disordered B2 phase. Additionally, we present an effective way to control the magnetic structure of the Ni2MnAl antiferromagnet, in the pseudo-ordered B2-I as well as the disordered B2 phases, via a spin-flop coupling to the Fe layer.

Anomalous magnetotransport behavior in Fe-doped MnNiGe alloys

NASA Astrophysics Data System (ADS)

Dutta, P.; Pramanick, S.; Singh, Vijay; Major, Dan Thomas; Das, D.; Chatterjee, S.

2016-04-01

The electrical dc transport properties of hexagonal magnetic equiatomic alloys of nominal composition Mn1 -xFexNiGe (x =0.2 and0.25 ) have been investigated experimentally as well as theoretically using first-principles electronic structure calculations. Thermal hysteresis in the magnetization data indicates that the alloys undergo a first-order martensitic transition. Both the alloys show unusual nonmetallic resistivity behavior and a noticeable amount of training effect in resistivity when thermally cycled through the first-order martensitic transition. We observe moderate negative magnetoresistance (˜-11.5 % for 150 kOe) at 5 K (well below the martensitic transition temperature) associated with clear virgin line effect for both the alloys. We have adapted different flavors of density functional theory approach to understand the experimentally observed nonmetallic transport behavior.

Effect of fibre laser marking on surface properties and corrosion resistance of a Fe-Ni-Cr alloy

NASA Astrophysics Data System (ADS)

Astarita, Antonello; Mandolfino, Chiara; Lertora, Enrico; Gambaro, Carla; Squillace, Antonino; Scherillo, Fabio

2017-10-01

Fiber laser techniques are increasing their use in many applications, including modification of material surface properties. In particular they are often used for materials' marking as a non-contact processing. In spite of this, the impact of the laser beam on the surface causes metallurgical and morphological changes. The developments during the laser-material interaction can also affect other surface properties, especially corrosion properties which are crucial in the case of Iron-Nickel alloys. Effect of laser marking on a Fe-Cr-Ni alloy using a Tm-fibre laser (IPG Photonics TRL1904; maximum power: 50W, wavelength: 1904 nm), is described in this paper. In order to evaluate the effect of the laser on corrosion properties a specific ageing test in salt spray has been performed. Moreover, superficial morphology analyses have been performed on samples before and after corrosion tests. Possibilities and limitations of laser marking on these alloys have been discussed, in particular from the point of view of the marked surface corrosion resistance preservation.

Nanopatterning of magnetic domains: Fe coverage of self-assembled alumina nanostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Qibin; Wang, Bo -Yao; Lin, Wen -Chin

2015-08-19

Nanosized ultrathin magnetic films were prepared by controlling the deposition of Fe onto an oxidized NiAl(001) surface with an alumina nanostructure on it. Because the ultrathin ferromagnetic Fe films on the bare NiAl(001) surface are separated by paramagnetic Fe nanoparticles on the alumina stripes, as determined by scanning electron microscopy with spin analysis, they form rectangular domains with sizes ranging from tens of nanometer to larger than a micrometer. Furthermore, magnetic domain patterning can thus be achieved by controlling the Fe coverage and nanostructured template.

Growth of Ni-Al alloys on Ni(1 1 1), from Al deposits of various thicknesses: (II) Formation of NiAl over a Ni 3Al interfacial layer

NASA Astrophysics Data System (ADS)

Le Pévédic, S.; Schmaus, D.; Cohen, C.

2007-01-01

This paper describes the second part of a study devoted to the growth of thin Ni-Al alloys after deposition of Al on Ni(1 1 1). In the previous paper [S. Le Pévédic, D. Schmaus, C. Cohen, Surf. Sci. 600 (2006) 565] we have described the results obtained for ultra-thin Al deposits, leading, after annealing at 750 K, to an epitaxial layer of Ni 3Al(1 1 1). In the present paper we show that this regime is only observed for Al deposits smaller than 8 × 10 15 Al/cm 2 and we describe the results obtained for Al deposits exceeding this critical thickness, up to 200 × 10 15 Al/cm 2. Al deposition was performed at low temperature (around 130 K) and the alloying process was followed in situ during subsequent annealing, by Auger electron spectroscopy, low energy electron diffraction and ion beam analysis-channeling measurements, in an ultra-high vacuum chamber connected to a Van de Graaff accelerator. We evidence the formation, after annealing at 750 K, of a crystallographically and chemically well-ordered NiAl(1 1 0) layer (whose thickness depends on the deposited Al amount), over a Ni 3Al "interfacial" layer (whose thickness—about 18 (1 1 1) planes—is independent of the deposited Al amount). The NiAl overlayer is composed of three variants, at 120° from each other in the surface plane, in relation with the respective symmetries of NiAl(1 1 0) and Ni 3Al(1 1 1). The NiAl layer is relaxed (the lattice parameters of cc-B2 NiAl and fcc-L1 2 Ni 3Al differ markedly), and we have determined its epitaxial relationship. In the case of the thickest alloyed layer formed the results concerning the structure of the NiAl layer have been confirmed and refined by ex situ X-ray diffraction and information on its grain size has been obtained by ex situ Atomic Force Microscopy. The kinetics of the alloying process is complex. It corresponds to an heterogeneous growth leading, above the thin Ni 3Al interfacial layer, to a mixture of Al and NiAl over the whole Al film, up to the

First-principles-based kinetic Monte Carlo studies of diffusion of hydrogen in Ni–Al and Ni–Fe binary alloys

DOE PAGES

Tafen, De Nyago

2015-02-14

The diffusion of dilute hydrogen in fcc Ni–Al and Ni–Fe binary alloys was examined using kinetic Monte Carlo method with input kinetic parameters obtained from first-principles density functional theory. The simulation involves the implementation of computationally efficient energy barrier model that describes the configuration dependence of the hydrogen hopping. The predicted hydrogen diffusion coefficients in Ni and Ni 89.4Fe 10.6 are compared well with the available experimental data. In Ni–Al, the model predicts lower hydrogen diffusivity compared to that in Ni. Overall, diffusion prefactors and the effective activation energies of H in Ni–Fe and Ni–Al are concentration dependent of themore » alloying element. Furthermore, the changes in their values are the results of the short-range order (nearest-neighbor) effect on the interstitial diffusion of hydrogen in fcc Ni-based alloys.« less

Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

DOE PAGES

Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; ...

2015-12-09

Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ~1 GPa, excellent ductility (~60–70%) and exceptional fracture toughness (KJIc>200M Pa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening andmore » ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. In conclusion, we further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.« less

Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi

PubMed Central

Zhang, ZiJiao; Mao, M. M.; Wang, Jiangwei; Gludovatz, Bernd; Zhang, Ze; Mao, Scott X.; George, Easo P.; Yu, Qian; Ritchie, Robert O.

2015-01-01

Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼1 GPa, excellent ductility (∼60–70%) and exceptional fracture toughness (KJIc>200 MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip. PMID:26647978

Experimental determination of carbon solubility in Fe-Ni-S melts

NASA Astrophysics Data System (ADS)

Zhang, Zhou; Hastings, Patrick; Von der Handt, Anette; Hirschmann, Marc M.

2018-03-01

To investigate the effect of metal/sulfide and Ni/Fe ratio on the C storage capacity of sulfide melts, we determine carbon solubility in Fe-Ni-S melts with various (Fe + Ni)/S and Ni/Fe via graphite-saturated high-pressure experiments from 2-7 GPa and 1200-1600 °C. Consistent with previous results, C solubility is high (4-6 wt.%) in metal-rich sulfide melts and diminishes with increasing S content. Melts with near M/S = 1 (XS > 0.4) have <0.5 wt.% C in equilibrium with graphite. C solubility is diminished modestly with increased Ni/Fe ratio, but the effect is most pronounced for S-poor melts, and becomes negligible in near-monosulfide compositions. Immiscibility between S-rich and C-rich melts is observed in Ni-poor compositions, but above ∼18 wt.% Ni there is complete miscibility. Because mantle sulfide compositions are expected to have high Ni concentrations, sulfide-carbide immiscibility is unlikely in natural mantle melts. An empirical parameterization of C solubility in Ni-Fe-S melts as a function of S and Ni contents allows estimation of the C storage capacity of sulfide in the mantle. Importantly, as the metal/sulfide (M/S) ratio of the melt increases, C storage increases both because C solubility increases and because the mass fraction of melt is enhanced by addition of metal from surrounding silicates. Under comparatively oxidized conditions where melts are near M/S = 1, as prevails at <250 km depth, bulk C storage is <3 ppm. In the deeper, more reduced mantle where M/S increases, up to 200 ppm C in typical mantle with 200 ± 100 ppm S can be stored in Fe-Ni-S melts. Thus, metal-rich sulfide melts are the principal host of carbon in the deep upper mantle and below. Residual carbon is present either as diamond or, if conditions are highly reduced and total C concentrations are low, solid alloy.

The effect of grain boundary chemistry on Intergranular stress corrosion cracking of Ni-Cr-Fe alloys in 50 Pct NaOH at 140 °C

NASA Astrophysics Data System (ADS)

Sung, J. K.; Koch, J.; Angeliu, T.; Was, G. S.

1992-10-01

The role of chromium, carbon, chromium carbides, and phosphorus on the intergranular stress corrosion cracking (IGSCC) resistance of Ni-Cr-Fe alloys in 50 pct NaOH at 140 °C is studied using controlled-purity alloys. The effect of carbon is studied using heats in which the carbon level is varied between 0.002 and 0.063 wt pct while the Cr level is fixed at 16.8 wt pct. The effect of Cr is studied using alloys with Cr concentrations between 5 and 30 wt pct. The effect of grain boundary Cr and C together is studied by heat-treating the nominal alloy composition of Ni-16Cr-9Fe-0.035C, and the effect of P is studied using a high-purity, P-doped alloy and a carbon-containing, P-doped alloy. Constant extension rate tensile (CERT) results show that the crack depth increases with decreasing alloy Cr content and increasing alloy C content. Crack- ing severity also correlates inversely with thermal treatment time at 700 °C, during which the grain boundary Cr content rises and the grain boundary C content falls. Phosphorus is found to have a slightly beneficial effect on IG cracking susceptibility. Potentiodynamic polarization and potentiostatic current decay experiments confirm that Cr depletion or grain boundary C enhances the dissolution at the grain boundary. Results support a film rupture-anodic dissolution model in which Cr depletion or grain boundary C (independently or additively) enhances dissolution of nickel from the grain boundary region and leads to increased IG cracking.

Use of Industrial Waste (Al-Dross, Red Mud, Mill Scale) as Fluxing Agents in the Sulfurization of Fe-Ni-Cu-Co Alloy by Carbothermic Reduction of Calcium Sulfate

NASA Astrophysics Data System (ADS)

Heo, Jung Ho; Jeong, Eui Hyuk; Nam, Chul Woo; Park, Kyung Ho; Park, Joo Hyun

2018-06-01

The use of industrial waste [mill scale (MS), red mud (RM), Al-dross (AD)] as fluxing agents in the sulfurization of Fe-Ni-Cu-Co alloy to matte (Fe-Ni-Cu-Co-S) by carbothermic reduction of CaSO4 was investigated at 1673 K (1400 °C). The sulfurization efficiency (SE) was 76 (± 2) pct at RM or AD single fluxing. However, SE drastically increased to approximately 89 pct at a `5AD + 5MS' combination, which was equivalent to reagent-grade chemical `5Al2O3 + 5Fe2O3' fluxing (SE = 88 pct). The present results can be used to improve the cost-effective recovery of rare metals (Ni and Co) from deep sea manganese nodules.

Use of Industrial Waste (Al-Dross, Red Mud, Mill Scale) as Fluxing Agents in the Sulfurization of Fe-Ni-Cu-Co Alloy by Carbothermic Reduction of Calcium Sulfate

NASA Astrophysics Data System (ADS)

Heo, Jung Ho; Jeong, Eui Hyuk; Nam, Chul Woo; Park, Kyung Ho; Park, Joo Hyun

2018-03-01

The use of industrial waste [mill scale (MS), red mud (RM), Al-dross (AD)] as fluxing agents in the sulfurization of Fe-Ni-Cu-Co alloy to matte (Fe-Ni-Cu-Co-S) by carbothermic reduction of CaSO4 was investigated at 1673 K (1400 °C). The sulfurization efficiency (SE) was 76 (± 2) pct at RM or AD single fluxing. However, SE drastically increased to approximately 89 pct at a `5AD + 5MS' combination, which was equivalent to reagent-grade chemical `5Al2O3 + 5Fe2O3' fluxing (SE = 88 pct). The present results can be used to improve the cost-effective recovery of rare metals (Ni and Co) from deep sea manganese nodules.

Ultrathin layered double hydroxide nanosheets with Ni(III) active species obtained by exfoliation for highly efficient ethanol electrooxidation.

PubMed

Xu, Liang; Wang, Zhe; Chen, Xu; Qu, Zongkai; Li, Feng; Yang, Wensheng

2018-01-10

The development of non-precious metal electrocatalysts for renewable energy conversion and storage is compelling but greatly challenging due to low activity of the existing catalysts. Herein, the ultrathin NiAl-layered double hydroxide nanosheets (NiAl-LDH-NSs) are prepared by simple liquid-exfoliation of bulk NiAl-LDHs and first used as ethanol electrooxidation catalysts. The ultrathin two-dimensional (2D) structure ensures that the LDH nanosheets expose a greater number of active sites. More importantly, much Ni(III) active species (NiOOH) in the ultrathin nanosheets are formed by the exfoliation process, which play an authentic catalytic role in the ethanol oxidation reaction (EOR). The presence of NiOOH remarkably improves the reactivity and electrical conductivity of LDH nanosheets. These synergistic effects lead to strikingly more than 30 times enhanced EOR activity of NiAl-LDH-NSs compared to bulk NiAl-LDHs. The obtained electrocatalytic activity is also much better than those of most Ni- and LDH-based EOR catalysts reported to date. In addition, the ultrathin NiAl-LDH-NS electrocatalyst also exhibits good long-term stability (maintain 81.8% of the original value after 10000 s). This study not only provides a highly competitive EOR catalyst, but also opens new avenues toward the design of highly efficient electrode materials that have various potential applications in supercapacitor, Ni-MH battery and other electrocatalytic systems.

Ultrathin layered double hydroxide nanosheets with Ni(III) active species obtained by exfoliation for highly efficient ethanol electrooxidation

PubMed Central

Xu, Liang; Wang, Zhe; Chen, Xu; Qu, Zongkai; Li, Feng; Yang, Wensheng

2018-01-01

The development of non-precious metal electrocatalysts for renewable energy conversion and storage is compelling but greatly challenging due to low activity of the existing catalysts. Herein, the ultrathin NiAl-layered double hydroxide nanosheets (NiAl-LDH-NSs) are prepared by simple liquid-exfoliation of bulk NiAl-LDHs and first used as ethanol electrooxidation catalysts. The ultrathin two-dimensional (2D) structure ensures that the LDH nanosheets expose a greater number of active sites. More importantly, much Ni(III) active species (NiOOH) in the ultrathin nanosheets are formed by the exfoliation process, which play an authentic catalytic role in the ethanol oxidation reaction (EOR). The presence of NiOOH remarkably improves the reactivity and electrical conductivity of LDH nanosheets. These synergistic effects lead to strikingly more than 30 times enhanced EOR activity of NiAl-LDH-NSs compared to bulk NiAl-LDHs. The obtained electrocatalytic activity is also much better than those of most Ni- and LDH-based EOR catalysts reported to date. In addition, the ultrathin NiAl-LDH-NS electrocatalyst also exhibits good long-term stability (maintain 81.8% of the original value after 10000 s). This study not only provides a highly competitive EOR catalyst, but also opens new avenues toward the design of highly efficient electrode materials that have various potential applications in supercapacitor, Ni-MH battery and other electrocatalytic systems. PMID:29622818

Effect of Pre-straining on the Shape Recovery of Fe-Mn-Si-Cr-Ni Shape Memory Alloys

NASA Astrophysics Data System (ADS)

Maji, Bikas C.; Krishnan, Madangopal; Verma, Amit; Basu, R.; Samajdar, I.; Ray, Ranjit K.

2015-02-01

The effect of pre-straining on the shape recovery behavior of Fe-14Mn-6Si-9Cr-5Ni (wt pct) shape memory alloy (SMA) has been studied. The shape recovery associated with the reverse ɛ martensitic transformation, i.e., ɛ → γ, was characterized by dilatometry using specimens which were pre-strained to different extent (0 to 14 pct). Dilatometric studies revealed that in Fe-Mn-Si-Cr-Ni SMA, the shape recovery takes place in two stages: (i) in the first stage, the unpinned fraction of stress-induced ɛ martensite reverts back to parent phase γ in the temperature regime of 353 K to 653 K (80 °C to 380 °C) and (ii) in the second stage the remaining "pinned" ɛ martensite is unpinned by the decomposition of deformation-induced α' martensite in the temperature range of 743 K to 893 K (470 °C to 620 °C). The amount of recovery in the first stage decreases with pre-strain, whereas it increases in the second stage. The ɛ → γ transformation finish temperature, A f, increases with increase in pre-strain amount, though the reverse transformation start temperature, A S, remains unaffected. Microstructural characterization revealed that the amount of deformation-induced α' martensite depends on the mode of straining and the crystallographic texture of the starting material. The reversion of α' martensite is seen to occur by the precipitation of Fe5Ni3Si2-type intermetallic π-phase within these plates.

Cooling field and ion-beam bombardment effects on exchange bias behavior in NiFe/(Ni,Fe)O bilayers.

PubMed

Lin, K W; Wei, M R; Guo, J Y

2009-03-01

The dependence of the cooling field and the ion-beam bombardment on the exchange bias effects in NiFe/(Ni,Fe)O bilayers were investigated. The positive exchange bias was found in the zero-field-cooled (ZFC) process whereas a negative exchange bias occurred in the FC process. The increased exchange field, H(ex) with increasing (Ni,Fe)O thicknesses indicates the thicker the AF (Ni,Fe)O, the stronger the exchange coupling between the NiFe layer and the (Ni,Fe)O layer. In addition, the dependence of the H(ex) (ZFC vs. FC) on the (Ni,Fe)O thicknesses reflects the competition between the applied magnetic field and the (Ni,Fe)O surface layer exchange coupled to the NiFe layer. Further, an unusual oscillating exchange bias was observed in NiFe/(Ni,Fe)O bilayers that results from the surface of the (Ni,Fe)O layer being bombarded with different Ar-ion energies using End-Hall deposition voltages (V(EH)) from 0 to 150 V. The behavior of the H(ex) and the H(c) with the V(EH) is attributed to the surface spin reorientation that is due to moderate ion-beam bombardment effects on the surface of the (Ni,Fe)O layer. Whether the (Ni,Fe)O antiferromagnetic spins are coupled to the NiFe moments antiferromagnetically or ferromagnetically changes the sign of the exchange bias.

Solid-state reactions during mechanical alloying of ternary Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems: A review

NASA Astrophysics Data System (ADS)

Hadef, Fatma

2016-12-01

The last decade has witnessed an intensive research in the field of nanocrystalline materials due to their enhanced properties. A lot of processing techniques were developed in order to synthesis these novel materials, among them mechanical alloying or high-energy ball milling. In fact, mechanical alloying is one of the most common operations in the processing of solids. It can be used to quickly and easily synthesize a variety of technologically useful materials which are very difficult to manufacture by other techniques. One advantage of MA over many other techniques is that is a solid state technique and consequently problems associated with melting and solidification are bypassed. Special attention is being paid to the synthesis of alloys through reactions mainly occurring in solid state in many metallic ternary Fe-Al-X systems, in order to improve mainly Fe-Al structural and mechanical properties. The results show that nanocrystallization is the common result occurring in all systems during MA process. The aim of this work is to illustrate the uniqueness of MA process to induce phase transformation in metallic Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems.

Hierarchical 3D NiFe2O4@MnO2 core-shell nanosheet arrays on Ni foam for high-performance asymmetric supercapacitors.

PubMed

Zhang, Xinyang; Zhang, Ziqing; Sun, Shuanggan; Sun, Qiushi; Liu, Xiaoyang

2018-02-13

Hierarchical NiFe 2 O 4 @MnO 2 core-shell nanosheet arrays (NSAs) were synthesized on Ni foam as an integrated electrode for supercapacitors, using a facile two-step hydrothermal method followed by calcination treatment. The NiFe 2 O 4 nanosheets were designed as the core and ultrathin MnO 2 nanoflakes as the shell, creating a unique three-dimensional (3D) hierarchical electrode on Ni foam. The composite electrode exhibited remarkable electrochemical performance with a high specific capacitance of 1391 F g -1 at a current density of 2 mA cm -2 and long cycling stability at a high current density of 10 mA cm -2 (only 11.4% loss after 3000 cycles). Additionally, an asymmetric supercapacitor (ASC) device was fabricated with a NiFe 2 O 4 @MnO 2 composite as the positive electrode material and activated carbon (AC) as the negative one. The ASC device exhibited a high energy density (45.2 W h kg -1 ) at a power density of 174 W kg -1 , and an excellent cycling stability over 3000 cycles with 92.5% capacitance retention. The remarkable electrochemical performance demonstrated its great potential as a promising candidate for high-performance supercapacitors.

Effect of NiO spin orientation on the magnetic anisotropy of the Fe film in epitaxially grown Fe/NiO/Ag(001) and Fe/NiO/MgO(001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, W.; Jin, E.; Wu, J.

Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichroism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spin orientation changes from in-plane direction in Fe/NiO/Ag(001) to out-of-plane direction in Fe/NiO/MgO(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy inmore » Fe/NiO/Ag(001) is due to a 90{sup o}-coupling between the in-plane NiO spins and the in-plane Fe spins.« less

Nanocrystalline high-entropy alloy (CoCrFeNiAl 0.3 ) thin-film coating by magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao, Weibing; Lan, Si; Gao, Libo

High-entropy CoCrFeNiAl0.3 alloy thin films were prepared by magnetron sputtering technique. The thin film surface was very smooth and homogeneous. The synchrotron X-ray experiment confirmed that (111) type of texture existed in the thin film, and the structure was face-centered cubic nanocrystals with a minor content of ordered NiAl-type body-centered cubic structures. Interestingly, the elastic modulus of the thin film was nearly the same to the bulk single-crystal counterpart, however, the nanohardness is about four times of the bulk single-crystal counterpart. It was found that the high hardness was due to the formation of nanocrystal structure inside the thin filmsmore » and the preferred growth orientation, which could be promising for applications in micro fabrication and advanced coating technologies.« less

Impact of alloy composition on one-dimensional glide of small dislocation loops in concentrated solid solution alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Shi; Bei, Hongbin; Robertson, Ian M.

2017-06-08

One-dimensional glide of loops during ion irradiation at 773 K in a series of Ni-containing concentrated solid solution alloys has been observed directly during experiments conducted inside a transmission electron microscope. It was found that the frequency of the oscillatory motion of the loop, the loop glide velocity as well as the loop jump distance were dependent on the composition of the alloy and the size of the loop. Loop glide was most common for small loops and occurred more frequently in the less complex alloys, being highest in Ni, then NiCo, NiFe and NiCoFeCr. As a result, no measurablemore » loop glide occurred in the NiCoCr, NiCoFeCrMn and NiCoFeCrPd alloys.« less

Structural, mechanical and magnetic study on galvanostatic electroplated nanocrystalline NiFeP thin films

NASA Astrophysics Data System (ADS)

Kalaivani, A.; Senguttuvan, G.; Kannan, R.

2018-03-01

Nickel based alloys has a huge applications in microelectronics and micro electromechanical systems owing to its superior soft magnetic properties. With the advantages of simplicity, cost-effectiveness and controllable patterning, electroplating processes has been chosen to fabricate thin films in our work. The soft magnetic NiFeP thin film was successfully deposited over the surface of copper plate through galvanostatic electroplating method by applying constant current density of 10 mA cm-2 for a deposition rate for half an hour. The properties of the deposited NiFeP thin films were analyzed by subjecting it into different physio-chemical characterization such as XRD, SEM, EDAX, AFM and VSM. XRD pattern confirms the formation of NiFeP particles and the structural analysis reveals that the NiFeP particles were uniformly deposited over the surface of copper substrate. The surface roughness analysis of the NiFeP films was done using AFM analysis. The magnetic studies and the hardness of the thin film were evaluated from the VSM and hardness test. The NiFeP thin films possess lower coercivity with higher magnetization value of 69. 36 × 10-3 and 431.92 Gauss.

Nucleation and Growth of Tetrataenite (FeNi) in Meteorites

NASA Astrophysics Data System (ADS)

Goldstein, J. I.; Williams, D. B.; Zhang, J.

1992-07-01

should also be given by the alpha/alpha + gamma" and gamma"/alpha + gamma" boundaries of the Fe-Ni phase diagram (Figure 1). However, the Ni content of kamacite and tetrataenite in black plessite, which forms below 400 degrees C, is ~10 wt% in kamacite and ~57 to 60 wt% in tetrataenite, much higher than the values given by the equilibrium phase diagram (3). It has been observed experimentally (4) that the Ni composition of the gamma phase formed by martensite decomposition below 400 degrees C lies along a metastable extension of the high temperature gamma/alpha + gamma phase boundary, Figure 2. Therefore, the FeNi phase formed by alpha(sub)2 decomposition below 400 degrees C has a non-equilibrium Ni content, >50 to 56 wt%. The growth or thickening of the FeNi phase occurs by some combination of interface and diffusion control (3). References: (1) Clarke R. S. and Scott E. R. D. (1980) Amer. Mineral. 65, 624-630. (2) Reuter K. B., Williams D. B., and Goldstein J. I. (1989) Met. Trans. 20A, 719-725. (3) Zhang J., Williams D. B. and Goldstein J. I. (1992) Submitted to Geochim. Cosmochim. Acta. (4) Zhang J., Williams L). B. and Goldstein J. I. (1992) Submitted to Met. Trans. Figure 1, which in the hard copy appears here, is an Fe-Ni phase diagram (2). Figure 2, which in the hard copy appears here, shows measured FeNi composition from heat-treated alloys (4).

Exact ab initio transport coefficients in bcc Fe-X (X=Cr, Cu, Mn, Ni, P, Si) dilute alloys

NASA Astrophysics Data System (ADS)

Messina, Luca; Nastar, Maylise; Garnier, Thomas; Domain, Christophe; Olsson, Pär

2014-09-01

Defect-driven diffusion of impurities is the major phenomenon leading to formation of embrittling nanoscopic precipitates in irradiated reactor pressure vessel (RPV) steels. Diffusion depends strongly on the kinetic correlations that may lead to flux coupling between solute atoms and point defects. In this work, flux coupling phenomena such as solute drag by vacancies and radiation-induced segregation at defect sinks are systematically investigated for six bcc iron-based dilute binary alloys, containing Cr, Cu, Mn, Ni, P, and Si impurities, respectively. First, solute-vacancy interactions and migration energies are obtained by means of ab initio calculations; subsequently, self-consistent mean field theory is employed in order to determine the exact Onsager matrix of the alloys. This innovative multiscale approach provides a more complete treatment of the solute-defect interaction than previous multifrequency models. Solute drag is found to be a widespread phenomenon that occurs systematically in ferritic alloys and is enhanced at low temperatures (as for instance RPV operational temperature), as long as an attractive solute-vacancy interaction is present, and that the kinetic modeling of bcc alloys requires the extension of the interaction shell to the second-nearest neighbors. Drag occurs in all alloys except Fe(Cr); the transition from dragging to nondragging regime takes place for the other alloys around (Cu, Mn, Ni) or above (P, Si) the Curie temperature. As far as only the vacancy-mediated solute migration is concerned, Cr depletion at sinks is foreseen by the model, as opposed to the other impurities which are expected to enrich up to no less than 1000 K. The results of this study confirm the current interpretation of the hardening processes in ferritic-martensitic steels under irradiation.

Ab initio investigation of the surface properties of austenitic Fe-Ni-Cr alloys in aqueous environments

NASA Astrophysics Data System (ADS)

Rák, Zs.; Brenner, D. W.

2017-04-01

The surface energetics of two austenitic stainless steel alloys (Type 304 and 316) and three Ni-based alloys (Alloy 600, 690, and 800) are investigated using theoretical methods within the density functional theory. The relative stability of the low index surfaces display the same trend for all alloys; the most closely packed orientation and the most stable is the (111), followed by the (100) and the (110) surfaces. Calculations on the (111) surfaces using various surface chemical and magnetic configurations reveal that Ni has the tendency to segregate toward the surface and Cr has the tendency to segregate toward the bulk. The magnetic frustration present on the (111) surfaces plays an important role in the observed segregation tendencies of Ni and Cr. The stability of the (111) surfaces in contact with aqueous solution are evaluated as a function of temperature, pH, and concentration of aqueous species. The results indicate that the surface stability of the alloys decrease with temperature and pH, and increase slightly with concentration. Under conditions characteristic to an operating pressurized water reactor, the Ni-based alloy series appears to be of better quality than the stainless steel series with respect to corrosion resistance and release of aqueous species when in contact with aqueous solutions.

Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

NASA Technical Reports Server (NTRS)

Johnson, D. R.; Chen, X. F.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

1995-01-01

Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

Ternary NiFeX as soft biasing film in a magnetoresistive sensor

NASA Astrophysics Data System (ADS)

Chen, Mao-Min; Gharsallah, Neila; Gorman, Grace L.; Latimer, Jacquie

1991-04-01

The properties of NiFeX ternary films (X being Al, Au, Nb, Pd, Pt, Si, and Zr) have been studied for soft-film biasing of the magnetoresistive (MR) trilayer sensor. In general, the addition of the element X into the NiFe alloy film decreases the saturation magnetization Bs and magnetoresistance coefficient of the film, while increasing the film's electrical resistivity ρ. One of the desirable properties of a soft film for biasing is high sheet resistance for minimum current flow. A figure of merit Bsρ that takes into account both the rate of increase in Bs and the rate of decrease in ρ when adding X element was derived to compare the effectiveness of various X elements in reducing the current shunting through the soft-film layer. Using this criterion, NiFeNb and NiFeZr emerge as good soft-film materials having a maximum sheet resistance relative to the MR layer. Other critical properties such as magnetoresistance coefficient, magnetostriction, coercivity, and anisotropy field were also examined and are discussed in this paper.

Computational thermodynamics aided design of novel ferritic alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ying; Chen, Tianyi; Tan, Lizhen