The evolution of magnetic order in CrFe alloys. II. Onset of ferromagnetism

Burke, S. K.; Cywiński, R.; Davis, John R.; Rainford, B.D.

doi:10.1088/0305-4608/13/2/020

Cited by 159 publications

(67 citation statements)

References 27 publications

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“…For intermediate milling times (between 12 and 24 h), the hyperfine structure is consistent with an hyperfine field distribution streched towards low fields, that is attributed to the diffusion of Cr atoms to the Fe nearest neighbourhood, the high field component due to the substitution of the Fe atoms by Co. After 48 h of milling, one can distinguish the existence of three main Fe environments from the P(H) curve (as it is shown in Fig. 2): (i) a Cr-rich environment containing more than 70 at% Cr [6], which corresponds to the paramagnetic component (zone I), (ii) an Fe-rich environment which is preponderant (72%) and has an average hyperfine field of about 25 T (zone II), and (iii) a Co-rich environment (zone III) having an average hyperfine field H = 35 T similar to those obtained by Eymery et al on a disordered Fe 50 Co 50 rapidly quenched [7]. These environments can be considered as pseudo-binary alloys: Cr-rich (Fe,Co)-Cr, Ferich (Fe,Co)-Cr and Co-rich (Fe,Cr)-Co, respectively.…”

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confidence: 70%

“…It thus results from a random distribution of Cr and Co atoms at near-neighbour sites of 57 Fe nuclei. Indeed, the presence of one Cr atom in the first and second neighbouring shells of Fe atoms decreases the Fe hyperfine field by about 3 and 2.2 T, respectively [5], while the presence of one Co atom as first and second nearest neighbour to Fe atoms increases the hyperfine field by about 0.8 and 0.6 T, respectively [6]. After 6 h of milling, a paramagnetic component with an isomer shift of about --0.12 mm/s is observed, suggesting Fe atoms surrounded by Cr atoms as first and second nearest neighbours: it can be thus attributed to Cr-rich clusters resulting from the diffusion of Fe atoms into Cr matrix.…”

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confidence: 99%

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M�ssbauer Study of Mechanically Alloyed Fe57Cr31Co12

Bentayeb¹,

Alleg²,

Bouzabata³

et al. 2002

phys. stat. sol. (a)

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Subject classification: 75.50.Tt; 76.80.+y; S1.1; S1.2 Nanostructured powders of Fe 57 Cr 31 Co 12 were prepared by mechanical alloying from elemental Fe, Cr and Co powders, using a planetary ball mill type Fritsch Pulverisette 7. The powders were characterized by X-ray diffraction and 57 Fe Mö ssbauer spectrometry. A detailed analysis of the diffraction patterns reveals a decrease of the crystalline grain size as a function of milling time. For the first hours of milling, Mö ssbauer spectra are composed of a magnetic contribution and a single line. The paramagnetic component, whose relative area increases with milling time, can be attributed to paramagnetic Cr-rich clusters. The results are compared to those obtained on the same alloy prepared by conventional melting technique.

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confidence: 70%

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confidence: 99%

M�ssbauer Study of Mechanically Alloyed Fe57Cr31Co12

Bentayeb¹,

Alleg²,

Bouzabata³

et al. 2002

phys. stat. sol. (a)

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“…Iron and chromium are typical examples of a ferromagnet and an antiferromagnet, respectively. As a function of composition and structure the magnetic properties of Fe-Cr vary considerably; e.g., spin glass [3] and giant magnetoresistance [4] features are found in these systems.…”

Section: Introductionmentioning

confidence: 99%

Segregation, precipitation, andα−α′phase separation in Fe-Cr alloys

et al. 2015

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Iron-chromium alloys, the base components of various stainless steel grades, have numerous technologically and scientifically interesting properties. However, these features are not yet sufficiently understood to allow their full exploitation in technological applications. In this work, we investigate segregation, precipitation, and phase separation in Fe-Cr systems analyzing the physical mechanisms behind the observed phenomena. To get a comprehensive picture of Fe-Cr alloys as a function of composition, temperature, and time the present investigation combines Monte Carlo simulations using semiempirical interatomic potential, first-principles total energy calculations, and experimental spectroscopy. In order to obtain a general picture of the relation of the atomic interactions and properties of Fe-Cr alloys in bulk, surface, and interface regions several complementary methods have to be used. Using the exact muffin-tin orbitals method with the coherent potential approximation (CPA-EMTO) the effective chemical potential as a function of Cr content (0-15 at. % Cr) is calculated for a surface, second atomic layer, and bulk. At ∼10 at. % Cr in the alloy the reversal of the driving force of a Cr atom to occupy either bulk or surface sites is obtained. The Cr-containing surfaces are expected when the Cr content exceeds ∼10 at. %. The second atomic layer forms about a 0.3 eV barrier for the migration of Cr atoms between the bulk and surface atomic layer. To get information on Fe-Cr in larger scales we use semiempirical methods. However, for Cr concentration regions less than 10 at. %, the ab initio (CPA-EMTO) result of the important role of the second atomic layer to the surface is not reproducible from the large-scale Monte Carlo molecular dynamics (MCMD) simulation. On the other hand, for the nominal concentration of Cr larger than 10 at. % the MCMD simulations show the precipitation of Cr into isolated pockets in bulk Fe-Cr and the existence of the upper limit of the solubility of Cr into Fe layers in Fe/Cr layer systems. For high Cr concentration alloys the performed spectroscopic measurements support the MCMD simulations. Hard x-ray photoelectron spectroscopy and Auger electron spectroscopy investigations were carried out to explore Cr segregation and precipitation in the Fe/Cr double layer and Fe 0.95 Cr 0.05 and Fe 0.85 Cr 0.15 alloys. Initial oxidation of Fe-Cr was investigated experimentally at 10 −8 Torr pressure of the spectrometers showing intense Cr 2 O 3 signal. Cr segregation and the formation of Cr-rich precipitates were traced by analyzing the experimental atomic concentrations and chemical shifts with respect to annealing time, Cr content, and kinetic energy of the exited electron.

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“…Such plate like phases are expected to be interconnected due to the higher volume fraction in (30-48) % Cr alloys and act as the pinning sites for the domain wall motion to enhance the magnetic hardening in high Cr alloys. The Cr-rich α' phase is poorly magnetic, which transformed to nonmagnetic after changing the alloy composition (80-90% Cr) [16]. Therefore, an increase in volume fraction of the Cr-rich α' phase resulted in a decrease in remanence and maximum induction of the alloys shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of Embrittlement in Isochronal Aged Fe-Cr Alloys by Magnetic Hysteresis Loop Technique

Mohapatra¹,

Kamada²,

Kikuchi³

et al. 2011

Journal of Magnetics

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Fe-Cr alloys with different Cr contents were prepared by an arc melting technique. The alloys were isochronally aged in the range from 400 o C to 900 o C with 50 o C steps with a holding time of 100 hours. The ageing produced embrittlement in the alloys due to either the formation of a Cr-rich α' phase or a σ phase at high temperatures. Magnetic Hysteresis Loop (MHL) and Micro-Vickers hardness were measured at each step to correlate the magnetic and mechanical properties. Coercivity and hardness of the alloys were increased and remanence decreased up to 500-550 o C due to formation of a Cr-rich α' phase. Beyond 500-550 o C range, the coercivity and hardness decreased and remanence increased due to the coarsening or dissolution of the Cr-rich α' phase. In the Fe-48% Cr alloy, formation of the σ phase at 700 o C reduced the maximum induction of the alloy significantly.

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The evolution of magnetic order in CrFe alloys. II. Onset of ferromagnetism

Cited by 159 publications

References 27 publications

M�ssbauer Study of Mechanically Alloyed Fe57Cr31Co12

M�ssbauer Study of Mechanically Alloyed Fe57Cr31Co12

Segregation, precipitation, andα−α′phase separation in Fe-Cr alloys

Evaluation of Embrittlement in Isochronal Aged Fe-Cr Alloys by Magnetic Hysteresis Loop Technique

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