• Korean Journal of Materials Research
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• 제12권11호
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• pp.845-849
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• 2002

Alloys of $Fe_3$Al, $Fe_3$Al-6Cr, $Fe_3$Al-4Cr-1Mo, $Ni_3$Al, and $Ni_3$Al-2.8Cr were oxidized at $1000^{\circ}C$ in air, and the oxide scales formed were studied using XRD. SEM, EPMA, and TEM. The oxide scales that formed on $Fe_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$ containing a small amount of dissolved Fe and Cr ions, whereas those that formed on $Ni_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$, together with a small amount of $NiAl_2$$O_4$, NiO and dissolved Cr ions. For the entire alloys tested, nonadherent oxide scales formed, and voids were inevitably existed at the scale-matrix interface.

• Journal of the Korean Magnetics Society
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• 제25권2호
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• pp.31-38
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• 2015

Recently, a first-principles study led to a prediction that quaternary Heusler compounds, CoFeCrZ (Z = Ga, Ge) are excellent half-metallic ferromagnets. In this study, we investigate the electronic and the magnetic properties at the (001) surfaces of CoFeCrGa and CoFeCrGe by means of the full-potential linearized augmented plane wave (FLAPW) method within generalized gradient approximation. We considered two types of surface termination: CoFe-terminated and CrZ-terminated surfaces, Z being either Ga or Ge. From the calculated total magnetic moments and the local density of states, we found that half-metallicity is not preserved for all the surfaces. But the calculated atomic density of states showed that CrGa-terminated surface of the CoFeCrGa is almost half-metallic. The magnetic moment of the Co, Fe, or Cr atoms at the surface or subsurface layers in each system had very different values.

• Journal of the Korean Magnetics Society
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• 제10권6호
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• pp.269-273
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• 2000

Fe-l7Cr-2M(M=Si, Nb, Mo) alloy powder was prepared by plasma electrode rotating atomizer and than the alloy powder was formed and sintered. The particle shape of the Fe-l7Cr-2M(M=Si, Nb, Mo) alloy power is spherical. The saturation magnetization of the sintered Fe-17Cr-2Mo and Fe-l7Cr-2Nb alloy are 155 emu/g. The saturation magnetization of the sintered Fe-l7Cr-2Si alloy is less than that of the sintered Fe-l7Cr-2Mo and Fe-l7Cr-2Nb alloy. The amplitude relative permeability of the sintered Fe-l7Cr-2M(M=Si, Nb, Mo) alloy has the maximum value in the range of 3∼5 Oe applied field at forming pressure 12 ton/cm$^2$, sintering temperature 1200$^{\circ}C$, and frequency 1 kHz. Power loss of the sintered Fe-l7Cr-2Nb alloy is 40 mW/cc at applied field, H$\sub$a/=5 Oe, and frequency, f=1 kHz. The power loss of the sintered Fe-l7Cr-2Nb alloy is a half of that of the sintered Fe-l7Cr-2Si and Fe-l7Cr-2Mo alloy.

• Journal of the Korean institute of surface engineering
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• 제45권2호
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• pp.61-69
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• 2012

Alloys of Fe-(5, 10, 15)Al and Fe-(10, 20, 30, 40)Cr were corroded at 700 and $800^{\circ}C$ for 70 hr in either atmospheric air or 1 atm of Ar+$1%SO_2$ gases. In these atmospheres, Fe-5Al and Fe-10Cr alloys displayed poor corrosion resistance. In atmospheric air, Fe-5Al alloys formed oxide nodules, while Fe-10Cr alloys formed thick scales and internal oxides. In Ar+$1%SO_2$ gases, Fe-5Al and Fe-10Cr alloys formed thick, nonadherent bi-layered scales, which grew primarily by the outward diffusion of Fe ions and inward diffusion of oxygen and sulfur ions. By contrast, in atmospheric air and Ar+$1%SO_2$ gases, Fe-(10, 15)Al and Fe-(20, 30, 40)Cr alloys displayed good corrosion resistance by forming $Al_2O_3$ and $Cr_2O_3$ layers on the surface, respectively.

• Journal of the Korean institute of surface engineering
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• 제22권1호
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• pp.10-16
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• 1989

The properties of carburization on Fe-Cr alloys at 900-96$0^{\circ}C$were investiged. The study on carbide layer which had developed during solid-carburizing was made by use of S.E.M, E.PM.A, and X-ray analyzer. The results obtained were summarized as follows, the composition of carbide and the value of activation energy for the growth of carbide layer on each Fe-Cr alloy were 1) Fe-1Cr : M3C and 52Kcal/mole 2) Fe-3Cr and Fe-5Cr : M7C3and 85-88Kcal/mole 3) Fe-7Cr and Fe-9Cr : (M7C3+M23C6)and 55-66Kcal/mole.

• Applied Microscopy
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• 제45권1호
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• pp.9-15
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• 2015

In the present study, microstructural evolution in CuCrFeNi, CuCrFeNiMn, and CuCrFeNiMnAl alloys has been investigated. The as-cast CuCrFeNi alloy consists of a single fcc phase with the lattice parameter of 0.358 nm, while the as-cast CuCrFeNiMn alloy consists of (bcc+fcc1+fcc2) phases with lattice parameters of 0.287 nm, 0.366 nm, and 0.361 nm. The heat treatment of the cast CuCrFeNiMn alloy results in the different type of microstructure depending on the heat treatment temperature. At $900^{\circ}C$ a new thermodynamically stable phase appears instead of the bcc solid solution phase, while at $1,000^{\circ}C$, the heat treated microstructure is almost same as that in the as-cast state. The addition of Al in CuCrFeNiMn alloy changes the constituent phases from (fcc1+fcc2+bcc) to (bcc1+bcc2).

• Korean Journal of Materials Research
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• 제7권10호
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• pp.898-907
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• 1997

Fe-22Cr-5AI-X(X=Zr, Y)합금을 1143K, 고온 황화(P$s_{2}$=1.11x$10^{-7}$atm, P$O_{s}$ =3.11x$10^{-20atm}$) 및 황화/산화 (P$s_{2}$=8.31x$10^{-8}$atm, P$O_{s}$ =3.31x$10^{-18atm}$) 환경의 복합가스 분위기에서 1-30시간동안 노출하여 합금표면에 형성된 부식층을 관찰하여 SEM/EDS로 분석하였다. Fe-22Cr-5AI합금은 고온 부식환경에서 부식 생성물의 성장은 포물선법칙을 따르고 주요 성분은 결함이 많고 다공질인 철과 크롬의 황화물[(Fe, Cr)Sx]이므로 고온 내식성이 감소하였다. Zr을 1wt%첨가한 Fe-22Cr-5AI합금의 고온 부식거동은 Y을 1wt%첨가한 합금과 비슷한 거동을 나타내었다. 황화환경에서는 Cr의 선택 황화에 의한 크롬 황화물(CrS)이 생성되고 노출시간의 경과에 따라 (Fe, Cr)Sx나 (Cr, Fe)Sx 등의 황화물의 성장으로 고온 내식성이 감소하였다. 그러나 황화/산화환경에서는 초기에는 알루미늄산화물(A $I_{2}$ $O_{3}$)및 지르코늄산화물(Zr $O_{2}$)등이 생성되어 보호적이었으나 15시간이후 부터 (Fe, Cr)Sx나 (Cr, Fe)Sx 의 황화물의 성장으로 고온 내식성이 감소하였다.

• Corrosion Science and Technology
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• 제12권4호
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• pp.163-170
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• 2013

In NaCl solutions acidified with $H_2SO_4$, Fe20Cr1.1N alloy showed enhanced pitting corrosion resistance than Fe20Cr alloy. An XPS analysis revealed that the passive film of Fe20Cr1.1N alloy contained higher cationfraction of Cr than that of Fe20Cr alloy, and nitrogen was incorporated into the film. In addition, it was found that the passive film of Fe20Cr1.1N alloy was thinner and had higher oxygen vacancy density than that of Fe20Cr alloy. Based on these observations, it was concluded that the chemical composition was the determining factor for the protectiveness of the passive film of Fe20Cr based alloy in dilute $H_2SO_4$ solution.

• Journal of Korea Foundry Society
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• 제25권3호
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• pp.128-133
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• 2005

The effects of Mn and Cr on the crystallization behaviors of Fe-bearing intennetallics in A356 alloy were studied. Coarse and acicular ${\beta}-Al_{5}$FeSi phase in A356-0.20wt.%Fe alloy was modified into small ${\alpha}$-Al(Fe,Mn)Si and ${\alpha}$-Al(Fe,Cr)Si phases in response to Mn and Cr addition, respectively. Increasing of Mn addition amount elevates the crystallizing temperature of ${\alpha}$-Al(Fe,Mn)Si and the Mn/Fe ratio in the ${\alpha}$-Al(Fe,Mn)Si. Cr is more effective to modify ${\beta}-Al_{5}$FeSi in comparison with Mn. ${\alpha}$-Al(Fe,Mn)Si phase had BCC/SC dual structure.

• Proceedings of the Korean Magnestics Society Conference
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.194-195
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• 2002

Fe/Cr/Fe trilayers have attracted much interest from both theoretical and experimental aspects due to many novel magnetic properties such as antiferromagnetic coupling, giant magnetoresistance, oscillatory bilinear and biquadratic coupling [1]. In this work, we report that there is an oscillation of magnetic anisotropy with increasing intervening Cr layer thickness in Fe/Cr/Fe trilayers. (omitted)