• 한국자기학회지
• /
• 제15권4호
• /
• pp.241-245
• /
• 2005

CoFeNi 합금은 HDD, MEMS 분야에서 head core 재료로 쓰이는 permalloy(FeNi)합금보다 뛰어난 우수한 자기적 특성을 가진 재료로써 최근 많이 연구되어지고 있다. CoFeNi 합금의 조성과 전기도금 시 전류조건에 따른 미세구조와 결정학적 특성이 자기 특성에 미치는 영향을 조사하였으며, 높은 포화자화와 낮은 보자력을 갖는 CoFeNi 삼원계 합금을 전기도금 방식으로 제조하는데 성공하였다. 포화자화 1.9 T, 보자력 0.16 A/m를 갖는 대표적인 CoFeNi film의 조성은 $Co_{30}\;Fe_{34}\;Ni_{36}(at\%)$이며, 미세결정립과 ffc-bcc 상의 혼재가 낮은 보자력을 갖는 요인임을 XRD, TEM의 결과로부터 확인 하였다.

• 한국분말재료학회지
• /
• 제27권1호
• /
• pp.1-7
• /
• 2020

In this research, a new medium-entropy alloy with an equiatomic composition of FeCuNi was designed using a phase diagram (CALPHAD) technique. The FeCuNi MEA was produced from pure iron, copper, and nickel powders through mechanical alloying. The alloy powders were consolidated via a high-pressure torsion process to obtain a rigid bulk specimen. Subsequently, annealing treatment at different conditions was conducted on the four turn HPT-processed specimen. The microstructural analysis indicates that an ultrafine-grained microstructure is achieved after post-HPT annealing, and microstructural evolutions at various stages of processing were consistent with the thermodynamic calculations. The results indicate that the post-HPT-annealed microstructure consists of a dual-phase structure with two FCC phases: one rich in Cu and the other rich in Fe and Ni. The kernel average misorientation value decreases with the increase in the annealing time and temperature, indicating the recovery of HPT-induced dislocations.

• 한국표면공학회지
• /
• 제30권1호
• /
• pp.3-12
• /
• 1997

The composition, the preferred orientation and the magnetic properties of the CoFeCu alloys electrodepositen under various electrolysis conditions in sulfate baths ware investigated. As the D.C. current density increased, the Co content in alloy electrodeposits increased, while the Cu content decreased and Fe content remained content. The effect of magnetic field up to 300 Oe on the composition of alloys was negligible. The Cu content of the alloys deposited in pulse current increased noticeably with increasing off-time, while the Co and Fe content decreased. The coercivity of the alloys with 3.5 to 7.0wt.% Cu was 1.0 to 2.0 Oe, but increased noticeably above and below that composition. The application of magnetic field during deposition decreased the coercivity of alloys. The saturation flux density of the alloys with 3.5 to 5.0wt.% Cu was relatively high in the range from 16 to 20.7Gauss. The anisotropy field(HK) of the alloys deposited under the magnetic field(50∼300 Oe) ranged from 18 to 22 Oe. The alloys had fcc structure with (111) preferred orientation, whose distribution increased a little with increasing magnetic field.

• 한국수소및신에너지학회논문집
• /
• 제9권3호
• /
• pp.111-118
• /
• 1998

The intrinsic degradation behavior of $(V_{0.53}Ti_{0.47})_{0.925}Fe_{0.075}$ alloy with BCC structure and the two plateau regions (the low and high plateau region) has been investigate during the temperature-induced hydrogen absorption-desorption cycling (thermal cycling). After 400 thermal cycles between room temperature and $600^{\circ}C$ under 10atm $H_2$, the total reversible hydrogen absorption capacity decreased by about 40%. From thermal desorption analysis it was found that the degradation behavior at each plateau region was different. In addition, XRD analysis showed that the crystal structure of the sample in de-hydrided state was changed from BCC to BCT after degradation, and that of the sample in hydrided state it was maintained as FCC although peaks were broadened after degradation. From the result of static isothermal hydrogenation treatment it were found that crystal structure change from BCC to BCT was caused by the thermal energy. TEM analysis showed that the peak broadening was due to the formation of an amorphous phase in FCC matrix.

• 한국분말재료학회지
• /
• 제9권5호
• /
• pp.359-364
• /
• 2002

We report the structure, thermal and magnetic properties of a non-equilibrium $Al_{0.6}(Fe_{50}Cu_{50})_{0.4}$ alloy powder produced by rod milling and chemical leaching. An X-ray diffractometry(XRD), a transmission electron microscope(TEM), a differential scanning calorimeter(DSC), a vibrating sample magnetometer(VSM), and superconducting quantum interference device(SQUID) were utilized to characterize the as-milled and leaching specimens. The crystallite size reached a value of about 8.82 nm. In the DSC experiment, the peak temperatures and crystallization temperatures decreased with increasing milling time. The activation energy of crystallization is 200.5 kJ/mole for as-milled alloy powder. The intensities of the XRD peaks of as-milled powders associated with the bcc type $Al_{0.5}Fe_{0.5}$ structure formative at $350^{\circ}C$ sharply increase with increasing annealing temperature. Above $400^{\circ}C$, peaks alloted to $Al_{0.5}Fe_{0.5}$ and $Al_{5}Fe_{2}$ are observed. After annealing at $600^{\circ}C$ for 1h, the leached Ll specimen transformed into bcc $\alpha$-Fe and fcc Cu phases, accompanied by a change in the structural and magnetic properties. The saturation magnetization decreased with increasing milling time, and a value of about 8.42 emu/g was reached at 500 h of milling. The coercivity reached a maximum value of about 142.7 Oe after 500 h of milling. The magnetization of leached specimens as function of fields were higher at 5 K, and increased more sharply at 5 K than at 100 K.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2013년도 임시총회 및 하계학술연구발표회
• /
• pp.15-16
• /
• 2013

Magnetization behavior of ultra thin $Fe_xCo_{1-x}$ alloy (where x varies from 0 to 100) has been investigated as functions of composition on Cr (100) substrate by using in situ surface magneto optical Kerr effect (SMOKE). It's always show in plane uniaxial magnetic anisotropy at room temperature (RT) & Low temperature (LT). It is observed that composition dependent coercive force maximum at about 30 at % Co and 70 at % Co atomic ratio and minimum near equiatomic site. The relative magnetic moments as composition variation also show magnetization collapse near equiatomic site. The magnetization behaviors of Fe-Co alloy on Cr (100) due to composition varies are supported the order-disordering as well as structural stability bcc (ferromagnetic)/fcc (anti-ferromagnetic) phase stability magnetism.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
• /
• pp.29-29
• /
• 1999

The synthesis of layered structures on the nanometer scale has become essential for continued improvements in the operation of various electronic and magnetic devices. Abrupt metal-metal interfaces are desired for applications ranging from metallization in semiconductor devices to fabrication of magnetoresistive tunnel junctions for read heads on magnetic disk drives. In particular, characterizing the interface structure between various transition metals (TM) and aluminum is desirable. We have used the techniques of MeV ion backscattering and channeling (HEIS), x-ray photoemission (ZPS), x-ray photoelectron diffraction(XPD), low-energy ion scattering (LEIS), and low-energy electron diffraction(LEED), together with computer simulations using embedded atom potentials, to study solid-solid interface structure for thin films of Ni, Fe, Co, Pd, Ti, and Ag on Al(001), Al(110) and Al(111) surfaces. Considerations of lattice matching, surface energies, or compound formation energies alone do not adequately predict our result, We find that those metals with metallic radii smaller than Al(e.g. Ni, Fe, Co, Pd) tend to form alloys at the TM-Al interface, while those atoms with larger atomic radii(e.g. Ti, Ag) form epitaxial overlayers. Thus we are led to consider models in which the strain energy associated with alloy formation becomes a kinetic barrier to alloying. Furthermore, we observe the formation of metastable fcc Ti up to a critical thickness of 5 monolayers on Al(001) and Al(110). For Ag films we observe arbitrarily thick epitaxial growth exceeding 30 monolayers with some Al alloying at the interface, possible driven by interface strain relief. Typical examples of these interface structures will be discussed.

• Interaction and multiscale mechanics
• /
• 제2권1호
• /
• pp.45-68
• /
• 2009

An aim of the study is to develop an efficient numerical simulation technique that can handle the two-scale analysis of fluid permeation filters fabricated by the partial sintering technique of small spherical ceramics. A solid-fluid mixture homogenization method is introduced to predict the mechanical characters such as rigidity and permeability of the porous ceramic filters from the micro-scale geometry and configuration of partially-sintered particles. An extended finite element (X-FE) discretization technique based on the enriched interpolations of respective characteristic functions at fluid-solid interfaces is proposed for the non-interface-fitted mesh solution of the micro-scale analysis that needs non-slip condition at the interface between solid and fluid phases of the unit cell. The homogenization and localization performances of the proposed method are shown in a typical two-dimensional benchmark problem whose model has a hole in center. Three-dimensional applications to the body-centered cubic (BCC) and face-centered cubic (FCC) unit cell models are also shown in the paper. The 3D application is prepared toward the computer-aided optimal design of ceramic filters. The accuracy and stability of the X-FEM based method are comparable to those of the standard interface-fitted FEM, and are superior to those of the voxel type FEM that is often used in such complex micro geometry cases.

• 한국안전학회지
• /
• 제30권4호
• /
• pp.8-13
• /
• 2015

The magnetic shape memory alloys have recently received a lot of attention due to the considerable progress achieved in understanding the particular importance and the development of the factors. Among these alloys, the ferromagnetic Co-Ni- alloys have been concerned specially because of the thermoelastic character of the fcc (g) - bct (a) martensitic transformation which exhibits under the action of the temperature (shape memory effect), the stress (superelasticity) and the magnetic field (magnetoelasticity). The morphological, the crystallographical, and the thermal characteristics of thermally induced martensite in Co-35.3Ni-11.3Al(wt.%) and Co-28.1Ni-47.4Fe-3.3Ti (wt.%) alloy have been investigated by the scanning electron microscope (SEM), the X-ray Diffraction (XRD), and the differential scanning calorimeter (DSC).

• 열처리공학회지
• /
• 제17권6호
• /
• pp.346-355
• /
• 2004

The flame quenching process has been employed to modify the surfaces of commercial marine propeller material, aluminum bronze alloy (Cu-8.8Al-5Ni-5Fe), and the microstructure, hardness and wear properties of the flame-quenched layers have been studied. The thermal history was accurately monitored during the process with respect to both the designed maximum surface temperature and holding time. The XRD and EDX analyses have shown that at temperatures above $T_{\beta}$, the microstructure consisting of ${\alpha}+{\kappa}$ phases changed into the ${\alpha}+{\beta}^{\prime}$ martensite due to an eutectoid reaction of ${\alpha}+{\kappa}{\rightarrow}{\beta}$ and a martensitic transformation of ${\beta}{\rightarrow}{\beta}^{\prime}$. The ${\beta}^{\prime}$ martensite phase formed showed a face-centered cubic (FCC) crystal structure with the typical twinned structure. The hardness of the flame-quenched layer having the ${\alpha}+{\beta}^{\prime}$ structure was similar to that of the ${\alpha}+{\kappa}$ structure and depended sensitively on the size and distribution of hard ${\kappa}$ and ${\beta}^{\prime}$ phases with depth from the surface. As a result of the sliding wear test, the wear resistance of the flame-quenched layer was markedly enhanced with the formation of the ${\beta}^{\prime}$ martensite.