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      • KCI등재

        Characteristic of Microstructure and Mechanical Properties in Ni-Al-Ti Alloy System

        한창석,C. H. Bae,J. H. Lee 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.6

        A transmission electron microscope (TEM) investigation was performed on the microstructural variations and hardness changes in a Ni-Al-Ti alloy system. The hardness after a solution treatment is high in NiAl- and NiTi-base alloys, suggesting a large contribution of solid solution strengthening in this alloy system. TEM observations revealed that spinodal and binodal types of decomposition occur depending on the chemical composition and aging temperature. However, the degree of age hardening is not large compared to the considerable microstructural variation. The temperature dependence of the compressive yield strength of various NiAl-containing morphologies of Ni2AlTi was also investigated. A transmission electron microscope (TEM) investigation was performed on the microstructural variations and hardness changes in a Ni-Al-Ti alloy system. The hardness after a solution treatment is high in NiAl- and NiTi-base alloys, suggesting a large contribution of solid solution strengthening in this alloy system. TEM observations revealed that spinodal and binodal types of decomposition occur depending on the chemical composition and aging temperature. However, the degree of age hardening is not large compared to the considerable microstructural variation. The temperature dependence of the compressive yield strength of various NiAl-containing morphologies of Ni2AlTi was also investigated.

      • KCI등재

        The Behavior of α-Cr Precipitation on the High Temperature Deformation of B2-Ordered NiAl

        한창석,전창환,한성오 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.2

        Transmission electron microscope investigation has been performed concerning the effect of Cr-precipitation on the mechanical properties of B2-ordered NiAl containing 4 mol.% to 8 mol.% of Cr. By aging at temperatures around 973 K after solution annealing, fine spherical precipitates appeared homogeneously in the NiAl matrix and the alloys hardened appreciably. The selected area electron diffraction patterns have not revealed any additional extra-spots during aging, because the Cr-particles have a cube-cube orientation relationship and keep perfect coherency with the ordered matrix lattice. Dislocations bypass the particles during deformation. Although the dispersion of Cr-particles increases the yield strength of NiAl at intermediate temperature, the strength decreases appreciably at higher temperatures. Atom location by channeling enhanced microanalysis technique has been used to determine the site occupancy of Cr in NiAl. Transmission electron microscope investigation has been performed concerning the effect of Cr-precipitation on the mechanical properties of B2-ordered NiAl containing 4 mol.% to 8 mol.% of Cr. By aging at temperatures around 973 K after solution annealing, fine spherical precipitates appeared homogeneously in the NiAl matrix and the alloys hardened appreciably. The selected area electron diffraction patterns have not revealed any additional extra-spots during aging, because the Cr-particles have a cube-cube orientation relationship and keep perfect coherency with the ordered matrix lattice. Dislocations bypass the particles during deformation. Although the dispersion of Cr-particles increases the yield strength of NiAl at intermediate temperature, the strength decreases appreciably at higher temperatures. Atom location by channeling enhanced microanalysis technique has been used to determine the site occupancy of Cr in NiAl.

      • KCI등재

        Effect of Annealing on the Structural Properties of AlN Thin Films Containing Co Particles

        한창석,Yong Ha Kim 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.1

        This paper describes a new approach for preparing AlN thin films containing various Co contents by usinga two-facing targets type sputtering system. The as-deposited films exhibited a variable nature expectedfrom the AlN-rich phase, as well as an amorphous-like phase, depending on the Co content in the films. The films were annealed isothermally at different temperatures and their microstructure, magnetic proper-ties and resistivity were examined. The saturation magnetization of the as-deposited films was quite smalland almost constant, irrespective of the Co content in the films, because Co was not in the crystallinestate. At elevated annealing temperatures, the as-deposited AlN-Co amorphous films crystallized into twophases of AlN and Co. The saturation magnetization and resistivity of the films increased with increasingannealing time and temperature. The coercivity of the films was independent of the annealing time, but itincreased with increasing annealing temperature due to the increase in grain size. A saturation magnetiza-tion, coercivity and resistivity of 360 emu/cm3, ~25 Oe and 2200 µΩ-cm, respectively, were obtained. Fur-ther improvement in the soft magnetic properties might lead to this material being applied as a highdensity magnetic recording head material.

      • KCI등재

        Microstructure and Strength of B2-ordered (Ni,Co)Al

        한창석 대한금속·재료학회 2008 METALS AND MATERIALS International Vol.14 No.3

        A transmission electron microscopy (TEM) investigation of the morphologies and crystal structures of precipitates in supersaturated B2-ordered (Ni,Co)Al has revealed that rod-like precipitates of the (Ni,Co)₂Al phase with a hexagonal structure form parallel to the <111> direction of the B2 matrix. By aging at temperatures below 973 K, a long period superlattice structure of hexagonal (Ni,Co)₂Al was formed. The (Ni,Co)Al hardens appreciably by the precipitation of these phases. An energy dispersive spectroscopy (EDS) was used to analyze the compositions of each phase formed in the B2-(Ni,Co)Al. The effects of the dispersion of the (Ni,Co)₂Al phase on the temperature dependence of the strength of the B2-(Ni,Co)Al have been investigated over a temperature range from 298 K to 1173 K.

      • KCI등재

        무전해 코발트계 석출막에 미치는 기판의 영향

        한창석,천창환,한승오,Han, Chang-Suk,Chun, Chang-Hwan,Han, Seung-Oh 한국재료학회 2009 한국재료학회지 Vol.19 No.6

        The deposition behavior and structural and magnetic properties of electroless Co-B and Co-Fe-B deposits, as well as the amorphous ribbon substrates, were investigated. These Co-based alloy deposits exhibited characteristic polycrystalline structures and surface morphology and magnetic properties that were dependent on the type of amorphous substrates. The catalytic activity sequence of the amorphous ribbon electrodes for anodic oxidation of DMAB was estimated from the current density-potential curve in the anodic partial electrolytic bath that did not contain the metal ions. Both the deposition rate and potential in the initial region were obtained in order of the catalytic activity, depending on the alloy compositions of the substrates. The deposition rate linearly varied against the deposition time. The initial deposition potential may have also determined the structural and magnetic properties of the deposit based on the thickness of ${\mu}m$ order. Furthermore, a basic study of the electroless deposition processes on an amorphous ribbon substrate has been carried out in connection with the structural and magnetic properties of the deposits.

      • SCOPUSKCI등재

        L1<sub>2</sub>형 금속간화합물 Ni<sub>3</sub>Al중에 탄화물입자의 석출거동에 관한 연구

        한창석,구경완,오동철,Han, Chang-Suk,Koo, Kyung-Wan,Oh, Dong-Cheol 한국재료학회 2006 한국재료학회지 Vol.16 No.4

        Structural studies have been performed on precipitation hardening discovered in $L1_2-ordered\;Ni_3(Al,Cr)$ containing 0.2 to 3.0 mol% of carbon using transmission electron microscopy (TEM). Fine octahedral precipitates of $M_{23}C_6$ appeared in the matrix by aging at temperatures around 973 K after solution treatment at 1423 K. TEM examination revealed that the $M_{23}C_6$ phase and the matrix lattices have a cube-cube orientation relationship and keep partial atomic matching at the {111} interface. After prolonged aging or by aging at higher temperatures, the $M_{23}C_6$ precipitates then adopt a rod-like morphology elongated parallel to the <100> directions. Deformation at temperature below 973 K, typical Orowan loops were observed surrounding the $M_{23}C_6$ particles. At higher deformation temperatures, the Orowan loops disappeared and the morphology of dislocations at the particle-matrix interfaces suggested the existence of attractive interaction between dislocations and particles. The change of the interaction modes between dislocation and particles with increasing deformation temperature can be considered as a result of strain relaxation at the interface between matrix and particles.

      • KCI등재

        Fe 입자를 미세 분산 시킨 AlN 박막의 물리적 성질

        한창석,김장우,Han, Chang-Suk,Kim, Jang-Woo 한국재료학회 2011 한국재료학회지 Vol.21 No.1

        This paper describes the fabrication of AlN thin films containing iron and iron nitride particles, and the magnetic and electrical properties of such films. Fe-N-Al alloy films were deposited in Ar and $N_2$ mixtures at ambient temperature using Fe/Al composite targets in a two-facing-target DC sputtering system. X-ray diffraction results showed that the Fe-N-Al films were amorphous, and after annealing for 5 h both AlN and bcc-Fe/bct-$FeN_x$ phases appeared. Structure changes in the $FeN_x$ phases were explained in terms of occupied nitrogen atoms. Electron diffraction and transmission electron microscopy observations revealed that iron and iron nitride particles were randomly dispersed in annealed AlN films. The grain size of magnetic particles ranged from 5 to 20 nm in diameter depending on annealing conditions. The saturation magnetization as a function of the annealing time for the $Fe_{55}N_{20}Al_{25}$ films when annealed at 573, 773 and 873 K. At these temperatures, the amount of iron/iron nitride particles increased with increasing annealing time. An increase in the saturation magnetization is explained qualitatively in terms of the amount of such magnetic particles in the film. The resistivity increased monotonously with decreasing Fe content, being consistent with randomly dispersed iron/iron nitride particles in the AlN film. The coercive force was evaluated to be larger than $6.4{\times}10^3Am^{-1}$ (80 Oe). This large value is ascribed to a residual stress restrained in the ferromagnetic particles, which is considered to be related to the present preparation process.

      • KCI등재

        A Study on the Fabrication and Structural Properties of Al-Co/AlN-Co Thin Films

        한창석,한승오 대한금속·재료학회 2011 대한금속·재료학회지 Vol.49 No.3

        We have synthesized Al-Co/AlN-Co multilayer films with different layer thicknesses by using a Two-Facing Target Type dc Sputtering (TFTS) system. The deposited films were annealed isothermally at different temperatures and their microstructure, magnetic properties and resistivity were investigated. The magnetization of the as-deposited films was found to be very small, irrespective of layer thickness. It was found that the annealing conditions and layer thickness ratio of Al-Co to AlN-Co (LTR) were able to control the microstructure, as well as the physical properties of the prepared films. The resistivity and magnetization increased and the coercivity decreased with a decreasing LTR. A high resistivity of 2500 μΩ-cm, a magnetization of 360 emu/cm^3, and a coercivity of 5 Oe were obtained for the films with LTR=0.175.

      • SCOPUSKCI등재

        TiAl에 석출한 질화물의 결정구조와 형태

        한창석,구경완,Han, Chang-Suk,Koo, Kyung-Wan 한국재료학회 2008 한국재료학회지 Vol.18 No.1

        The crystal structures and morphologies of precipitates in $L1_0$-ordered TiAl intermetallics containing nitrogen were investigated by transmission electron microscopy (TEM). Under aging at an approximate temperature of 1073 K after quenching from 1423 K, TiAl hardens appreciably due to the nitride precipitation. TEM observations revealed that needle-like precipitates, which lie only in one direction parallel to the [001] axis of the $L1_0$-TiAl matrix, appear in the matrix preferentially at the dislocations. Selected area electron diffraction (SAED) pattern analyses showed that the needle-shaped precipitate is perovskite-type $Ti_3AlN$ (P-phase). The orientation relationship between the P-phase and the $L1_0$-TiAl matrix was found to be $(001)_P//(001)_{TiAl}\;and\;[010]_P//[010]_{TiAl}$. By aging at higher temperatures or for longer periods at 1073 K, plate-like precipitates of $Ti_2AlN$ (H-phase) with a hexagonal structure formed on the {111} planes of the $L1_0$-TiAl matrix. The orientation relationship between the $Ti_2AlN$ and the $L1_0$-TiAl matrix is $(0001)_H//(111)_{TiAl}\;and\;_H//_{TiAl}$.

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