• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.380-385
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• 2004

The efficiency of complex slurry preparation route for developing the high performance SiC matrix of RS-SiCf/SiC composites has been investigated. The green bodies for RS-SiC materials prior to the infiltration of nw/ten silicon were prepared with various C/SiC complex matrix slurries, which associated with both different sizes of starting SiC particles and blending ratios of starting SiC and carbon particles. The characterization of RS-SiC materials was examined by means of SEM, TEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, process optimization methodology is also discussed. The flexural strength of RS-SiC materials greatly depended on the content of residual Si. The decrease of starting SiC particle size in the C/SiC complex slurry was effective for improving the flexural strength of RS-SiC materials.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.528-534
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• 2004

Using the nano Fe powders having 50 nm in diameter, Fe compact bodies were fabricated by injec-tion molding process. The relationship between microstructure and material properties depending on the volume ratio of powder/binder and sintering temperature were characterized by SEM, TEM techniques. In the compact body with the volume percentage ratio of 45(Fe powder) : 55(binder), which was sintered at $700^{\circ}C,$ the relative density was about $97{\%},$ and the values of volume shrinkage and hardness were about $66.3{\%}$ and 242.0 Hv, respec-tively. Using the composition of 50(Fe powder) : 50(binder) and sintered at $700^{\circ}C,$ the values of relative density, volume shrinkage and hardness of Fe sintered bodies were $73.3{\%},\;47.6{\%}$ and 152.8 Hv, respectively. They showed brittle fracture mode due to the porous and fine microstructure.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.1
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• pp.2-9
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• 2003

The aluminum alloy which is light and has excellent thermal conductivity and iron base alloy that is remarkable heat-resistece and wear resistence properties were bonded together. The bond was created between a stationary and a rotating member by using the frictional heat generated between them while subjected to high normal forces on the interface of Al alloy and iron base alloy. The microstructure of the bonded interface of friction welding and the strength in the bonded interface formed under various bonding conditions were examined through TEM, SEM with EDX and triple bending test. In interface of bonding materials formed after various heat treatment, bonding strength was substantially different, resulting from formation of intermetallic compound or softening during annealing.

• Journal of Korea Foundry Society
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• v.10 no.5
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• pp.417-425
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• 1990

The purpose of this study is to investigate the effect of Be addition on the microstructure and mechanical properties of as-cast and homogenization treated Al-Li-(Be)alloys. The ductility of as-cast Al-Li alloy was increased by the addition of Be and the fracture morphology was changed from brittle to ductile mode. Also, hardness and strength have been decreased by homogenization treatment. The morphology of eutectic structure which consists of ${\alpha}(Al)$ and ${\alpha}(Be)$ was changed from lammellae to spherical type by homogenization treatment. The shape of ${\alpha}(Be)$ phase has been revealed as hollow type by TEM observation. It consists of outer surfaces with well defined crystal facets and the core filled with ${\alpha}(Al)$. The microstructure of as-cast Al-Li-Be alloys showed coarse ${\delta}'$, fine ${\delta}'$, and coarse ${\delta}$ phases. The coarse and fine ${\delta}'$ phases were formed at Be-rich phase /matrix interfaces and in matrix, respectively. By homogenization treatment, the ${\delta}$ phase in Al-Li and Al-Li-Be alloys dissolved and the size of ${\delta}$ phase in Al-Li-Be alloys was finer than that of Al-Li alloy.

• Journal of the Korean Ceramic Society
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• v.46 no.2
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• pp.181-188
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• 2009

The electrical property and microstructure in $BaTiO_3$ ceramics doped rare-earth ions with intermediate ionic size ($Dy^{3+},Ho^{3+},Y^{3+}$) were investigated. Microstructures have been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Incorporation of rare-earth ions to $BaTiO_3$ ceramics depended on their ionic radius sensitively. Compared to Ho and Y ions, Dy ions provide $BaTiO_3$ ceramics with the high rate of densification and well-developed shell formation, due to their high solubility in the $BaTiO_3$ lattice, but the microstructure of Dy doped $BaTiO_3$ ceramics is unstable at high temperature, because Dy ions could not play a role of grain growth inhibition, leading to diffuse into $BaTiO_3$ lattice continuously after completion of densification during sintering. Comparing electrical property and microstructure, it is shown that the reliability of capacitor improved by high shell ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.111-114
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• 2000

Growth characteristics and microstructure of AlN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the microstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.2
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• pp.101-112
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• 1995

A study was made to examine the effects of heat-treatment on the microstructures of Cu-bearing HSLA steels. The details of microstructures were studied by using optical microscopy(OM), transmission electron microscopy(TEM) and hardness test. The as-rolled microstructure of HSLA-A consists of ferrite (${\alpha}$) whereas that of HSLA-B consists of needle-shaped phase. The difference in microstructure can be ascribed to the different amount of Ni, Mn, Mo, Cu which affect the hardenability. The austenite grain size is very small up to $1000^{\circ}C$ owing to the Nb-precipitates. As the austenitizing temperature increases above $1000^{\circ}C$, the austenite grain grows rapidly. There are two hardness peaks in the hardness versus temperature curve, at $500^{\circ}C$ and at $675^{\circ}C$ (HSLA-A), $725^{\circ}C$ (HSLA-B). The peak at $500^{\circ}C$ result from the formation of Cu-precipitates and second hardness peak is created due to the formation of M-A constituents. The hardriess decrease in HSLA-B steel with ageing temperature is small because of the higher amounts of Cu than HSLA-A steel. The fine, round ${\varepsilon}$-Cu precipitates grow with ageing temperature and finally transform into rod shape.

• Journal of the Korean institute of surface engineering
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• v.27 no.5
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• pp.261-272
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• 1994

Both Cu-Cr and Cu-Ti alloy films with different composition were prepared by dc magnetron sputtering onto polyimide substrate and their adhesion and microstructure were observed. In addition, the effect of heat treatment at $400^{\circ}C$ for 2 hours on the variation of adhesion properties and on the changess of microstructure were investigated. Cu-Cr alloy films have crystalline structure of either for or bcc phase depending on the composition of the film. However, the Cu-Ti alloy film forms fcc phase at low Ti concentration while it forms an amorphous phase as the Ti concentration in the films is increased to more than 25at.%. TEM analysis reveal that the microstructure of Cu-Cr and Cu-Ti films forms an open structure with vacant spaces. The adhesion between Cu-Cr, Cu-Ti alloy films and polyimide substrate is relatively good before the heat treatment, but is noticeably reduced after the heat treatment. In particular, the adhesion strength is significantly reduced in the Cu-Ti alloy films after the heat treatment. The reduction of adhesion strength after the heat treatment is identified to relate with the formation of oxide phases at the metal/polyimide interface by AES(Auger Electron Spectroscopy).

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.793-800
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• 2012

The effect of cold rolling on the microstructural evolution in 22Cr-0.2N micro-duplex stainless steel was investigated. The 22Cr-xNi-yMn-0.2N duplex stainless steel plates with various Ni and Mn contents were fabricated. The steels were vacuum induction melted and hot rolled, followed by annealing treatment at the temperature range of $1000-1100^{\circ}C$, in which both the austenite and ferrite phases were stable. The volume fraction of the ferrite phase depending on the alloy compositions of Ni and Mn increased with an increase in the annealing temperature. Grain growth in the ferrite phase occurred markedly after cold rolling followed by annealing, while fine recrystallised grains were still found in the austenite phase. A large number of martensite laths was found in the microstructure of cold rolled steels, which should be formed by strain-induced martensite from the austenite phase. The intersections of stacking faults were revealed by TEM observation. The volume fraction of the martensite phase increased with an increase of the reduction ratio by cold rolling.

• Korean Journal of Metals and Materials
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• v.49 no.6
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• pp.440-447
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• 2011

To improving the mechanical properties of Mg alloys at high temperature, we investigated the mechanical properties at high temperature and the change of microstructure of Mg-6 wt%Zn-0.4 wt%Mn and Mg-6 wt%Zn-0.4 wt%Mn-1 wt%Ag alloys on age treatment that have a stable MgZn phase at high temperature and $AgMg_4$ improving yield stress. In order to predict thermodynamic data of Mg alloys, a phase diagram and precipitation phase were calculated using a thermodynamic program, and it was confirmed that the MgZn and $AgMg_4$ phase existed as main precipitation in this alloys. The experimental data examined using DSC and XRD were comparable with the calculated data for reliability. In order to analysis the microstructure and precipitate phase during aging treatment, it was measured by SEM/EDS and TEM. Lastly, mechanical properties of the MgZn and $AgMg_4$ phase were measured by a tensile test at high temperature.