• Journal of Welding and Joining
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• v.10 no.3
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• pp.63-72
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• 1992

The joining methods of ceramics to metals which can be expected to obtain high temperature strength are mainly classified into the solid-state diffusion bonding method and the active brazing method. Between these two, the solid-state diffusion bonding method is given attentions as substituting method for active brazing method due to being capable of obtaining higher bonding strength at high temperature and accurate bonding. In this paper, the solid-state diffusion bonding of $Al_{2}$O$_{3}$ ceramics to Ni-Cr-Mo alloy steel (SNCM21) using insert metal was carried out. The insert metal employed in this study was experimentally home-made, Ag-Cu-Ti alloy. Influence of several bonding parameters of $Al_{2}$O$_{3}$SNCM21 joint was quantitatively evaluated by bonding strength test, and microstructural analyses at the interlayer were performed by SEM/EDX. From above experiments, the optimum bonding condition of the solid-state diffusion bonding of $Al_{2}$O$_{3}$/SNCM21 using Ag-Cu-Ti insert metal was determined. Futhermore, high temperature strength and thermal-shock properties of $Al_{2}$O$_{3}$/SNCM21 joint were also examined. The results obtained are as follows. 1. The maximum bonding strength was obtained at the temperature of 95% melting point of insert metal. 2. The high temperature strength of $Al_{2}$O$_{3}$/SNCM21 joint appeared to bemaximum value at test temperature 500.deg.C and the bonding strength with increasingtemperature showed parabolic curve. 3. The strength of thermal-shocked specimens was far deteriorated than those of as-bonded specimens. Especially, water-quenched specimen after heated up to 600.deg. C was directly fractured in quenching.

• Journal of Advanced Technology Convergence
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• v.2 no.2
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• pp.9-14
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• 2023

This study is shown the result of the first year to develop an export 1050MPa-class lightweight ductile iron castings Austempered control arm through the research process to obtain the following results. First, the structure of the optimal design Layout design and development of the component, and then achieve them through the Control Arm rigidity and optimal structure design and robust design of the focus areas of the expected stress Control Arm. Second, to develop a Control Arm reflects the high rigidity and high performance lightweight structures. Control Arm them developed to meet the design and rigidity as required by the consumer through the hollow, and to develop a process for the Core. Third, through optimum alloy composition and heat treatment methods will be derived to derive the amount of iron alloy (Cu, Ni, Mo) and Austempered heat treated and tempered condition. Fourth, through the development of optimum molding technology development component to develop the optimum ADI for the low-stiffness, high-rigidity component development, it attempts to develop a high-strength casting forming technology..

• Korean Journal of Materials Research
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• v.14 no.3
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• pp.181-185
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• 2004

The mechanical properties of a bulk amorphous alloy ($Zr_{41.2}$ $Ti_{13.8}$ /$Cu_{10}$ $Ni_{10}$ $Be_{22.5}$ /at.%) before and after an annealing treatment were investigated. For the bulk amorphous alloy, the compressive strength was about 2.0 GPa, irrespective of the strain rates in the range of $10^{-4}$ to $10^3$$ sec^{-1}$ . Fine-sized nanocrystalline particles (10～100 nm) were precipitated homogeneously in the bulk amorphous matrix after the annealing treatments. Compared to the bulk amorphous materials, these composite materials, composed of the nanocrystalline phases and a bulk amorphous matrix had much different mechanical properties. The strength and strain of coposite materials measured by a compressive test showed a peak-maximum values at 7 vol.% of the nanocrystalline phases. The values in higher volume fraction of the crystalline phases in the amorphous matrix were decreased, as measured by both quasi-static and high strain rate. The decrease in fracture strength is due to presence of the dispersed large-crystalline phases in the amorphous matrix.

• Transactions of the Korean hydrogen and new energy society
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• v.1 no.1
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• pp.31-39
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• 1989

Although it has been well known that many metal hydrides are promising to use for hydrogen storage and other applications, some difficulties still remain. Metal hydrides, particularly in powder form, have very poor thermal conductivity. The hydrogen storage alloys degrade intrinsically or extrinsically during repeated hydriding and dehydriding. Elimination of these problems is very important in the practical applications. In order to prevent degradation and to improve the thermal conductivity, the hydrogen storage characteristics of rare-earth type alloy encapsulated with Cu or Ni by means of chemical plating have been investigated. No changes has occured in hydrogen absorption capacity and equilibrium pressure even though the alloy powder is microencapsulated. The first hydrogen absorption rate of the alloy encapsulated increased considerably comparing to uncapsulated sample. In the case of encapsulating the fine powder ($>10{\mu}m$) and subsequent compacting by $8ton/cm^2$, shape of compact is maintained regardless of hydriding and dehydriding. The degree of degradation of the alloy caused by impurity gas of CO or $O_2$ was decreased prominently by encapsulation.

• Transactions of the Korean hydrogen and new energy society
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• v.9 no.4
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• pp.169-176
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• 1998

An experimental study on effect of vapor-cooled heat stations in a 5.5 liter cryogenic vessel has been performed. The cryogenic vessel is made of stainless steel of thickness of 1mm and insulated by the combined insulation of vacuum, MLI(multi-layer insulation) and vapor-cooled radiation shield. Vapor-cooled heat stations are also constructed based on the 1-dimensional thermal analysis to reduce the heat inleak through a filling tube. Thermal analysis indicates that the vapor-cooled heat stations can substantially enhance the performance of vessel for cryogenic fluids with high $C_p/h_{fg}$ where $C_p$ the specific heat and $h_{fg}$ the heat of vaporization, such as $LH_2$ and LHe. The experimental results for $LN_2$ shows that the total heat inleak into inner vessel consists of 14% radiation and 86% conduction through the filling tube. Therefore, it is expected that the conduction heat in leak of the vessel for high $C_p/h_{fg}$ cryogenic fluids can be significantly reduced. powders. The amount of copper coating was 20wt%. In order to examine corrosion behavior of the electrodes, the corrosion current and the current density, in 6M KOH aqueous solution after removal of oxygen in the solution, were measured by potentiodynamic and cyclic voltamo methods. The results showed that Co in the alloy increased corrosion resistance of the electrode whereas Ni decreased the stability of the electrode during the charge-discharge cycles. The electrode used Si sealant as a binder showed a lower corrosion current density than the electrode used PTFE and the electrode used Cu-coated alloy powders showed the best corrosion resistance.

• Journal of Korea Foundry Society
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• v.14 no.5
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• pp.429-437
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• 1994

Influence of interfacial structure between matrix and particle in A356/coated SiC composite fabricated by squeeze casting method was studied. Experimental variables are types of coated metallic film on SiC particles such as Cu, Ni-P, and applied pressure for squeeze casting. It was found that coating treatment on SiC particles improves the wetting of liquid A356 alloy on SiC particles. SiC particle distribution is very homogeneous in A356 matrix alloy which is fabricated by squeeze casting. Analysing the surface morphology of fractured A356/coated SiC, it was concluded that metallic thin film by coating treatment on SiC particle improves the interfacial bonding between particle and matrix, and so does on mechanical properties such as tensile strength. However, there was on significant difference in hardness between those composite made of as-received SiC particle and coated SiC particle.

• Transactions of Materials Processing
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• v.10 no.5
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• pp.425-432
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• 2001

In order to investigate the influences of process parameters on the shape of lead frame, experimental study has been carried out. In the experiment, dimensional accuracy of the die sets, measurement accuracy has been managed carefully enough to simulate actual lead frame blanking process. With the blanking of square-shaped specimen, the effects of clearance, strip holding pressure and bridge width on the shape of blanked profile have been investigated. Experimental results show that the burnish ratio is increased as the clearance decreases. the strip holding pressure increases, and bridge width increases. Although the results seems to be similar to the ordinary blanking, the lead frame blanking shows a subtle different characteristics to the ordinary blanking due to the narrow bridge width.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.64-67
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• 2009

Vibrational micro-forming of pyramidal shape patterns was conducted for an Al superplastic alloy, Al 5083 and a Zr-based bulk metallic glass, $Zr_{62}Cu_{17}Ni_{13}Al_8$. A vibrational micro-forming system was specially designed for generating vibrational load by combining a PZT actuator with a signal generator. Single crystal Si micro dies with wet-etched pyramidal patterns were used as master dies for vibrational micro-forming. The micro-formed pattern height was increasing with increasing the frequency of the vibrational load. In particular, the vibrationally-microformed pattern height was similar or even higher than the statically-microformed pattern height when the load frequency exceeded about 125 kHz. It was also observed that the crystal grains affect the surface quality of the microformed pattern and the distribution of the pattern height in the die cavity array.

• Korean Journal of Materials Research
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• v.11 no.3
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• pp.171-177
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• 2001

The thermal and mechanical properties of amorphous Z $r_{62-x}$N $i_{10}$C $u_{20}$A $l_{8}$ $Ti_{x}$ (x=3, 6, 9at%) alloys were investigated. The crystallization process was confirmed as amorphous longrightarrow amorphous + Z $r_2$A $l_3$+ Zr + (Ni,Ti) longrightarrow Z $r_2$Cu + Al + (Ni,Ti) for 3at%Ti, amorphous longrightarrow amorphous + Al longrightarrow $Al_2$Ti + NiZr + CuTi for 6at%Ti and amorphous longrightarrow amorphous + Zr + Al longrightarrow Zr + $Al_2$Zr + Al $Ti_3$+ CuTi for 9at%Ti. lickers hardness ( $H_{v}$ ) increased with increasing volume fraction( $V_{f}$ ) of pricipitates for all concerned compositions. Tensile fracture strength ($\sigma_{f}$ ) showed a maximum value 1219MPa at $V_{f}$ = 38% for 3at%Ti, 1203MPa at $V_{f}$ = 2% for 6at%Ti and 1350MPa at $V_{f}$ = 5% for 9at%Ti. The $\sigma_{f}$ was rapidly decreased after showing the maximum value. The $V_{f}$ corresponding to rapidly decreased $\sigma_{f}$ coincided with the $V_{f}$ transited from ductile to brittle fracture surface.ace.

• Resources Recycling
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• v.11 no.1
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• pp.9-18
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• 2002

Printed wiring boards(PWBs) of the obsolete computers are composed of various organic and inorganic compounds as well as metals and alloys. As convinced that the valuable metals obtained from the PWBs are effectively utilized as secondary resources when recovered by economical methods, in this study, an investigation for characterizing the physical separation techniques is conducted. For the recovery of them, the sockets and chips dismantled from PWBs by scraping and residual resin boards are subjected to the appropriate separation processes according to the physical properties of each part. In the case of crushed socket scraps size ranged from -2.36 mm to +1.18 mm, approximately 97 wt% of the product obtained by magnetic separation consists of metallic compounds. In the case of chip scraps, 97% of Fe-Ni alloy and 95% of Cu metal are recovered by the combined process of air classification and dry magnetic separation in the size range from -2.36 mm to +0.15 mm. Ball milling is adopted in order to improve the removal efficiency of the thin-printed metallic materials on the residual resin boards and approximately 77% of Cu metal is recovered by zigzag separation after ball milling.