• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1048-1049
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• 2006

Rapidly solidified ribbon-consolidation processing was applied for preparation of high strength bulk Mg-Zn-Gd alloys. Mg alloys have been used in automotive and aerospace industries. Rapid solidification (RS) process is suitable for the development of high strength Mg alloys, because the process realizes grain-refinement, increase in homogeneity, and so on. Recently, several nanocrystalline Mg-Zn-Y alloys with high specific tensile strength and large elongation have been developed by rapidly solidified powder metallurgy (RS P/M) process. Mg-Zn-Y RS P/M alloys are characterized by long period ordered (LPO) structure and sub-micron fine grains. The both additions of rare earth elements and zinc remarkably improved the mechanical properties of RS Mg alloys. Mg-Zn-Gd alloy also forms LPO structure in -Mg matrix coherently, therefore, it is expected that the RS Mg-Zn-Gd alloys have excellent mechanical properties. In this study, we have developed high strength RS Mg-Zn-Gd alloys with LPO structure and nanometer-scale precipitates by RS ribbon-consolidation processing. $Mg_{97}Zn_1Gd_2$ and $Mg_{95.5}Zn_{1.5}Gd_3$ and $Mg_{94}Zn_2Gd_4$ bulk alloys exhibited high tensile yield strength (470 MPa and 525 MPa and 566 MPa) and large elongation (5.5% and 2.8% and 2.4%).

• Journal of Korea Foundry Society
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• v.15 no.2
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• pp.164-174
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• 1995

New metallic powder making processes, named "Centrifugal Emulsification Process(CEP)" and "Mixer and Settler(MS)" have been developed to synthesize rapid solidified metallic powders. Through CEP and MS processings, the high temperature metals as well as the low temperature alloys are manufactured. Also, the effects of rapid solidification on the undercooling, solidification rate and crystallization behaviors can be evaluated effectively through the processes. The standard deviations of the synthesized typical Pb-Sn eutectic powders are 1.63 and 1.51 for CEP and MS respectively, and the average size of the MS powders was $18{\mu}m$. The possibility of the customized not only size and shape control but microstructure control was also shown. Both of the new methods can be applied to continuous powder making processes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.57-67
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• 1997

The solidification process of Al 4.5%Cu alloy is numerically studied in the presence of contact resistance between mold and cast. Natural convection is considered in the liquid and mushy regions. The porosity approach is applied to the mushy zone modeling and linear variation of the solid fraction on the temperature is assumed. Results show that the mushy region is wider in the case with a contact resistance compared to the perfect contact condition. The temperature of the cast with a temporal variation in the contact heat transfer coefficient changes very rapidly in the early stage of the casting process compared to that with constant contact heat transfer coefficient.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.341-348
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• 2019

This paper reports the microstructure and electrochemical properties of Si-Al-Fe ternary amorphous alloys prepared by rapid solidification as an anode for lithium secondary batteries. The microstructure was analyzed using XRD and HR-TEM with EDS mapping. In accordance with DSC analysis, annealing was performed to crystallize the active nano-Si in the amorphous alloy. Thus, nano-Si forms (~80 nm) embedded in the matrix alloy, such as $Fe_2Al_3Si_3$, $FeSi_2$, and $Fe_{0.42}Si_{2.67}$, were successfully synthesized. The electrode based on the Si-Al-Fe ternary alloy delivered an initial discharge capacity of approximately $700mAh^{g-1}$, and exhibited a high Coulombic efficiency of 99.0~99.6% from the $2^{nd}$ to $70^{th}$ cycles.

• Journal of Advanced Marine Engineering and Technology
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• v.7 no.1
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• pp.79-90
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• 1983

The examination for the changes of structures and mechanical properties in directionally solidified Al-Fe-Ni alloys containing the small amount of Fe and Ni was carried out by the varying the composition and solidification rate R of alloy, provided that the temperature gradient was 80 .deg.C/cm. The result were obtained as follows. A) In proportion to the increase of the solidification rate (R), the crystallized phase of this alloy was changed from the Ribbon-type structure to the Rod-type structure. B) The strength was rapidly increased in the changing process of composite shape from the Ribbon-type to the Rod-type with the solidification rate (R) increasing. C) The fiber stress (${\sigma}^f$) and Young's modulus ($E_f$) calculated for the Rod-type structure were 220 kg/$mm^2$ and 11, 800 kg/$mm^2$ respectively, which were in good accord with the rule of Mixtures.

• Journal of Korea Foundry Society
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• v.30 no.1
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• pp.34-45
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• 2010

The effects of alloy elements and cooling rate on the solidification path and the formation behavior of $\beta$ phase in Fe-containing Al-Si alloys were studied based on the thermodynamic analysis and the pertinent experiments. The thermodynamic calculation was systematically performed by using Thermo-Calc program. For the thermodynamic analysis in high alloy region of Al-Si-Fe ternary system, a thermodynamic database for Thermo-Calc was correctly updated and revised by the collected up-to-date references. For the thermodynamic-based prediction of various solidification paths in Fe-containing Al-Si system, liquidus projection of Al-Si-Fe ternary system, including isotherms, invariant, monovariant, bivariant reactions and equilibrium temperatures, was calculated and analyzed as functions of composition and temperature. The calculated results were compared to the experimental results using various casting specimens. In order to analyze various solidification sequences as functions of Si and Fe content, 4 representative alloy compositions, low Fe content in both low and high Si contents and high Fe content again in both low and high Si contents, were designed in this study. For better understanding of the influence of cooling rate on the formation behavior of $\beta$ phase, 4 alloys were solidified under furnace and rapidly cooled conditions. Cooling curves of solidified alloys were recorded by thermal analysis. Various important solidification events were evaluated using the first derivative-cooling curves. Microstructures of the casting samples were studied by the combined analysis of optical microscopy (OM) and scanning electron microscopy (SEM).

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.80.2-80.2
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• 2007

• Journal of Korea Foundry Society
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• v.26 no.2
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• pp.92-97
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• 2006

Contact material is widely used as electrical parts. Ag-Cd alloy has a good wear resistance and stable contact resistance. But the disadvantages of Ag-Cd alloy are coarse Cd oxides and harmful metal, Cd. To solve the disadvantages of that, Ag-Sn alloy that has stable and fine Sn oxide at high temperature has been developed. In order to optimize Sn amount that affects the formation of the oxide layer on the surface, we worked for the microstructures and properties of Ag-Sn material fabricated by rapid solidification process. The experimental procedure were melting using high frequency induction, melt spinning, and internal oxidation. We have shown that the optimized Sn amount for high hardness is 7.09 wt%Sn. Surface oxide layer forms when Sn amount is over 9.45 wt%. The size of Sn oxide is 20 nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.86-91
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• 2007

Contact material is widely used as electrical parts. Ag-CdO has a good wear resistance and stable contact resistance. But the disadvantages of Ag-Cd alloy are coarse Cd oxides and harmful metal, Cd. Then Ag-Sn alloy that has stable and fine Sn oxide at high temperature has been developed. In order to investigate the effect of Te additional that affects the formation of the oxide layer on the surface and the formation of oxide in matrix Ag, we studied the microstructures and properties of Ag-Sn-In(-Te) material fabricated by rapid solidification process. The experimental procedure were melting using high frequency induction, melt spinning, and internal oxidation. Specimens were examined and analyzed by Transmission electron microscopy(TEM), energy dispersive X-ray spectroscopy(EDS) and Vickers hardness. As a result, internal oxidation was completed even at $600^{\circ}C$. Te forms coarse $In_{2}TeO_{6}$ phase and makes fine and well dispersed $SnO_{2}$ Phase. 0.3 wt% Te shows favorable properties.

• Korean Journal of Materials Research
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• v.9 no.4
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• pp.386-391
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• 1999

The charge-discharge, the high-rate dischargeability, and the self discharge characteristics of the electrodes composed of rapidly solidified ZrV\ulcornerMn\ulcornerMo\ulcornerNi\ulcorneralloy, which has the form of partial substitution of Mn, Mo, Ni for V in $ZrV_2$ were studied. The alloys were prepared using Arc & RSP(Rapid Solidification Process) at the rotating roller speed of 2000 and 5000 rpm. Some of them were received heat treatment at$ 560 ^{\circ}C$ for 1 hour after the solidification to investigate the effect of the heat treatment. It was fond that cycle life was significantly improved by RSP, whereas discharge capacity, activation rte and high rate dischargeability were decreased compared with the conventional arc melting method. The capacity loss seems to be due to the loss of the crystallinity and the increase of the cycle life ascribed to the presence of the amporphous phase as well as the refined grain size of less than 0.2$\mu\textrm{m}$. Heat treatment of the alloy cooled at 2000 rpm improved the cycle life. In case of the alloys cooled at 5000 rpm, both the discharge capacity and the activation rate were significantly improved by the heat treatment.