• Journal of Korea Foundry Society
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• v.28 no.6
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• pp.243-251
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• 2008

자동차 및 항공기 부품용 고온 다이캐스팅 마그네슘 합금에 대한 연구가 활발히 진행되고 있다. 알루미늄을 주된 합금원소로 하여 희토류원소나 알칼리토금속 등을 첨가하는 3원계 합금 및 각 원소들을 조합하는 4원계 합금이 개발되었다. 이들 합금의 크립 저항성은 금속간 상에 의한 결정 입계 강화에 기인한다. 그 동안의 합금조성 개발의 핵심은 결정 입계의 이동을 유발하여 고온 변형을 유발하는 고온 불안정 석출상의 생성을 억제하는 것이었다. Mg-Al계 합금에 희토류원소를 첨가하면 고온 안정상의 생성으로 고온 특성이 향상되지만 희토류원소의 경제성이 단점이다. 고비용의 희토류원소를 대신하기 위해 알칼리토금속을 첨가하는 합금 및 이들 원소를 조합하는 합금이 개발되었다. 본고에서는 알칼리토금속을 첨가할 경우에 발생하는 생산성의 저하 등의 단점을 보완하는 알칼리토금속산화물이 첨가된 합금을 소개하였는데 이는 1) 비고용성 2) 융점유지 3) 주조성유지 4) 재활용성 5) 경제성 등의 특징이 있다.

• Transactions on Electrical and Electronic Materials
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• v.1 no.2
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• pp.32-37
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• 2000

Effect of alloying element additions to Ag on thermal conductivity and electrical conductivity of sheath materials for Bi-Pb-Sr-Ca-Cu-O(BSCCO) tapes has been characterized. The thermal conductivity at low temperature range (10~300K) of Ag and Ag alloys were evaluated by both direct and indirect measurement techniqueas and compared with each other, It was observed that the thermal conductivity decreases with increasing the content of alloying element such as Au, Pd and Mg. Thermal conductivity of pure Ag at 3 0K was measured to be 994.0 W(m.K) on the other hand, the corresponding values of $Ag_{0.9995}Mg_{0.0005}$, $Ag_{0.974}$, $Au_{0.025}$, $Mg_{0.001}$, $Ab_{0.973}$, $Au_{0.025}$, $Mg_{0.002}$ and $Ag_{0.92}$, $Pb_{0.06}$, $Mg_{0.02}$ were 342.6, 62.1, 59.2 and 28.9 W(m.K), respectively, indicating 3 to 30 times lower than that of pure Ag. In addition, the thermal conductivity of pure Ag measured by direct and indirect measurement techniques was 303.2 and 363.8 W(m.K) The difference in this study is considered to be within an acceptable error range compared to the reference data.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.153-153
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• 2017

The application of the coating supports the mechanical characteristics of the implant, and various materials and coatings are currently being used in the implant in a way to accelerate adhesion. Especially, plasma electrolytic oxidation (PEO) coating has been proposed continually with good surface treatment of titanium alloys. Also, the PEO process can incorporate Ca and P ions on the titanium surface through variables varied factor. PEO process for bioactive surface has carried out in electrolytes containing Ca and P ions. Natural bone is composed of mineral elements such as Mg, Si, Zn, Sr, and Mn, etc. Especially, Mg and Si of these elements play role in bone formation and growth after clinical implantation of bio-implants. In this study, corrosion charateristics of PEO-treated Ti-6Al-4V alloy in solution containing Si and Mg ions has been investigated using several experimental techniques. The PEO-treated surfaces were identified by X-ray diffraction, using a diffractometer (XRD, Philips X' pert PRO, Netherlands) with Cu $K{\alpha}$ radiation. The morphology was observed by field-emission scanning electron microscopy (FE-SEM, Hitachi 4800, Japan) and energy-dispersive X-ray spectroscopy (EDX, Oxford ISIS 310, England). The potentiodynamic polarization and AC impedance tests for electrochemical degradations were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to + 2000mV.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.191-198
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• 2022

Zirconia and titanium alloys, which are mainly used for dental implant materials, have poor osseointegration and osteogenesis abilities due to their bioinertness with low bioactivity on surface. In order to improve their surface bioinertness, surface modification with a bioactive material is an easy and simple method. In this study, akermanite (Ca₂MgSi₂O₇), a silicate-based bioceramic material with excellent bone bonding ability, was synthesized by a solid-state reaction and investigated its bioactivity from the analysis of surface dissolution and precipitation of hydroxyapatite particles in SBF solution. Calcium carbonate (CaCO₃), magnesium carbonate (MgCO₃), and silicon dioxide (SiO₂) were used as starting materials. After homogeneous mixing of starting materials by ball milling and the drying of at oven, uniaxial pressing was performed to form a compacted disk, and then heat-treated at high temperature to induce the solid-state reaction to akermanite. Bioactivity of synthesized akermanite disk was evaluated with the reaction temperature from the immersion test in SBF solution. The higher the reaction temperature, the more pronounced the akermanite phase and the less the surface dissolution at particle surface. It resulted that synthesized akermanite particles had high bioactivity on particle surface, but it depended on reacted temperature and phase composition. Moderate dissolution occurred at particle surfaces and observed the new precipitated hydroxyapatite particles in synthetic akermanite with solid-state reaction at 1100℃.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.157-168
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• 2006

Recently, interest in using Al alloys in ship construction instead of fiber-reinforced plastic (FRP) has increased because of the advantages of A) alloy ships over FRP ships, including high speed, increased load capacity. and ease of recycling. This paper investigated the mechanical and electrochemical properties of Al alloys in a slow strain rate test under various potential conditions. These results will provide reference data for ship design by determining the optimum protection potential regarding hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys do not corrode on formation of a film that has resistance to corrosion in neutral solutions. In seawater, however, $Cl^-$ ions lead to the formation and destruction of a Passive film. In a potentiostatic experiment. the current density after 1200 sec in the Potential range of $-0.68\~-1.5\;V$ was low. This low current density indicates the protection potential range. Elongation at an applied potential of 0 V was high in this SSRT. However, corrosion protection under these conditions is impossible because the mechanical properties are worse owing to decreased strength resulting from the active dissolution reaction in parallel parts of the specimen. A film composed of $CaCO_3\;and\;Mg(OH)_2$ confers corrosion resistance. However, at potentials below -1.6 V forms non-uniform electrodeposition coating, since there is too little time to form a coating. Therefore, we concluded that the mechanical properties are poor because the effect of hydrogen gas generation exceeds that of electrodeposition. Comparison of the maximum tensile strength, elongation, and time to fracture indicated that the optimum protection potential range was from -1.45 to -0.9 V (SSCE).

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.04a
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• pp.54-58
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• 1993

Cu, Si, Mg, Ca, Cd, Sn, Pb등이 첨가되는 Al계 bearing 합금은 베어링 특성이 우수하여 최근 자동차드의 엔진 부품용 베어링소재로 많이 사용되어지고 있다. 합금원소 Si는 합금의 경도를 향상시키며 Si-rich한 경한 입자를 생성시켜 소착저항력(antiseizure)을 향상시키며 또한 합금의 주조성도 향상시켜 내마모성이 요구되는 Al계 베어링 합금에 주합금원소로 첨가된다. 본 연구에서는 강제죠반법과 급냉응고법을 이용하여 Al-Pb-Gu계와 Al-Si-Gu-Pb계 베어링합금을 제조하였다. 베어링합금이 급냉응고법으로 제조되었기 때문에 합금의 기지에는 Cu가 과포된 상태로 존재하여 석출경화에 앞서 행하여지는 용체화처리와 같은 효과가 얻어졌다. 본 실험에서는 Cu가 과포화된 기지를 갖는 주조상태의 시료를 시효열처리하여 석출경화된 베어링합금을 얻어서 석출경화에 의한 기지강화가 베어링합금의 내마모성질에 어떠한 효과를 가져오는지 규명하였다.

• Korean Journal of Materials Research
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• v.17 no.12
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• pp.637-641
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• 2007

The total energy and strength of Mg alloy doped with Al, Ca and Zn, were calculated using the density functional theory. The calculations was performed by two programs; the discrete variational $X{\alpha}\;(DV-X{\alpha})$ method, which is a sort of molecular orbital full potential method; Vienna Ab-initio Simulation Package (VASP), which is a sort of pseudo potential method. The fundamental mixed orbital structure in each energy level near the Fermi level was investigated with simple model using $DV-X{\alpha}$. The optimized crystal structures calculated by VASP were compared to the measured structure. The density of state and the energy levels of dopant elements was discussed in association with properties. When the lattice parameter obtained from this study was compared, it was slightly different from the theoretical value but it was similar to Mk, and we obtained the reliability of data. A parameter Mk obtained by the $DV-X{\alpha}$ method was proportional to electronegativity and inversely proportional to ionic radii. We can predict the mechanical properties because $\Delta{\overline{Mk}}$is proportional to hardness.

• Journal of Korea Foundry Society
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• v.20 no.1
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• pp.38-45
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• 2000

The remelting for recycling or thin aluminum scrap, such as aluminum chip generally involves melting of these pieces submerged in molten salt flux. In this study, the effects of salt flux compositions and alloying elements on the aluminum dropletscoalescence and oxide film removal were studied in 99.8%Al, Al-1.01%Cu, Al-1.03%Si, and Al-1.38%Mg alloys as a function of holding time at $740^{\circ}C$ Salt fluxes based on NaCl-KCl(1:1) with addition of 5wt.% fluorides(NaF, $Na_3AlF_6$, $CaF_2$) or 5 wt.% chloride($MgCl_2$, $AlCl_3$) were used. The experimental results show that NaCl-KCl(1:1) with addition of 5 wt.% fluorides exhibits better coalescence ability than that with chlorides. The oxide film is not removed by NaCl-KCl(1:1) with addition of 5 wt.%chlorides, while it is removed by NaCl-KCl(1:1) with addition of 5 wt.% fluorides. The aluminum droplets coalescence and oxide film removal by salt fluxes are related to interfacial tension tension between metal and salt flux.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.75-75
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• 2018

Commercially pure titanium (CP-Ti) and Ti-6Al-4V alloys have been widely used in implant materials such as dental and orthopedic implants due to their corrosion resistance, biocompatibility, and good mechanical properties. However, surface modification of titanium and titanium alloys is necessary to improve osseointegration between implant surface and bone. Especially, when titanium oxide nanotubes are formed on the surface of titanium alloy, cell adhesion is greatly improved. In addition, plasma electrolytic oxide (PEO) coatings have a good safety for osseointegration and can easily and quickly form coatings of uniform thickness with various pore sizes. Recently, the effects of bone element such as magnesium, zinc, strontium, silicon, and manganese for bone regeneration are researching in dental implant field. The purpose of this study was researched on the surface morphology of PEO-treated Ti-6Al-4V alloy after anodic titanium oxide treatmentusing various instruments. Ti-6Al-4V ELI disks were used as specimens for nanotube formation and PEO-treatment. The solution for the nanotube formation experiment was 1 M $H_3PO_4$ + 0.8 wt. % NaF electrolyte was used. The applied potential was 30V for 1 hours. The PEO treatment was performed after removing the nanotubes by ultrasonics for 10 minutes. The PEO treatment after removal of the nanotubes was carried out in the $Ca(CH_3)_2{\cdot}H_2O+(CH_3COO)_2Mg{\cdot}4H_2O+Mn(CH_3COO)_2{\cdot}4H_2O+Zn(CH_3CO_2)_2Zn{\cdot}2H_2O+Sr(CH_2COO)_2{\cdot}0.5H_2O+C_3H_7CaO_6P$ and $Na_2SiO_3{\cdot}9H_2O$ electrolytes. And the PEO-treatment time and potential were 3 minutes at 280V. The morphology changes of the coatings on Ti-6Al-4V alloy surface were observed using FE-SEM, EDS, XRD, AFM, and scratch tester. The morphology of PEO-treated surface in 5 ion coating solution after nanotube removal showed formation or nano-sized mesh and micro-sized pores.

• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.161-165
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• 2005

Recently, it is on the increase interest for Al alloy with new material for ship application to substitute for FRP ship. The reason is thatAl alloy ship has beneficial characteristics such as high sea speed, increase of loadage and easy to recycle compared with FRP ship. In this paper, mechanical and electrochemical properties are investigated by slow strain rate test experiment in various applied potential condition. These results will provide as reference data to design ship by deciding optimum protection potential regard to hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys are not corroded with forming film which has the corrosion resistance property in neutral solution. However, it was observed that formation and destruction of passive film by $Cl^-$ ion in sea water environment. At comparison of current density after 1200 sec in potentiostatic experiment, the current density in the potential range of -0.68 $\~$-1.5 V is shown low value. The low current density means protection potential range. Elongation in applied potential of 0 V was high. However, the corrosion protection application in this condition is impossible potential because the toughness is low value by decreasing strength by active dissolution reaction at parallel part of specimen. The film composed with $CaCO_3$ and $Mg(OH)_2$ has a corrosion resistance property. However, the uniform electrodeposition coating at below -1.6 V potential is not formed since the time to form the uniform electrodeposition coating is short. Therefore, it is concluded that mechanical property is poor because effect by hydrogen gas generation is larger than that of electrodeposition coating. It is concluded that the optimum protection potential range from comparison of_maxim urn tensile strength, elongation and time to fracture is -1.3$\~$0.7 V (SSCE).