• 대한금속재료학회지
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• 제47권4호
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• pp.223-227
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• 2009

The precipitates, hardness, and tensile properties of Al-6.2Si-2.9Cu AC2B alloy were investigated with respect to solution treatment time at $500^{\circ}C$. $Al(Cu)-Al_2Cu$ eutectic, Si, ${\theta}-(Al_2Cu)$, and $Q-(Al_5Cu_2Mg_8Si_6)$ phases were observed in the as-cast specimen. With increasing the solution treatment time at $500^{\circ}C$, the $Al(Cu)-Al_2Cu$ eutectic and ${\theta}-(Al_2Cu)$ phases were gradually reduced and finally almost disappeared in 5 h. The mechanical properties, such as hardness, tensile strength, and elongation, were improved with solution treatment time until about 5 h due to the dissolution of the $Al_2Cu$ particles. With further holding time, the mechanical properties did not change much. The solution treated specimens for over 5 h at $500^{\circ}C$ exhibit almost the same tensile properties even after aging at $250^{\circ}C$ for 3.5 h. Accordingly, the optimal solution treatment condition of the Al-Si-Cu AC2B alloy is considered to be 5 h at $500^{\circ}C$.

• 한국표면공학회지
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• 제53권2호
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• pp.59-66
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• 2020

Effects of Na₂SiO₃ concentration added into 0.1 M NaOH + 0.05 M NaF solution on the formation behavior and properties of PEO films on AZ91 Mg alloy were investigated under 1200 Hz of alternating current (AC) by voltage-time curves, in-situ observation of arc generation behavior and measurements of film thickness, surface roughness and micro vickers hardness. In the absence of Na₂SiO₃ in the 0.1 M NaOH + 0.05 M NaF solution, about 4 ㎛ thick PEO film was formed within 1 min and then PEO film did not grow but white spots were formed by local burning. Addition of Na₂SiO₃ up to 0.2 M caused more increased formation voltage and growth of PEO film with uniform generation of arcs. Addition of Na₂SiO₃ from 0.2 M to 0.4 M showed nearly the same voltage-time behavior and uniform arc generation. Addition of Na₂SiO₃ more than 0.5 M resulted in a decrease of formation voltage and non-uniform arc generation due to local burning. PEO film growth rate increased with increasing added Na₂SiO₃ concentration but maximum PEO film thickness was limited by local burning if added Na₂SiO₃ concentration is higher than 0.5 M. Surface roughness of PEO film increased with increasing added Na₂SiO₃ concentration and appeared to be proportional to the PEO film thickness. PEO film hardness increased with increasing added Na₂SiO₃ concentration and reached a steady-state value of about 930 H_V at more than 0.5 M of added Na₂SiO₃ concentration.

• 한국표면공학회지
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• 제46권3호
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• pp.116-119
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• 2013

To improve the corrosion resistance of an electrogalvanized steel sheet, we deposited magnesium film on it using a vacuum evaporation method and annealed the films at $250-330^{\circ}C$. The zinc-magnesium alloy is consequently formed by diffusion of magnesium into the zinc coating. From the anodic polarization test in 3% NaCl solution, the films annealed at $270-310^{\circ}C$ showed better corrosion resistance than others. In X-ray diffraction analysis, $ZnMg_2$ was detected through out the temperature range, whereas $Mg_2Zn_{11}$ and $FeZn_{13}$ were detected only in the film annealed at $310^{\circ}C$. The depth composition profile showed that the compositions of Mg at $270-290^{\circ}C$ are evenly and deeply distributed in the film surface layer. These results demonstrate that $270-290^{\circ}C$ is a proper temperature range to produce a layer of $MgZn_2$ intermetallic compound to act as a homogeneous passive layer.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.115-121
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• 2000

As the development of industry water quality of river is going to bad because of waste water of an industrial complex and general home agricultural chemicals exhaust of $SO_3$ and CO gas acid rain and so on. Corrosion damage of boiler factory equipment and so forth occur quickly due to using of the polluted water resulting in increasing leak accident. Especially working life of hot water boiler using the polluted water becomes more short and energy loss increases. The cathodic protection method is the most economical and reliable one to prevent corrosion damage of steel structures. Mg-base alloys galvanic anode protection of cathodic protection method is suitable for than application of hot water boiler using water with high specific resistance such as tap water. This paper is studied on the cathodic protection characteristics of how water boiler. In tap water and 0.001mol/$\ell$ NaCl solution the characteristics of anodic polarization of Mg-base alloys galvanic anode and tube material is investigated the measurement of cathodic protection potential according to the time elaspsed is carried out.

• 한국주조공학회지
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• 제13권4호
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• pp.359-368
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• 1993

Mg-9wt.%Al and Mg-9wt.%-1.6wt%Zn/SiCp(particle size $40{\mu}m$) metal-matrix-composite specimens were manufactured by rheo-compocasting method, known for its effect of improving the wettability. The ceramic reinforcement particles(SiCp) were dispersed in the semi-solid magnesium alloy matrix slurry being vigorously stirred in a high frequency induction furnace under inert atmosphere. A microstructural study of the dispersed particles in the specimens, prepared under different conditions as regards the time(10min, 20min, 30min) and temperature of the stirring, was made with the aid of optical microscope and SEM. The effect of superheating was also observed. It is revealed that 30 minutes' stirring time of the semi-solid at 40% solid fraction temperature(Mg-9wt.%Al : $590^{\circ}C$, AZ91 : $576^{\circ}C$), as determined by the lever rule, gives a satisfactorily uniform distribution of the particles. The superheating is observed to enhance further the uniformity.

• Journal of Welding and Joining
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• 제18권5호
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• pp.98-104
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• 2000

Aluminum alloys are being employed in automobile parts as strive to reduce overall vehicle weight to meet demands for improved fuel economy and reduction in vehicle emissions. Al-based composites reinforced with ceramic ($Al_2O_3,\;SiC,\;TiC\;and\;B_4C$) applications in a variety of components in automotive engines, such as liners, where the tribological properties of the material are important. In this study, Al-base composites reinforced with TiC particle powders has been developed for producing plasma spray coatings. The composite plasma spray powders were prepared Al-13Si-3Mg(wt%) alloy with TiC(40, 60 and 80wt%) particles ($0.2~5{\mu}textrm{m}$) by drum type ball milling. The composite powders ($36~76{\mu}textrm{m}$) were sprayed with plasma torch. Plasma sprayed coatings were heat-treated at $500^{\circ}C$ for 3 hours. The wear resistances of the plasma sprayed coatings were found to decrease with increasing TiC content and improved with heat treatment. AlSiMg-40% TiC heat-treated coatings were showed the best wear resistance in this study.

• 분석과학
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• 제7권4호
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• pp.517-526
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• 1994

Mn의 함량을 달리하여 제조한 Al-Li-Cu-Mg-Mn-Zr 합금의 미고용상 및 분산상을 EPMA(Electron Probe Microanalyzer)와 SAEM(Scanning Auger Electron Microscope)으로 분석하였다. 또한 미고용상의 부피 분율, 분포 및 형태를 광학현미경으로 관찰하였으며, 상온과 고온에서의 인장 특성을 조사하였다. Mn의 함량이 증가함에 따라 미고용상의 부피분율을 급격히 증가하고 연신율을 감소하였다. Mn은 기지 조직의 결정립을 미세하고 균일하게 분포하도록 하였다. 인장시험 결과, 0.44 wt% Mn이 첨가된 합금이 다른 합금보다 우수한 기계적 특성을 나타내었다.

• 한국주조공학회지
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• 제19권5호
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• pp.403-409
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• 1999

Mg-Zn-Zr ternary alloys containing 6wt% Zn and (0, 0.4, 0.6)wt% Zr, which is added for grain refinement, can be cast into complex shape by squeeze casting. The influence of Zn and Zr as additional elements on microstructure and mechanical characteristics is investigated by OM, SEM, WDX, XRD and microvickers hardness measurement. The microstructure of Mg-Zn-Zr alloys consists of primary ${\alpha}-Mg$ and MgZn eutectic compound between dendrites. The grain size is decreased from $136{\mu}m$ to $97\;{\mu}m$ by Zr addition, resulting in that the hardness is increased from 42Hv to 59Hv. Furthermore, the grain size is changed to $83{\beta}$ and the hardness is increased to 65Hv by additional infiltration pressure. These results indicate that the Zr addition and additional infiltration pressure are effective for grain refinement acting as an important factor to increase the hardness. The increment in hardness by the Zr addition is slightly larger than that by the additional infiltration pressure.

• 열처리공학회지
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• 제7권2호
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• pp.77-87
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• 1994

Roles of fundamental and additional hardening precipitates on the changes of mechanical properties and electrical resistivity during precipitation decomposition in binary Al-Li, ternaty Al-Li-Cu and multi-Li-Cu-Mg-Zr alloys have been investigated by the detailed measurement of electrical resistivity, hardness and tensile strength and the observation of transmission electron micrographs. Peek hardness and tensile strength in multi-component Al-Li-Cu-Mg-Zr Alloy had higher than that of the other alloys and the results of measurement of hardness, strength and electrical resistivity in each alloys aged at 90 and $190^{\circ}C$, precipitation behaviors and mechanical properties in binary, ternary and multi-component Al-Li alloys were contributed to the ${\delta}^{\prime}$ precursory phase of ${\delta}^{\prime}$, $T_1$, G.P.B. zone and S' phases, repectively.

• Journal of Magnetics
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• 제18권1호
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• pp.5-8
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• 2013

The perpendicular magnetic anisotropy of sputtered CoFeB thin films covered by MgO was investigated by vibrating sample magnetometry. Three different $Co_xFe_{80-x}B_{20}$ alloys were studied. Under out-of plane magnetic field, the saturation field was found to increase with increasing the Co content. The magnetization and interface anisotropy energy were obtained for all samples. Both showed a marked dependence on the MgO overlayer thickness. In addition, their variations were found to be non-monotonous as a function of the Co concentration.