• Korean Journal of Materials Research
• /
• v.8 no.8
• /
• pp.672-677
• /
• 1998

The following work examines the growth rate and microstructure of the $AI_2O_3$-composite formation by melt oxdation of pentad AI-alloys. The I weight % of each metal elements Cu and Ni were added to AI-IMg-3Si-3Zn and AI-IMg- 3Si-5Zn alloys. The diffenent pentad AI-alloys were oxidized 20 hours long at 1373K and 1473K. The oxidation rates were determined by observing the weight gain. The macro- and microstructure of formed oxide layer were examined by optical microscopy. The AI-IMg-3Si-5Zn-lCu alloy revealed the best oxidation behavior, but formedoxide layer was inhomogeneous.The oxidation rate were accelerated, and the uniform growth of the oxide layer with fine microstructure were obtained by putting a thin layer of $SiO_2$ on the surface of the alloy.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2010.05a
• /
• pp.46.2-46.2
• /
• 2010

최근 수송기기 및 전자부품산업에서의 성능향상 요구에 따라 경량고강도 비철금속재료의 수요가 증대되고 있다. 특히, 세계적으로 에너지 절약 및 환경 공해 규제가 대폭 강화됨에 따라 자동차, 항공기 등 수송기기의 소재경량화 소재로 낮은 밀도 기계적 가공성이 우수한 마그네슘 합금이 각광을 받고 있다. 그러나 Mg합금은 알루미늄 합금과는 달리 보호성 산화피막이 형성되지 않아 내식성 및 고온강도가 매우 취약하다. 이를 보안하기 위해서 본 연구에서는 마그네슘의 강도 개선을 위한 원소로써 고용강화 원소로 많이 쓰이는 Zn과 입자 미세화로 인한 항복강도를 증가시키는 Mn의 3원계 합금에 고온에서 안정한 Mg2Sn상이 형성되는 Sn을 첨가하여 시효처리에 따른 기계적 특성과 미세조직을 관찰하였다. 실험 이전에 Pandat Program에 의한 열역학적 분석을 바탕으로 Mg-Zn-Mn 및 Mg-Zn-Mn-Sn의 상태도 계산 및 MgZn와 Mg2Sn 석출분율을 예측하였다. 열역학 계산을 통해 도출된 석출온도를 통해 Mg-Zn-Mn 및 Mg-Zn-Mn-Sn 합금의 열처리에 따른 경도 및 미세구조를 관찰하였다. 또한, 기계적 특성을 평가하기 위해 상온 및 고온 인장시험을 실시하였고 XRD, SEM을 이용하여 석출상을 분석하였다.

• Journal of Power System Engineering
• /
• v.10 no.3
• /
• pp.45-50
• /
• 2006

In this paper, creep tests of Mg-Zn-Mn and Mg-Zn-Mn-Ca alloy casted by mold under the temperature range of 473.00-573.00K, and the stress range of 23.42-87.00Mpa were done with the equipment of automatic controlled temperature and computer for data acquisition. The activation energies were obtained by relationship between creep rate and temperature, and the stress exponents were obtained by relationship between creep rate and stress. From the experiment results, the activation energies of Mg-Zn-Mn and Mg-Zn-Mn-Ca alloy were 149.87kJ/mol, 147.97kJ/mol, respectively, and the stress exponents of those alloy were 5.13, 5.59, respectively, under the temperature of 473.00-493.00K and the stress range of 62.43-78.00Mpa. And the activation energies of those alloy were 134.41kJ/mol, 129.22kJ/mol, respectively, and the stress exponent of those alloy were 3.48, 3.77, respectively, under the temperature of 553-573Mpa and the stress range of 23.42-39.00Mpa. Also the lifes of Mg-Zn-Mn-Ca alloy were higher than those of Mg-Zn-Mn alloy, and the results of SEM showed fracture surfaces under low temperature had smaller dimples than those under high temperature.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2014.05a
• /
• pp.94-95
• /
• 2014

The purpose of this study is to evaluate the corrosion protective property of Al-Mg high-freqeuncy arc metal spray method in comparison to Zn-Sn and Zn-Al alloys by electrochemical method and CASS test. As a result, it appeared that Al-Mg alloy had very higher corrosion protective property through the electrochemical characteristic and the CASS test comparing with the other alloys.

• Korean Journal of Materials Research
• /
• v.5 no.6
• /
• pp.682-689
• /
• 1995

In order to refine the grain size of Mg-Zn alloy 0.5 to 6wt.%Cu or Si elements were added. Alloy ingot was made under vacuum atmosphere of 4 ${\times}$ 10$\^$-4/ Torr in the quartz tube coated by BN. Grain size and hardness were measured after solution treatment for 8 hours at 435$^{\circ}C$. Optimal condition for grain size refining effect was obtained at the minimum composition of 2wt.%Cu or 1.5wt.%Si addition to Mg-6wt%Zn alloy. Age hardening behavior was experimented at the optimal compositions of the Mg-6wt.%Zn, Mg-6wt.% Zn-2wt.%Cu and Mg-6wt.% Zn-1.5wt.%Si. The hardness increment due to fine grain size was higher at the Mg-Zn-Cu alloy system, but that due to age hardening was higher at the Mg-Zn-Si alloy system.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.10 no.6
• /
• pp.83-88
• /
• 2011

Magnesium alloys have been focussed for the applications for lightweight of vehicle and electronics due to their high strength, low specific density and good damping capacity. This paper deals with the creep strength of Mg-Nd-Zr-Zn alloy. For the alloy, pure magnesium(99.9%) was melt with atmosphere of $0.3%SF_6$ and $25%CO_2$. After melting, 0.3% of zinc was inserted to stir for 10min at elevated temperature of $770^{\circ}C$. Master alloys of Mg-15%Nd and Mg-15%Zr were stirred in furnace. The creep tests were performed to obtain creep rate and rupture in the temperature range of 200 to $220^{\circ}C$ and 280 to $310^{\circ}C$ at an applied stress of 156 to 172MPa and 78 to 94MPa, respectively. The deformation mechanism was predicted dislocation climb from measured apparent activation energy and stress exponent. Also the increaser the temperature and stress the lower the stress exponent and activation energy. Finally, LMP parameter gives good information for the predicted creep rupture life.

• Journal of Korea Foundry Society
• /
• v.35 no.3
• /
• pp.53-61
• /
• 2015

Effects of Zn addition on the microstructure and corrosion behavior of Mg-8%Al-(0-1)%Zn casting alloys were investigated. With increasing Zn content, the amount of ${\beta}(Mg_{17}Al_{12})$ phase increased, while ${\alpha}$-(Mg) dendritic cell size became reduced. The corrosion rate decreased continuously with the increase in the Zn content. The evaluation of the microstructural evolution indicates that the improved barrier effect of ${\beta}$ particles formed more continuously along the dendritic cell boundaries and the incorporation of more ZnO into the surface corrosion product, by which the absorption of $Cl^-$ ions is impeded, are responsible for the better corrosion resistance in relation to the Zn addition.

• Journal of Powder Materials
• /
• v.15 no.2
• /
• pp.95-100
• /
• 2008

The investigation is to modify the mechanical and chemical properties of Mg alloys using a combination of rapid solidification and surface treatment. As the first approach, $Mg_{95}Zn_{4.3}Y_{0.7}$ was gas atomized and pressure sintered by spark plasma sintering process (SPS), showing much finer microstructure and higher strength than the alloys as cast. Further modification was performed by treating the surface of PM Mg specimen using Plasma electrolytic oxidation (PEO) process. During the PEO processing, MgO layer was initiated to form on the surface of Mg powder compacts, and the thickness and the density of MgO layer were varied with the reaction time. The thickening rate became low with the reaction time due to the limited diffusion rate of Mg ions. The surface morphology, corrosion behavior and wear resistance were also discussed.

• Journal of Korea Foundry Society
• /
• v.29 no.6
• /
• pp.265-269
• /
• 2009

The optimum RRA heat treating conditions and SCC (stress corrosion cracking) resistance of semi-solid Al-Zn-Mg-Cu alloy fabricated by inclined cooling plate were compared with those of conventional mould cast alloys. The non-stirring method characterized by using a cooling plate can effectively eliminate dendritic structure and form a fine globular semisolid microstructure in as-cast Al-Zn-Mg-Cu alloy and the SCC resistance of semi-solid Al-Zn-Mg-Cu alloy was higher than that of conventional mold cast alloy. Also, after retrogressed treatment at RRA heat treatment of semi-solid Al-Zn-Mg-Cu alloy, retrogressed treatment time has increased more than 10 minutes at $180^{\circ}C$ to recovery the T6 heat treatment strength.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.8
• /
• pp.602-607
• /
• 2013

Concern for the TOS (Transparent Oxide Semiconductor) is increasing with the recent increase in interest for flexible device. Especially MgZnO has attracted a lot of attention. $Mg_xZn_{1-x}O$, which ZnO-based wideband-gap alloys is tuneable the band-gap ranges from 3.36 eV to 7.8 eV. In particular, the flexible substrate, the crystal structure of the amorphous as well as the surface morphology is not good. So research of MgZnO thin films growth on flexible substrate is essential. Therefore, in this study, we studied on the effects of the oxygen partial pressure on the structural and crystalline of $Mg_{0.1}Zn_{0.9}O$ thin films. MgZnO thin films were deposited on PES substrate by using pulsed laser deposition. We used XRD and AFM in order to observe the structural characteristics of MgZnO thin films. UV-visible spectrophotometer was used to get the band gap and transmittance. Crystallization was done at a low oxygen partial pressure. The crystallinity of MgZnO thin films with increasing temperature was improved, Grain size and RMS of the films were increased. MgZnO thin films showed high transmittance over 80% in the visible region.