• Design & Manufacturing
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• 제2권6호
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• pp.43-48
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• 2008

Magnesium alloys have given high attention to the industry of light-weigh as automobile and electronics with aluminium, titanium and composite alloys due to their high strength, low specific density and good damping characteristics. But the magnesium contained structures under high temperature have the problems related to creep deformation and rupture life, which is a reason of developing the new material against creep deformation to use them safely. The purpose of this study is to predict the creep deformation mechanism and rupture time of AZ31 magnesium alloy. For this, creep tests of AZ31 magnesium alloy were done under constant creep load and temperature with the equipment including automatic temperature controller with acquisition computer. The apparent activation energy Qc, the applied stress exponent n and rupture life have been determined over the temperature range below 0.5Tm and stress range of 109~187MPa, respectively, in order to investigate the creep behavior. AZ31 Magnesium alloy identify the activation energy for creep deformation and the stress dependence to creep rate at below 0.5Tm, and then investigate the mechanism for creep deformation and creep rupture life of AZ31 Magnesium alloy.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.231-234
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• 2005

The high temperature deformation behavior of AZ 31 Mg alloy was investigated by designing a back propagation neural network that uses a gradient descent-learning algorithm. A neural network modeling is an intelligent technique that can solve non-linear and complex problems by learning from the samples. Therefore, some experimental data have been firstly obtained from continuous compression tests performed on a thermo-mechanical simulator over a range of temperatures $(250-500^{\circ}C)$ with strain rates of $0.0001-100s^{-1}$ and true strains of 0.1 to 0.6. The inputs for neural network model are strain, strain rate, and temperature and the output is flow stress. It was found that the trained model could well predict the flow stress for some experimental data that have not been used in the training. Workability of a material can be evaluated by means of power dissipation map with respect to strain, strain rate and temperature. Power dissipation map was constructed using the flow stress predicted from the neural network model at finer Intervals of strain, strain rates and subsequently processing maps were developed for hot working processes for AZ 31 Mg alloy. The safe domains of hot working of AZ 31 Mg alloy were identified and validated through microstructural investigations.

• 열처리공학회지
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• 제17권4호
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• pp.230-235
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• 2004

Present work was carried out to investigate the influence of welded conditions, such as welding current, diameter of welding wire on the microstructural change and mechanical properties of TIG welded joint in AZ31B Mg alloy. It was found that good and sound welded joint was achieved in all welding conditions. The grain size decreased with increasing welding current and decreasing diameter of welding wire. Also, the second phases were homogeneously distributed in the grain and grain boundary as decreasing welding current and diameter of welding wire. The ${\beta}$ discontinuos precipitates were observed in the welded joint, but this microstructure has not been reported by previous researchs in AZ31B Mg alloy. The hardness value is affected by the existence state of the second phase and the hardness of the welded joint region is lower than the other regions in welded AZ31B Mg alloy. The strength of the welded joint region was influenced by the grain size and has more than 90%, compared to that of ASTM standard specification.

• 한국표면공학회지
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• 제49권4호
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• pp.331-338
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• 2016

In this work, anodic oxidation behavior of AZ31 Mg alloy was studied as a function of $Na_2CO_3$ concentration in electrolyte by voltage-time curves and observation of surface appearances and morphologies after the anodic treatments, using optical microscopy and confocal scanning laser microscopy (CSLM). The voltage-time curves of AZ31 Mg alloy surface and surface appearances after the anodic treatments showed three different regions with $Na_2CO_3$ concentration : region I, below 0.2 M $Na_2CO_3$ where shiny surface with a number of small size pits; region II, between 0.4 M and 0.6 M $Na_2CO_3$ where dark surface with relatively low number of large size burned or dark spots; region III, more than 0.8 M $Na_2CO_3$ where bright surface with or without large size dark spots were obtained. The anodically treated AZ31 Mg alloy surface became significantly brightened with increasing $Na_2CO_3$ concentration from 0.5 M to 0.8 M which was attribute to the formation of denser and smoother surface films. Pits and porous protruding reaction products were found at relatively large size and small size spots, respectively, on the AZ31 Mg alloy surface in low concentration of $Na_2CO_3$ less than 0.2 M. The formation of pits is attributed to the result of repetition of the formation and detachment of porous anodic reaction products. Based on the experimental results obtained in this work, it is concluded that more uniform, denser and smoother surface of AZ31 Mg alloy could be obtained at more than 0.8 M $Na_2CO_3$ concentration if there is no other oxide forming agent.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 추계학술대회 논문집
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• pp.189-190
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• 2007

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.222-222
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• 2009

• 한국융합학회논문지
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• 제12권5호
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• pp.17-22
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• 2021

환경 친화적인 마그네슘-공기 전지는 이론적 방전용량이 매우 높은 1차전지로 알려진 금속-공기 전지이며 대기 중 산소를 양극 활물질로 사용하고 마그네슘 합금을 연료로 사용하는 관점에서 금속-연료전지로도 불리고 있다. 음극으로 사용하는 마그네슘합금의 성능에 따라 전지 전체 성능이 결정되므로 고성능 전지로 상용화하기 위해서는 음극 재료인 마그네슘 합금 전극의 성능에 대한 연구와 개선이 필요하다. 본 연구는 상용화된 마그네슘 합금(AZ31, AZ61)을 선택하여 마그네슘-공기 전지용 전극재료로서 가능성을 평가하기 위하여 전기화학적인 측정을 실시하고 방전 특성을 조사하였다. 개방회로전위 변화, Tafel 곡선 변화, 순환전류전압곡선 측정을 통해 마그네슘합금들의 전기화학적 특성을 조사하였고 정전류 방전 실험을 통해 AZ61 합금의 우수한 방전 용량(1410mAhg^-1)과 가능성을 평가하였다.

• 소성∙가공
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• 제21권7호
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• pp.403-411
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• 2012

The aim of this study was to predict the results of superplastic forming on magnesium alloy, by considering the grain growth using numerical simulations. Superplastic behavior of AZ31 alloy was investigated through a set of uniaxial tensile tests that cover the forming temperatures ranges from 375 to $450^{\circ}C$. All the material parameters in the model, which consists of a constitutive equation and a grain growth equation, were determined. The model was used in the finite element analysis for uniaxial tensile tests and superplastic blow forming, through a user-subroutine available within ABAQUS. From this study, the effect of grain growth during forming was evaluated. The results show that it is essential to include the effect of grain growth in predicting the behavior during superplastic forming of this magnesium alloy.

• 동력기계공학회지
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• 제15권1호
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• pp.39-44
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• 2011

This study was to investigate the effects of stress ratio and anisotropy on Fatigue Crack Propagation(FCP) behavior of rolled magnesium alloy AZ31B. The experimental materials were a Mg-Al-Zn magnesium alloy. The FCP test was conducted on compact tension specimen by a servo-hydraulic fatigue testing machine in air at room temperature. Compact tension specimens were prepared from the extruded parallel and vertical rolling direction. The test condition was frequency of 10Hz and sinusoidal load stress ratios are 0.1 and 0.7. The FCP rates was automatically measured by a compliance method. In the case of the FCP of AZ31B, the FCP of both direction of LT and TL by anisotropy of specimens are almost same value. In lower stress ratio, the FCP of the LT, TL specimens are increased in lower ${\Delta}K$ region but higher ${\Delta}K$ regions are almost same value. Finally, the result of observed the surface crack, it expressed the quasi-cleavage fracture in lower ${\Delta}K$ region and straight mark on the aspect of the facet in high ${\Delta}K$ region.

• 한국표면공학회지
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• 제51권6호
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• pp.405-414
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• 2018

The present study investigated the adhesion and corrosion resistance of subsequent electrophoretic paint (E-paint) on "electroless" paint coated AZ31 Mg alloy, which was formed by immersion of AZ31 Mg alloy in E-painting solution. It was found that with increasing immersion time of AZ31 in E-painting solution, the amount of paint deposited by electroless process increased but it decreased the electrochemical equivalent of E-painting process and the adhesion of the subsequent E-paint layer. The E-paint on electroless paint coated AZ31 contained pores with the highest pore density and the largest pore size was obtained on the samples with electroless times of 2 and 5 minutes, respectively. Results of the salt-spray test showed an accelerated growth of blisters over the entire surface of the sample immersed for less than 5 minutes whereas blisters were observed only in the vicinity of the scratch in case of samples treated for 15 and 30 minutes. The E-paint on AZ31 with shorter electroless immersion time in E-painting solution was found to have good adhesion and better corrosion resistance.