• Laser Solutions
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• v.15 no.3
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• pp.11-15
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• 2012

The laser weld of AZ31 magnesium alloy was characterized with OM, EBSD and micros vickers hardness tester in experiment. EBSD analysis and micro-hardness measurements were carried out at the three regions (Equiaxed Zone, Columnar Dendrite Zone, Base Metal) of the welded AZ31Mg alloy sheets. The magnesium alloy show the rectangular shape bead in laser weld. EBSD analysis revealed that the three regions show the heterogeneous distribution of grain size and microtexture. Micro-hardness measurement also revealed that the heterogeneous distribution of microstructure contributed to the heterogeneous micro-hardness distribution in the three regions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.235-238
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• 2005

In this study, it is investigated that the effect of material properties such as strength coefficient and strain hardening exponent on formability of AZ31 alloy sheet in square cup deep drawing process. Mechanical properties of AZ31 alloy sheet at elevated temperature $250^{\circ}C$ are obtained from uniaxial tensile tests and based on these results, a series of square cup deep drawing tests at the same temperature condition are carried out. Also, the possibilities of necking initiation is predicted by the FEM and FLD and compared with experimental results.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.268-268
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• 2015

The corrosion protection behavior of AZ31 magnesium alloy (Mg alloy) with cathodic electrophoretic coating (E-coating) pretreated by cerium-based conversion coatings at various pH was investigated in this study. Cerium-based conversion coatings (CeCCs) were deposited on AZ31 Mg alloy by immersion treatment in the nitrate-based cerium salt solution. The morphology and composition of the CeCCs were analyzed using scanning electron microscopy and energy dispersive X-ray spectroscopy. The corrosion properties of the AZ31 Mg alloy pretreated with cerium coating and subsequently E-coated were studied during salt-spray testing. The surface morphologies of the E-coated Mg alloy were examined in detail after different testing times using digital photography. It was found that the protective properties of the E-coating on AZ31 Mg alloy generated are heavily dependent upon the CeCC factors such as treatment time, coating thickness and pH of the solution.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.60-63
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• 2007

The effect of process parameters on springback of AZ31B magnesium alloy sheet was investigated by performing 2D draw bending test at the elevated temperatures. And also the springback characteristics were studied different blank holding forces between 30 to 250 kgf. Springback was considerably reduced at higher temperatures than $200^{\circ}C$. The blank holding force in the range used, however, had little influence on springback in isothermal tests. For a given temperature, springback decreased with increasing blank holding force in non-isothermal tests.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.45-45
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• 2011

마그네슘 합금은 상용 구조용 합금 중에서 비중이 1.74로 가장 낮아 경량화가 요구되는 분야에서 오랫동안 각광을 받아왔다. 그러나 마그네슘 합금은 상용 금속들 중에서 가장 화학적 활성이 커서 표면처리 후 내식성 확보가 필수적이다. 기존의 마그네슘 합금의 표면처리 방법은 주로 AZ91D의 다이캐스팅재에 집중되어 왔으며, 포스코에서 생산되는 AZ31의 스트립 캐스팅재의 표면처리는 합금의 차이로 인하여 공정이 새롭게 개발되어야 한다. 본 연구에서는 화성처리 공정에서 AZ31, AZ61, AZ91D의 합금 차이에 의한 화성피막의 특성을 고찰하였다.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.141-146
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• 2016

In this study, electrophoretic paint (E-paint) was deposited on the knife-abraded surface of AZ31 magnesium alloy (AZ31), and its adhesion and corrosion resistance were examined by tape peel-test and salt spray test, respectively. E-paint started to deposit on AZ31 Mg alloy after an inductance time and pores were found in the E-paint layer which is ascribed to hydrogen bubbles generated on the surface during the painting process. The pores disappeared after curing for 15 min at $160^{\circ}C$. The E-paint on AZ31 exhibited good adhesion after immersion in deionized water for 500 h at $40^{\circ}C$. The E-paint sample without scratch showed no corrosion after 1500 h of salt spray test. However, on the scratched sample, blisters were visible adjacent to the scratched sites after 500 h of salt spray test.

• Journal of the Korean institute of surface engineering
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• v.55 no.4
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• pp.196-201
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• 2022

This paper deals with anodic oxidation behavior of AZ31 Mg alloy in aqueous solutions containing various NaF concentrations from 0.01 M to 1 M. Three different voltage-time curves and anodic oxide formation behaviors appeared with concentration of NaF in deionized water. When NaF concentration is lower than 0.02 M, the voltage of AZ31 Mg alloy increased linearly and then reached a steady-state value more than 200 V, and large size pits and thin oxide layer were formed. When NaF concentration is between 0.05 M and 0.1 M, the voltage of AZ31 Mg alloy showed large periodic fluctuations of about 30 ~ 50 V around more than 200 V and large number of small particles were observed. If NaF concentration is higher than 0.2 M, PEO films can be formed without visible arcs under solution pH 6.5 ~ 7.5 by F^- ions without help of OH^- ions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.452-455
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• 2008

In the present study, blow forming characteristics of commercially roiled AZ31 alloy sheets were investigated. Two different kinds of AZ31 sheets were originally fabricated by using direct casting and strip casting methods respectively. Both sheets have similar grain sizes of about $7{\mu}m$ with a relatively equiaxed structure after rolling. A series of tensile tests were carried out to get flow behavior in terms of temperature and strain rate. Also, grain size effect was investigated by annealing as-received sheet at elevated temperatures. Elongation increased with temperature increment as well expected. However, the differences in tensile test condition did not give much difference in elongation even at the temperature range where a large elongation would be expected with such as fine grain of $7{\mu}m$. Blow forming experiments showed that forming condition did not result in higher difference in dome height. However, the interesting feature from this study was that formability of this AZ31 alloy got different with stress condition. Firstly, biaxial stress condition might result in lower temperature and strain rate dependencies compared to uniaxial tension results for both DC and SC sheets. Secondly, DC showed slower grain growth in uniaxial tension than in biaxial stress state while SC has much higher grain growth rage in uniaxial tension than in bulging.

• Design & Manufacturing
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• v.2 no.6
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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.

• Journal of Power System Engineering
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• v.15 no.1
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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.