• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.85-89
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• 2010

The plastic deformation behavior of magnesium alloy is affected simultaneously by deformation temperature and strain rate under warm and/or hot working conditions. The soundness of deformation of AZ31-xCa (x=0. 0.7, 2.0 wt.%) extrudes during compression was strongly affected by processing variables including deformation temperature, strain rate. compression-loading direction, which was related to the activation of available deformation systems. The deformation behavior of AZ31-xCa extrudes was also affected by Ca content, which was related to the change of the sort and fraction of second phase. The complex effects of deformation temperature and strain rate on the deformation behavior of AZ31-xCa extrudes during compression under various conditions could be successfully described by Zener-Hollomon parameter.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.225-230
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• 2016

Effect of electrolyte composition and concentration on PEO coating layer were investigated. Mg alloy, Surface of AZ31 and AZ91 were oxidized using PEO with different electrolyte system, Na-P and Na-Si. and applied voltage and concentration. We measured thickness, roughness, X-ray crystallographic analysis and breakdown voltage of the oxidized layer. When increasing concentration of electrolyte, the thickness of oxide layer also increased too. And roughness also increased as concentration of electrolyte increasing. Breakdown voltage of coated layer showed same behavior, the voltage goes high as increasing thickness of coating layer, as increasing concentration of electrolyte, and increasing applied voltage of PEO. $Mg_2SiO_4$ phase were observed as well as MgO.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.62-65
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• 2008

Extrusion characteristics of Mg alloys were studied experimentally. The Al-Zn-Mg alloys, AZ31, AZ6l, AZ80, and AZ91 were extruded with hot hydrostatic extrusion process. The hydrostatic process was efficient to reduce surface friction and extend steady state region in extrusion which made it more convenient to examine deformation behavior of the alloys avoiding the disturbance caused by temporary contact state between billet and die, and billet and container. High pressure was cooperative to expand forming limit of the alloys which were applied on the billet during the extrusion process. Extrusion limits were traced in temperature and extrusion speed domain with changing composition of the alloying elements. Effects of process parameters on extrusion load and microstructure evolution were investigated also.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.139-146
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• 2011

In present study, it aims to compare the noise and vibration characteristics between magnesium alloy and steel hood panel. The AZ31 magnesium hood panel was fabricated through warm forming process, and the noise and vibration characteristics between both hood panels was compared through the measurement of engine radiation noise and transmission loss, as well as FRF on modal analysis. The sound insulation performance of magnesium alloy was wholly superior to that of steel hood panel, even though the transmission loss of magnesium alloy is lower than that of steel due to mass effect primarily. The FRF characteristics on modal analysis indicates that the resonance frequency of magnesium hood panel is remarkably increased to higher value than that of steel hood panel. The radiation and interior noise of magnesium panel even without acoustic hood insulation were remarkably lower than those of steel hood panel with acoustic insulation, in particular, at a range below 4,000 rpm.

• Corrosion Science and Technology
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• v.20 no.4
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• pp.175-182
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• 2021

Magnesium alloy is limited in the industrial field because its standard electrode potential is -2.363 V vs. NHE (Normal Hydrogen Electrode) at 25 ℃. This high electrochemical activity causes magnesium to quickly corrode with oxygen in air; chemical conversion coating prevents corrosion but causes surface defects like cracks and pores. We have examined the anti-corrosion effect of sol-gel coating sealed on the defected conversion coating layer. Sol-gel coatings produced higher voltage current and smaller pore than the chemical conversion coating layer. The conversion coating on magnesium alloy AZ31 was prepared using phosphate-permanganate solution. The sol-gel coating was designed using trimethoxymethylsilane (MTMS) and (3-Glycidyloxypropyl) trimethoxysilane (GPTMS) as precursors, and aluminum acetylacetonate as a ring-opening agent. The thermal shock resistance was tested by exposing specimens at 140 ℃ in a convection oven; the results showed changes in the magnesium alloy AZ31 surface, such as oxidization and cracking. Scanning electron microscope (FE-SEM) analysis confirmed a sealed sol-gel coating layer on magnesium alloy AZ31. Electrochemical impedance spectroscopy (EIS) measured the differences in corrosion protection properties by sol-gel and conversion coatings in 0.35 wt% NaCl solution, and the potentiodynamic polarization test and confirmed conversion coating with the sol-gel coating show significantly improved resistance by crack sealing.

• Korean Journal of Materials Research
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• v.32 no.7
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• pp.326-331
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• 2022

AZ31 magnesium alloy was used to manufacture a thin plate using a melt drag method. The effects of roll speed, molten metal temperature, and molten metal height, which are the basic factors of the melt drag method, on the surface shape, the thickness of the thin plate, Vickers hardness, and microstructure of the thin plate were investigated. It was possible to manufacture AZ31 magnesium alloy thin plate at the roll speed range of 1 to 90 m/min. The thickness of the thin plate, manufactured while changing only the roll speed, was about 1.8 to 8.8 mm. The shape of the solidified roll surface was affected by two conditions, the roll speed and the molten metal height, and the Vickers hardness of the manufactured magnesium alloy thin plate value ranged from Hv38~Hv60. The microstructure of the thin plate produced by this process was an equiaxed crystal and showed a uniform grain size distribution. The grain size was greatly affected by the contact state between the molten metal and the solidification roll, and the amount of reactive solids and liquids scraped at the same time as the thin plate. The average grain size of the thin plate fabricated in the range of these experimental conditions changed to about 50-300 ㎛.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.75-80
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• 2012

In this study, we are aimed to prevent grain growth of semi-solid AZ31 magnesium alloys during reheating process. The semi-solid AZ31+(Ca) billets were investigated by using metallographic analysis, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy in order to elucidate the effect of Ca addition during reheating process. The grain growth of semi-solid AZ31+(Ca) billet was reduced with increasing Ca content during reheating. The grain size of AZ31+(Ca) billet decreased with increasing volume fraction of Al2Ca particles. The grain growth rate constant K calculated by Oswald ripening LSW theory in AZ31+1.5wt.% Ca billet was the lowest 129.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.597-602
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• 2006

Bulk plastic forming characteristics were studied for the magnesium alloy, AZ31 in warm backward extrusion. Effects of process conditions such as extrusion ratio, forming temperature, and punching speed were investigated respectively. Variation of microstructure induced by the warm backward extrusion process was observed. Microstructure of the work piece showed evidences of recrystallization under the experiment conditions. It is estimated that in specific punch speed region fast stroke accelerates recrystllization and reduces the forming load.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.190-190
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• 2015

본 연구에서는 AZ31 마그네슘 합금의 내식성을 향상시키기 위하여 플라즈마 전해산화(PEO, plasma electrolytic oxidation)법을 이용하여 다양한 용액에서 양극 및 음극 펄스전류를 인가하여 형성하였다. PEO피막 내부에 형성된 기공의 모양 및 크기를 에폭시 레플리카법을 이용하여 관찰하였다. PEO 피막 내부의 기공의 크기는 용액의 pH가 증가할수록 작아졌으며 균열의 크기는 증가하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.98-98
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• 2012

마그네슘 합금판재 사용을 위한 표면처리 중 화성처리는 합금판재 표면에 화학적 반응을 유도하여 산화막 또는 무기염 형태의 얇은 피막을 형성시켜 표면 물성을 향상시키는 방법으로, 본 발표에서는 화성처리된 AZ31 마그네슘 합금 판재의 표면의 지속성을 평가하기 위한 시험을 진행하고 그 결과를 소개하였다.