• Transactions of Materials Processing
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• v.27 no.3
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• pp.160-164
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• 2018

The success of warm forming of Mg alloy sheets is very dependent on its frictional behavior at elevated temperatures. The effects of contact pressure and sliding length on the frictional characteristics of AZ31B Mg alloy sheet were investigated at elevated temperature and at room temperature. The contact pressure range for the friction test was determined through FE analysis of the roof panel which is a candidate for Mg alloy application. According to the experimental results, the frictional behavior of the Mg alloy sheet is equally highly influenced by both sliding length and contact pressure at room temperature. At elevated temperatures, however, the sliding length has a more dominant influence on the frictional characteristics of the Mg alloy sheet than the contact pressure, if the contact pressure is lower than a certain level.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.256-259
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• 2004

In the present study, AZ31B sheets has a bad formability in room temperature, but the formability is improved significantly as increasing the temperature because of rolled magnesium alloy sheet has a hexagonal closed packed structure (HCP) and a plastic anisotropy. In this paper, after tensile test in various temperatures, strain rate, show the tensile mechanical properties, yield and ultimate strength, K-value, work hardening exponent(n), strain rate sensitivity(m). As temperature increased, yield, ultimate strength and K-value, work hardening exponent(n) are decreased but strain rate sensitivity(m) is increased. As cross-head-speed increased, yield, ultimate strength and K-value, work hardening exponent(n) are increased. And according to the temperature, how change the plastic anisotropy factor R. In addition, we observed how temperatures and cross-head-speed effect on microstructure.

• Transactions of Materials Processing
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• v.22 no.8
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• pp.486-491
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• 2013

A numerical investigation of the butting process for an AZ31B magnesium alloy tube at elevated temperatures was conducted to develop a double-butted magnesium alloy tube. As a result of the current study, it was found that the amount of doming of the tube end, prior ironing-extrusion to obtain high wall thickness reduction are important factors for the butting process of magnesium alloy tubes. There is also a limitation of the thickness profile of butted tube due to buckling of tube wall during the stripping stage.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.246-249
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• 2007

This study is concerned with deep drawability of magnesium sheets(AZ31B) at the warm conditions. Especially the dependency on forming speed has been investigated at the temperature of $200^{\circ}C$ and $300^{\circ}C$. Deep drawing test has been carried out at the temperature of $200^{\circ}C$ and $300^{\circ}C$. The die and blank holder are kept at test temperature by local heating and the punch is kept at room temperature by cooling technique. The magnesium sheets called AZ31B with the thickness of 0.5mm have been applied to deep drawing of circular cup. The drawability has been estimated at the conditions of forming speed (0.1, 1, 10 mm/sec). The results of deep drawing experiments show that the drawability is better at $300^{\circ}C$. Also the deep drawability is improved at the low speed(1mm/sec).

• Transactions of Materials Processing
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• v.30 no.1
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• pp.43-48
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• 2021

The success of warm forming of Mg alloy sheet is greatly influenced by friction at elevated temperature, depending on the surface treatment of the tool. The tool coating affected the frictional characteristics of AZ31B Mg alloy sheet at elevated and room temperatures. The frictional behavior of the Mg alloy sheet at room temperature was not significantly affected by surface treatment conditions of the tool, but was significantly affected at elevated temperature. When the contact pressure is high, a few surface-treated tools exhibit a higher coefficient of friction than those without surface treatment. It is important to select the surface treatment conditions of the tool in order to ensure appropriate friction during warm forming of Mg alloy sheet.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.67-69
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• 2006

Since magnesium alloy has a limited formability at room temperature, forming should be carried out at the elevated temperature. If the initial grain size is small, superplasticity could be expected over $400^{\circ}C$. Using superplastic behavior, blow forming can be used to overcome the low formability of Mg alloys. In the present study, the optimization of blow forming of AZ31 alloy at the elevated temperature was investigated. Finite element simulation was carried out and verified with the blow forming experiments.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.118-121
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• 2005

The square cup drawing of magnesium alloy AZ31 $(aluminum\;3\%,\;Zinc\;1\%)$ sheets was studied by experimental approach in various temperatures (200, 250, 300, 350, $400^{\circ}C$) when blank holding force (BHF) was controlled in real-time. And so on, the drawability was measured with the different die and punch coating. The square cup drawing test was performed by three different coated punches (CrN, TiCN, Non-coated). BHF was set about 2.0 KN, forming speed was 50 mm/min, blank thickness were 0.5, 1.0mm and the cup size was 40 mm by 60 mm after forming. The experimental data of square cup drawing test show that the tools coating and temperature were effect on the drawbility.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.71-71
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• 2013

AZ31 마그네슘 합금 판재는 경량화가 요구되는 분야에 사용되는 것을 목표로 설계되어 상업화가 추진되고 있으며, 이의 적용을 위해서는 마그네슘 판재의 내 부식성을 제어하는 표면처리 공정이 필수적이다. 표면처리에서는 강판 및 알루미늄판재의 표면처리 공정에 이용되는 화성처리-전착도장 공정에 따라야 하겠지만, 산 용액에 매우 취약한 마그네슘 소재의 특성상 같은 처리 조건을 적용하기 어렵다. 산 종류에 따른 AZ31 마그네슘합금판재 표면처리효과를 알아보기 위해 여러 종류의 산 처리 후 내 부식성을 알아보고 HH(Heat and Humidity; 가압, 가습 조건에서 열처리) 공정을 접목시킨 표면처리 결과에 대하여도 관찰하였다. 그 중 불산을 이용한 표면처리는 농도별로 진행하여 산세의 농도가 표면에 주는 영향에 대하여도 알아보았다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.64-68
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• 2005

In recent years, there has been a growth of the manufacture and application of magnesium products because of its small specific gravity as well as its relatively high strength. However, there are so many studies to assure good formability because magnesium sheet alloy is difficult to form. In this study, uniaxial tensile and biaxial tensile test of AZ31 magnesium sheet alloy with thickness of 1.2mm were performed at room temperature. Uniaxial tensile test were performed until $7\%$ of engineering strain. R-values and stress-strain curve were obtained. Biaxial tensile tests with cruciform specimen were performed until the breakdown of the specimen occurs. The yield loci are made by application of plastic work theory. The results are compared with the theoretical predictions based on the Hill and Logan-Hosford model. However, next study will be performed at warm-temperature because the specimens are broken under the $0.5\%$ of equivalent strain at biaxial tensile test.

• Transactions of Materials Processing
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• v.14 no.7 s.79
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• pp.628-634
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• 2005

The drawability of AZ31B magnesium sheet is estimated at various temperatures (200, 250, 300, 350, $400^{\circ}C$), forming speeds (20, 50, 100mm/min), thicknesses (0.8, 1.4mm) and blank holding forces (2.0, 2.8, 3.4kN). The deep drawing process (DDP) of circular cup is used in forming experiments. The results of deep drawing experiments show that the drawability is well at the range from 250 to $300^{\circ}C$, 50mm/min forming speed and 2.0kN blank holding force. The 0.8mm magnesium sheets were deformed better than 1.4 mm. Blank holding force was controlled in order to improve drawability and prevent the change of cup thickness. When blank holding force was controlled, tearing and thickness change were decreased and limit drawing ratio was improved from 2.1 to 3.0.