• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.172-172
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• 2012

Mg합금은 지극히 열악한 내산화성을 갖는 MgO로 산화되기 때문에, 모든 Mg합금은 고온에서는 쉽게 산화되고 발화된다. 그러나, CaO를 첨가하면 CaO가 시편의 노출면적을 줄이고, 산소의 내부확산을 억제함으로써 시편 표면에 얇고 균일한 보호피막을 형성하여 Mg합금의 산화 저항성을 증가시켰다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.594-599
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• 2011

In this paper, the effect of the boundary conditions on the reliability and the cumulative distribution characteristics of the fatigue failure life is analyzed in a magnesium alloy AZ31. The boundary conditions are specimen thickness, stress ratio, and maximum fatigue load. The statistical data of the fatigue failure life are obtained by fatigue crack propagation tests under the detail conditions for each boundary condition. The 3-parameter Weibull distribution is used to analyze a statistical characteristics of the fatigue failure life in magnesium alloy AZ31. It is found that the statistical fatigue failure life is long in the case of a thicker specimen, a larger stress ratio, and a smaller maximum fatigue load. Under the opposite cases, the reliability on the fatigue failure life is rapidly dropped.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.374-377
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• 2008

Magnesium alloy sheets are usually formed at temperatures between $150^{\circ}C$and $300^{\circ}C$ because of their poor formability at room temperature. In the present study, the formability of AZ31B magnesium alloy sheets was investigated by the analytical and experimental approaches. First, tensile tests and the limit dome height test were carried out at elevated temperatures to get the mechanical properties and forming limit diagram, respectively. And then deep drawing of cross shaped die was tried to get the minimum corner radius and forming limit at specific temperature. Blank shape, punch velocity, minimum corner radius, fillet size, etc, were determined by finite element analysis physical try-outs. Especially, optimum punch and die temperature were suggested through the temperature-deformation analysis using Pam-stamp.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.646-652
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• 2014

It is the primary aim of this paper to propose the empirical fatigue crack propagation model fit to describe a crack growth behavior of AZ31 magnesium alloys under the different specimen thickness conditions. The empirical models estimated are Paris-Erdogan model, Walker model, Forman model, and modified-Forman model. The parameters of each model are estimated by maximum likelihood method. The statistical crack growth data needed for an estimation of empirical models are obtained by fatigue crack propagation tests under the three cases of specimen thickness. It is found that the good empirical models fit to describe a crack growth behavior of AZ31 magnesium alloys under the different specimen thickness conditions are Paris-Erdogan model and Walker model. It is also verified that a fatigue crack growth rate exponent of a empirical model may be a material constant at the specimen thickness conditions of 4.75mm and 6.60mm.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.302-305
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• 2007

The springback characteristics of AZ31B magnesium alloy sheet was investigated in OSU draw/bend test. Springback is the elastically-driven change of shape of a part after forming and it should be estimated and controlled to manufacture more precise products in sheet forming. The demands are increasing for magnesium alloy sheet press forming, but the study on its springback characteristics is insufficient. Strip draw/bend tests were conducted with various conditions - die radius, sheet thickness and controlled tensile force. The springback angles were measured from 'sidewall curl' of deformed shape. The tendency of springback angle was observed from the tests.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.113-119
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• 2013

The transient liquid phase (TLP) bonding was used to fabricate autogenous joints in a magnesium alloy AZ31 with the aid of a pure Ni interlayer. A $13{\mu}m$ thick pure Ni foil was used in order to form a Mg-Ni eutectic liquid at the joint interface. The interface of reaction and composition profiles were investigated as a function of bonding time using a pressure of 0.16 MPa and a bonding temperature of $515^{\circ}C$. The quality of the joints produced was examined by metallurgical characterization and the joint microstructure developed across the diffusion bonds was related to changes in mechanical properties as a function of the bonding time.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.1
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• pp.52-58
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• 2004

The material used is a commercial magnesium based alloy AZ31(Mg-3Al-1Zn)sheet with a thickness of 1.0mm. Uniaxial tension tests at warm temperature were carried out to investigate the material characteristics of K, m, and n. A warm drawing process with a local heating and cooling technique was developed to improve formability in this study with results of uniaxial tension tests because it is very difficult for Mg alloy to deform at room temperature by the conventional method. The die and blank holder were heated up, while the punch was water-cooled during deformation. FE simulations considering heat transfer were executed with Mg alloy to investigate the Improvement of deep drawability. For the assessment of improvement those were compare with the results of no considering heat transfer and room temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.707-719
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• 2009

The variables relating to the fatigue behavior have uncertainty and are random. The fatigue crack propagation is, thus, stochastic in nature. In this study, fatigue experiments are performed on the specimen of the magnesium alloy AZ31. The data of the fatigue life are scattered even in the same experimental condition. It is necessary to determine the probability distribution of the fatigue crack propagation life for the reliability analysis as well as the design and maintenance of structural components. Therefore the statistics and the probability distribution for the fatigue crack propagation life are investigated and the best fit probability distribution of that is proposed in this paper.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.221-222
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• 2009

AZ31 마그네슘 합금에 AC 전류를 인가하여 MAO(micro-arc oxidation) process로 양극산화 할 때 알카리 전해액에 첨가되는 sodium silicate(Na2SiO3)의 농도에 따라 형성되는 양극 피막의 구조와 부식특성을 평가하였다. 전해질의 조성은 10g/1 KOH와 4g/1 KF 혼합 전해액에 sodium silicate를 (5, 10, 20, 40, 80)g/1로 달리하여 첨가한 후 $40mA/cm^2$의 전류밀도로 20분간 MAO 처리한 후 양극피막의 조직을 SEM, XRD, EPMA를 이용하여 분석하였고 동전위 분극시험으로 부식 거동을 평가하였으며 micro-vickers 경도계를 이용하여 단면의 경도를 측정하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.193.2-193.2
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• 2016

본 연구에서는 탄산이온이 포함된 수용액에서 규산나트륨의 농도가 AZ31 마그네슘 합금의 플라즈마전해산화 피막형성에 미치는 영향에 대해 알아보았다. 다양한 농도의 규산나트륨 용액에서 DC와 펄스전류를 인가하여 플라즈마전해산화피막을 형성하였으며, 형성된 피막의 surface roughness와 thickness를 분석하였다. 탄산 이온이 포함된 수용액에서 플라즈마전해산화 피막의 형성전압은 규산나트륨의 농도가 높아질수록 높아지는 것으로 나타났다. 하지만 탄산이온이 존재하지 않은 규산나트륨 용액에서의 플라즈마전해산화 피막 형성전압보다 더 낮은 값을 나타내었다. 탄산 이온이 포함된 수용액에서 규산나트륨의 농도가 높아질수록 플라즈마전해산화 피막의 surface roughness와 thickness는 증가하였으며, DC와 펄스전류 모두에서 더 밝은 색상의 균일한 산화피막을 형성할 수 있었다.