• 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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• 2014.11a
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• pp.44-44
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• 2014

Magnesium alloy AZ31 sheet를 자동차용 부품으로 사용하기 위해서는 내식성, 전착도장성등의 신뢰성을 확보해야 한다. 이를 위해서 우리는 Phosphate, manganese, silicon계열의 화성처리제를 이용하여 자동차 부품으로 사용가능한 신뢰성확보를 위해 표면처리 방법에 관한 연구를 진행 하였다.

• 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.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.33-33
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• 2015

마그네슘 합금은 자동차, 항공기, 기계 및 휴대용 전기전자 부품 등에 적용을 위해 많은 연구들이 진행되어 왔다. 현재 마그네슘 합금의 실용화에 있어서 가장 큰 걸림돌 중 하나는 불충분한 내식성이다. 마그네슘 합금의 내식성은 표면의 자연적으로 형성되는 피막의 보호성 및 2상 입자들의 존재에 의한 갈바닉 부식에 의해 영향을 받는다. 본 논문에서는 AZ31 마그네슘 합금의 내부에 포함되어 있는 캐소딕 불순물 입자들과 자연산화피막 그리고 화학적 또는 전기화학적으로 형성된 산화피막들이 합금의 내식성에 미치는 영향에 대해서 연구하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.9-10
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• 2011

• Transactions of Materials Processing
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• v.21 no.7
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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.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.473-480
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• 2008

Sheet metal forming of Mg alloy is usually performed at elevated temperature because of the low formability at room temperature. Therefore, strain rates affected with the forming temperature and speed must be considered as important factor about formability. Effects of process parameters such as various temperatures and forming speeds were investigated in circular cup deep drawing. From the experimental results, it is known that LDR (Limit Drawing Ratio) increase as the strain rate increase. On the contrary, the FLD (Forming Limit Diagram) shows lower value as faster strain rate. Therefore, anisotropy values are investigated according to the temperature and strain rates at each forming temperature. R-values also represent higher value as faster strain rate. It is known that the formability can be different with the deformation mode on warm forming of AZ31 alloy sheet.

• Transactions of Materials Processing
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• v.17 no.7
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• pp.466-472
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• 2008

In this paper, tension tests and formability tests are performed to construct a database related to mechanical properties and the formability of the AZ31B Mg alloy sheet. A forming test with a hemi-spherical punch is conducted at varying temperatures to establish a forming limit diagram. In order to verify the applicability of the analysis using the conventional flow hardening model, a finite element analysis is performed on the hemi-spherical punch forming process and the results are compared with experimental ones. The study investigates problems involving a computational analysis that does not consider flow softening of the magnesium alloy at elevated temperatures.

• Transactions of Materials Processing
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• v.15 no.7 s.88
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• pp.504-511
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• 2006

The drawability of AZ31B magnesium sheet is estimated at various temperatures($200,\;250,\;300,\;350\;and\;400^{\circ}C$), and forming speed(20, 50, 100mm/min), thickness(0.5, 0.8, 1.0, 1.4mm). The deep drawing process of circular cup and square cup were used in forming experiments. Experimental and FEM analysis are performed to investigate drawability and affection of controlled blank holding force. Through the controlled blank holding force, drawability was improved. Limit drawing ratio is increased from 2.1 to 3.0 in circular cup drawing and change of thickness is decreased from 16.3 to 6.9%. This result is verified by FEM analysis. Through the observation of microstructure, the main cause is investigated as a quantity of the dynamic recrystallization.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.48-52
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• 2006

The drawability of AZ31B magnesium sheet is estimated at various temperatures (200, 250, 300, 350 and $400^{\circ}C$), and forming speed (20, 50, 100 mm/min), thickness (0.5, 0.8, 1.0, 1.4 mm). The deep drawing process of circular cup and square cup were used in forming experiments. Experimental and FEM analysis are performed to investigate drawability and affection of controlled blank holding force. Through the controlled blank holding force, drawability was improved. This result is verified by FEM analysis. Through the observation of microstructure, the main cause is investigated as a quantity of the dynamic recrystallization.