• Journal of the Korean institute of surface engineering
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• v.46 no.2
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• pp.80-86
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• 2013

Magnesium alloys of AZ31 containing (0.5, 1, 1.5) wt.% of initially added CaO particles were cast in air, and their oxidation behavior was studied at $450-650^{\circ}C$ in air. The initially added CaO particles either decomposed to dissolve in the ${\alpha}$-Mg matrix or precipitated as $Al_2Ca$ along the grain boundaries of the matrix during casting. The ignition temperatures were $565.4^{\circ}C$ for AZ31, $608.6^{\circ}C$ for AZ31+0.5 wt.%CaO, and $689.7^{\circ}C$ for AZ31+1 wt.%CaO. No ignition occurred for AZ31+1.5 wt.%CaO up to $700^{\circ}C$, displaying good oxidation resistance. The CaO-rich oxide scales that formed on the surface of the AZ31+(0.5, 1, 1.5) wt.%CaO alloys improved the oxidation resistance of AZ31 alloys.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.66-70
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• 2005

Structural components for aerospace, electronics and automobile industry are the main applications for magnesium alloys due to their lightweight and high specific strength. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this paper, the authors aim to improve the formability of AZ31 magnesium alloy. For this, experiment and finite element analysis on used warm deep drawing process with a local heating and cooling technique were done. Both die and blank holder were heated at various warm temperature while the punch was kept at room temperature by cooling water.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.385-388
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• 2005

The use of magnesium alloys meets the need of reducing weight of componests(especially in automotive and aerospace industry) keeping unmodified their mechanical properties. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this study, the authors aim to understand the process condition which can lead to a successful improvement in the formability of a magnesium alloy(AZ31). Experiment and simulations of deep drawing were doned at various warm temperature for the blank and tool(holde and die)while the punch was kept at room temperature by cooling wale. in order to confirm that the deep drawing performance of magnesium alloy can be considerably enhanced with using the local heating and cooling technique.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.6
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• pp.296-302
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• 2020

Magnesium alloys have been rapidly attracting as lightweight structural material in various industry fields because of having high specific strength and low density. It is well known that the crystallographic texture plays an important role in improvement of poor room temperature ductility of magnesium alloys. In this study, high-temperature plane strain compression deformation was conducted on extruded AZ80 magnesium alloy at 723K by varying the strain rates ranging from 5.0×10^-3s^-1 to 5.0×10^-2s^-1 in order to investigate the behaviors of texture formation. It was found that texture formation behaviors in three kinds of specimens were affected by continuous and discontiuous deformation mechanism.

• Corrosion Science and Technology
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• v.8 no.6
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• pp.227-231
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• 2009

Mg and Mg alloys have been used for lots of applications, including automobile industry, aerospace, mobile phone and computer parts owing to low density. However, Mg and Mg alloys have a restricted application because of poor corrosion properties. Thus, improved surface treatments are required to produce protective films that protect the substrate from corrosive environments. Environmental friendly Plasma Electrolytic Oxidation (PEO) has been widely investigated on magnesium alloys. PEO process combines electrochemical oxidation with plasma treatment in the aqueous solution. In this study, AZ91 Mg alloys were treated by PEO process in controlling the current with PC condition and treated time, concentration of NaF, NaOH, and $Na_2SiO_3$. The surface morphology and phase composition were analyzed using SEM, EDS and XRD. The potentiodynamic polarization tests were carried out for the analysis of corrosion properties of specimen. Additionally, salt spray tests were carried out to examine and compare the corrosion properties of the PEO treated Mg alloys.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.3
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• pp.129-134
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• 2020

Due to excellent properties such as high specific strength and low density, application of magnesium alloys have been rapidly increased. However, magnesium alloy has a serious problem that is easily oxidized when exposed to high-temperature. For this reason, magnesium alloys have been generally used for SF6 gas such as protective cover gas in casting and melting, but it has been reported that this gas has a serious influence on global warming. Therefore, many researchers have been studied to improve the oxidation resistance of magnesium alloy. It was reported that addition of Be, Ca and CaO in magnesium alloy can improve the oxidation properties. In this study, the possibility of improving the oxidation resistance by adding CaO extracted from oyster shells was investigated. Oyster shells were completely decomposed into CaO and CO₂ by annealing. With the addition of CaO, a coexistence region of MgO + CaO was formed in the oxide layer and its thickness was also reduced.

• Transactions of Materials Processing
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• v.15 no.3 s.84
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• pp.232-240
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• 2006

Magnesium alloys are expected to be widely used fur the parts of structural and electronic appliances due to their lightweight and EMI shielding characteristics. While the die casting has been mainly used to manufacture the parts from the magnesium alloys, the press forming is considered as an alternative to the die casting for saving the manufacturing cost and improving the structural strength of the magnesium alloy parts. However, the magnesium alloy has low formability at room temperature and therefore, in many cases, forming at elevated temperatures is necessary to obtain the required material flow without failure. In the present study, square cup deep drawing tests using the magnesium alloy AZ31 sheet were experimentally conducted at various elevated temperatures as well as room temperature, and the corresponding finite-element simulations, which calculated the damage evolution based on the Oyane's criterion, were conducted using the stress-strain relations from the tensile tests at various temperatures. The formability predictability by the finite-element analysis was investigated by comparing the predicted damage distributions over the deformed AZ31 sheet at elevated temperatures with the corresponding experimental deformations with failures.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.122-125
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• 2005

Magnesium alloys are expected to be widely used for the parts of structural and electronic applications due to their lightweight and EMI shielding characteristics. While the die casting has been mainly used to manufacture the parts from the magnesium alloys, the press forming is considered as an alternative to the die casting for saving the manufacturing cost and improving the structural strength of the magnesium alloy parts. However, the magnesium alloy has low formability at room temperature and therefore, in many cases, forming at elevated temperatures is necessary to obtain the required material flow without failure. In the present study, square cup deep drawing tests using the magnesium alloy AZ31 sheet were experimentally conducted at various elevated temperatures as well as room temperature, and the corresponding finite-element simulations, which calculated the damage evolution based on the Oyane's criterion, were conducted using the stress-strain relations from the tensile tests at various temperatures. The formability predictability by the finite-element analysis was investigated by comparing the predicted damage distributions over the deformed AZ31 sheet at elevated temperatures with the corresponding experimental deformations with failures.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.94-100
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• 2002

During the last years, great progress has been made in the fields of welding power sources and filler materials for the MIG-welding of magnesium alloys. This advice resulted in a better welding process, md, therefore, in highly improved welding results. Furthermore the gap between short-circuiting- and spray-arc-trunsfer could be closed by the triggered short-circuiting- and the short-circuiting-arc with pulse overlay. A crucial contribution to the welding process is the energy input into the filler material. Many problems result from the physical properties of magnesium, for instance its narrow interval between melting point 600$^{\circ}C$ and vaporization point 1100$^{\circ}C$. The energy input into the filler material has to be regulated in such a way that the wire will melt but not vaporize. For th is reason, special characteristics of power sources hue been examined and optimized with the help of high-speed-photographs of the welding process with particular consideration of the drop detachment. An important improvement of the weld seam profile has been achieved by using filler material of only 1.2 mm in diameter. The experiments hue been made with 2.5 mm thick extruded profiles of AZ31 and AZ6l. The results of tensile testing showed strength values of 80 to 100% of the base metal. B ending angles up to 60$^{\circ}$ have been reached. The fatigue strength under reversed bending of the examined magnesium alloys after welding reaches 50% of the strength of the base metal. When the seam reinforcement is ground of the fatigue strength can be raised up to 75% of the base metal.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.522-528
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• 2012

It is the aim of this paper to propose the empirical fatigue crack propagation model fit to describe a crack growth behavior of AZ31 magnesium alloys. The statistical data of a crack growth for an estimation are obtained by fatigue crack propagation tests under the three cases of maximum load. The empirical models estimated are Paris-Erdogan model, Walker model, Forman model, and modified-Forman model. It is found that the empirical model fit to describe a crack growth behavior of AZ31 magnesium alloys is Paris-Erdogan model and Walker model. It is also verified that a fatigue crack growth rate exponent of a empirical model is to be a material constant.