• Transactions of Materials Processing
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• v.15 no.2 s.83
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• pp.148-152
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• 2006

In this study, the experiments of warm deep drawing were done with heated die, and with heated die, and blankholder, and cooled punch in order to investigate the formability of AZ31 magnesium alloy sheet in warm deep drawing. For this, warm deep drawing experiments were executed under various temperatures and punch velocities. The results of warm deep drawing with heated die showed that fracture occurred around the punch part at punch velocity of 75mm/min and punch stroke of 10mm under temperature range of 373-523K, but did not occur under temperature range of 548-673K even punch stroke of 25mm. And fracture at the punch stroke of 25mm and the temperature of 523K did not occur under the punch velocity of 30mm/min, but occurred under punch velocity of 75 and 125mm/min. Also warm deep drawing with heated die and blankholder, and cooled punch showed that the temperature range happening maximum height under punch velocity of 10-100mm/min was around 498-523K. Finally, with heating and cooling technique necking of AZ31 magnesium alloy occurred at punch shoulder part under the temperature range of 293-423K, but at die wall part under the temperature range of 473-573K.

• Design & Manufacturing
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• v.10 no.1
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• pp.12-18
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• 2016

Although magnesium alloy has received much attention to date for its lightweight and high specific strength, their applications are impeded by the low formability which is caused by the hexagonal crystal structure at room temperature. In general, equal-channel angular extrusion(ECAE) is recognized as one of the attractive severe plastic deformation techniques where the processed bulk metals generally achieve ultrafine-grained microstructure leading to improved physical characteristics and mechanical properties. ECAE process has several parameters such as angle of die, process temperature, process route and speed. During ECAE process of Mg alloy, these parameters has great influence on the extrudability and the mechanical properties of alloy. The aim of this study is to estimate the influences of process conditions on the formability of AZ31 and AZ31-CaO alloys. Mg alloys are processed through ECAE at elevated temperatures using three types of die with channel angle of $90^{\circ}$, $110^{\circ}$, $135^{\circ}$ using route $B_c$, respectively. This study discusses the feasibility of using ECAE to improve both formability and strength on magnesium alloys by comparative analyzing the mechanical properties and microstructural evolution in each condition.

• Journal of Korea Foundry Society
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• v.30 no.6
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• pp.217-223
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• 2010

Foamed metal has become an attractive material, which has unique physical, thermal, acoustic, damping and mechanical properties, because large amount of pores are distributed in the metal matrix. Therefore, metal foam can be used for the light weight application in automotive, locomotive, aerospace fields. Aluminum foams have been developed successfully and will be employed in the next generation of energy absorption boxes. Magnesium alloys are most eligible candidate to substitute aluminum alloy, especially for lower density and higher damping properties in wide industrial fields. Magnesium alloy foams are expected to be particularly advantageous due to two thirds the density of aluminum. However, foaming magnesium have been weakness of high activity, difficult processing and very dangerous. In order to upgrade this problem, AM50 magnesium alloy which has better characteristic is safe to use through foaming time and alloying element in this study.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.6
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• pp.93-98
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• 2005

The purpose of this study is to confirm the improvement of formability of AZ31 magnesium alloy sheet by using local heating and cooling technique. For this, the experiments of warm deep drawing were done under the temperatures of $100^{\circ}C\~400^{\circ}C$, and the punch velocity of 10, 100mm/min. Also FE analysis under the temperatures of blankholder and die of $150^{\circ}C,\;225^{\circ}C\;and\;300^{\circ}C$ for tools(holder and die) was executed with considering heat teansfer. From the results, the formability of AZ31 magnesium alloy, espicially the temperatures of $225^{\circ}C\~250^{\circ}C$ for tools(holder and die)improved remarkably. And the experiments and simulations showed that necking under room temperature for tools occured under the part of punch shoulder while at $300^{\circ}C$ for tools, at the part of die shoulder.

• Journal of the Korean institute of surface engineering
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• v.43 no.2
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• pp.73-79
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• 2010

A chromium-free conversion coating for AZ31 magnesium alloy has been obtained by using a permanganatephosphate solution, which has been developed with acid pickling. Examination have been carried out on the conversion coatings for morphology, composition and corrosion resistance. The morphology of the conversion-coated layer was observed using optical microscope and SEM. It was shown that the conversion coatings are relatively uniform and continuous, with thickness 1.8 to 2.7 ${\mu}m$. The chemical composition of conversion coating was mainly consisted of Mg, O, P, K, Al and Mn by EDS analysis. It was found that the corrosion resistance of the AZ31 magnesium alloy has been improved by the permanganate-phosphate conversion treatment from electrochemical polarization.

• 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.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.686-691
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• 2011

To develop creep resistant die-cast Mg alloys, various alloying elements, including Ca, Ce, and Sr, were added to a Mg-Al alloy. The AXE710 alloy was produced on a 320 ton high-pressure die casting machine. The microstructure and creep properties of the alloy were examined. The creep behavior was investigated at $150^{\circ}C$ for stresses ranging from 50 to 100 MPa. The stress exponent was derived from the relationship between normalized secondary creep rates and compensated effective stresses. It was found to be 4.9, indicating that the dislocation climb is a dominant creep mechanism.

• Journal of Korea Foundry Society
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• v.35 no.2
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• pp.36-43
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• 2015

In this study, the influences of aluminum and tin additions (individual and combined) on corrosion behavior of magnesium alloy have been determined. The studied alloys were fabricated by permanent mold casting method to measure the corrosion properties, a potentiodynamic test, hydrogen evolution test and immersion test were carried out in a 3.5% NaCl solution at pH 7.2. From the results of microstructure analysis, the Mg-9Al-1Zn alloy was found to be composed of ${\alpha}$-Mg and rod-like $Mg_{17}Al_{12}$ phase and the Mg-5Sn-5Al-1Zn alloy was found to be composed of ${\alpha}$-Mg, rod-like $Mg_{17}Al_{12}$ and $Mg_2Sn$ phases. In the case of the Mg-9Sn-1Zn alloy, the microstructure was composed of ${\alpha}$-Mg and eutectic $Mg_2Sn$ phase. With Sn addition (individual and combined), the corrosion resistance of the Mg alloys improved.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.3
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• pp.45-53
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• 2009

Die casting process of Mg alloys for high temperature applications was studied to produce an engine oil pan. The aim of this paper is to evaluate die casting processes of the Aluminium oil pan and in parallel to apply new Mg alloy for die casting the oil pan. Temperature distributions of the die and flow pattern of the alloys in cavity were simulated to diecast a new Mg alloy by the flow simulation software. Dies have to be modified according to material characteristics because melting temperature and heat capacity are different. We changed the shape and position of runner, gate, vent hole and overflow by the simulation results. After several trial and error, oil pans of AE44 and MRI153M Mg alloys are produced successfully without defect. Sleeve filling ratio, cavity filling time and shot speed of die casting machine are important parameter to minimize the defect for die casting Magnesium alloy.

• Journal of Korea Foundry Society
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• v.31 no.4
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• pp.212-217
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• 2011

The effects of alloying element and grain refinement on the tensile properties of magnesium alloy poured into sand mold were investigated. The strength of magnesium alloy was greatly increased by the addition of aluminium and that was increased with the increased aluminum content added up to 8.10 wt% and decreased beyond that. Even though the strength of Mg-8.10 wt%Al alloy was rather decreased by the addition of zinc, that was increased with increased zinc content added up to 0.50 wt% and decreased with the increased one beyond that. The maximum tensile strength was obtained with 0.50 wt%Mn added. The strength and elongation were simultaneously increased with grain refinement and the optimum amount of strontium addition for this was 0.30 wt%. The optimum chemical composition was obtained and the yield strength, tensile strength and elongation of the alloy with this composition were 90.2, 176.3MPa and 4.43%, respectively.