• Korean Journal of Materials Research
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• v.13 no.9
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• pp.619-624
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• 2003

This paper describes a method to control Mn and Fe contents in recycled AZ91D ingots, based on the mutual solubility of Mn and Fe in AZ91 alloy melts. For this purpose, Fe solubility with the change of Mn content and temperature was investigated in the homogenized and re-precipitated liquid AZ91 alloy. The increase of the amount of Mn added to the melt resulted in the decrease of Fe content. The data obtained in this study was adopted to the pilot plant for recycling of the scrap. As a result, Mn and Fe contents measured in the recycled ingot were in good agreement with ASTM B93 standard.

• Korean Journal of Materials Research
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• v.9 no.7
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• pp.715-723
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• 1999

Magnesium has been used as wheel materials in the automotive industry for more than 20 years. The magnesium wheels, which are lighter by 25% than aluminum wheels, provide easy controllability providing excellent road holding by the reduction of weight. The purpose of this work is to develop cast AZ91D alloy wheel by sand cast and permanent mold cast. The fluxless melting with the protective gas $(SF_6+CO_2)$ was Performed to eliminate oxidation of melt and impurity. The transfer of molten magnesium to the mold was done by using gas-pressurized Pump system through the heated pipe. The mechanical properites of AZ91D alloy wheel were investigated as a function of heat treatment, ingot composition.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.516-521
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• 2002

A study was carried out to grow an understanding of the microstructural development of friction stir welds on an AZ91D magnesium alloy, and to evaluate the mechanical properties of the welds. AZ91D plates with the thickness of 4mm were used, and the microstructural development of the weld zone was investigated using optical and scanning electron microscopes. Square butt welding joint with good quality was obtained at the conditions of under 187mm/min of travel speed with 1100 to 1250 rpm of tool rotation speed. The microstructure within the weld region consisted of fine equiaxed grains with no evidence of the original dendritic structure. The hardness tests showed slightly increased harness in the weld region, and the minimum hardness measured is in that of the parent material. Tensile strength of the weld zone was remarkably improved due to very fine recrystallized structure. XRD pattern of weld zone revealed the removal of $\beta$ intermetallic compounds, $Mg_{17}$Al$_{12}$, which had been distributed in the base metal.l.

• Journal of Korea Foundry Society
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• v.15 no.2
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• pp.184-193
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• 1995

Effects of process parameters during thixocasting, such as solid volume fraction, mold temperature and extrusion ratio, on the mold filling behaviour and fluidity of Mg alloy(AZ91D) have been investigated. The semi-solid ingot held for 60 minutes at the semi-solid temperature range did not contain the equilibrium volume fraction of solid as expected from the phase diagram. Therefore, in order to obtain the desired solid fractions, and to suppress the exaggerated grain growth during heating, it was required to heat the ingot rapidly up to the temperature $10^{\circ}C$ higher than the semi-solid temperature suggested from the phase diagram for a specific volume fraction of solid. The experimental results show that mold filling behaviour and fluidity can be improved with the use of the higher mold temperature and the lower volume fraction of solid, but remain nearly unaffected by the change of extrusion ratio.

• Journal of Korea Foundry Society
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• v.34 no.6
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• pp.200-213
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• 2014

Pure magnesium and magnesium alloys have been applied to various kinds of industrial fields, especially automotive and electronic parts. These parts are manufactured mainly through a diecasting process. These days, magnesium ingots are used as raw material, and recycled ingots are often used for commercial purposes. But the quality of virgin magnesium and recycled ingots is not secure. Therefore, massive casting defects can occur, and some things manufactured can be damaged by these defects. This study evaluated the inclusions of virgin magnesium and recycled ingot. It also included composition analysis by spectrometer, measuring inclusion contents by SEM & EDS, and performing a brightness test on fractured surfaces. The brightness test is generally very easy and obtains results quickly, so its results have been compared with the results obtained from various test methods. From the test results, we obtained a satisfactory result in evaluating inclusion and oxide. The brightness values are lower as the inclusion contents are higher. When the brightness value is over 47 in AM50A and 44 in AZ91D, the mechanical properties are expected to be good.