• Journal of Korea Foundry Society
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• v.14 no.5
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• pp.383-392
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• 1994

• Journal of Korea Foundry Society
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• v.28 no.1
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• pp.5-14
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• 2008

• Journal of Korea Foundry Society
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• v.13 no.1
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• pp.17-24
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• 1993

• Journal of Korea Foundry Society
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• v.28 no.2
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• pp.45-51
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• 2008

• Journal of Korea Foundry Society
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• v.20 no.4
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• pp.217-223
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• 2000

• Journal of Korea Foundry Society
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• v.13 no.2
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• pp.124-130
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• 1993

• Journal of Korea Foundry Society
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• v.14 no.1
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• pp.62-74
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• 1994

The concentration and particle size distribution of non-metallic inclusions which suspended in the molten aluminum at $700^{\circ}C$ were measured by using LiMCA apparatus. The result revealed that the number of inclusions increased with increasing the applied current or decreasing the orifice diameter, while decreased with increasing the purity of aluminum. And also, it was found that the number of inclusions increased with increasing the amount of boron added to molten aluminum. This was found to be attributed to the formation of the inclusions of TiB and $V_3B_2$. It was investigated that the average concentration of inclusions in a constant volume of 20ml of molten aluminum was increased in the order of pure molten aluminum, molten aluminum containing 20ppm of boron and molten aluminum used repeatly in the experimental casting in this study.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.161-170
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• 2002

The Purpose of this study was to investigate the chemically improvement of metal-ceramics bond strength in the course of recasting Ni-Cr metal composite system with 10wt.%, 20wt.% and 30wt.% aluminum respectively. We have tested the bond strength, micro-structure, chemical composition of each metal composites and metal- ceramic bond interfaces by 3-point bending strength tester, SEM and EDS. We have made the conclusions through this study as follow: 1. The most suitable amount of aluminum to the Ni-Cr metal composite recasting is 20wt. % for improving metal-ceramics bond strength with debonding strength value of 49.54 kgf/mm2. 2. The aluminum must be changed to small spread alumina like phases and second aluminum-metal composites phases in the morphology of Ni-Cr metal composite system by adding during it's casting. These second phases have inclined functional oxide phases mixed with metal elements and they must take roll to improvement of metal-ceramics bond strength. 3. In the case of 30wt.% aluminum appended to Ni-Cr metal composite system, an excess of second inclined functional oxide phases produce cracks and spalling of them apart from it's base material. It must be a important factor of reduction of metal-ceramics bond strength.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.85-96
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• 2020

The effect of an aluminum scrap addition ratio on the tensile and solidification cracking properties of the AC4A aluminum alloy in the as-cast state and heat-treated state were investigated in this study. Generally, the expected problem of using scrap in aluminum casting is an increase of hydrogen and Fe element inside the aluminum melt. Another issue is an oxide film which has a weak interface with the molten aluminum and acts as potent nucleation sites for internal porosity and crack initiation. Solidification cracking is one of the critical defects that must be resolved to produce high quality castings. A conventional evaluation method for solidification cracking is a relative and qualitative analysis method which does not provide quantitative data on the thermal stress in the solidification process. Therefore, a newly designed solidification cracking test apparatus was used in this study, and the device can provide quantitative data. As a result, after conducting experiments with different scrap addition ratios (0%, 20%, 35%, 50%), the tensile strengths and elongations in the as-cast state were 214, 187.7, 182.1 and 170.4MPa and 4.6%, 3.4%, 3.1% and 2.3%, respectively. In the case of the T6 heat-treated state, the tensile strengths and elongations were 314.9, 294.6, 293.1 and 271.1MPa and 5.4%, 4.6%, 3.8% and 3.1%, respectively. The strength of the solidification cracking was 3.1, 2.4, 2.2and 1.6MPa as the scrap addition ratio increases.

• Resources Recycling
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• v.11 no.6
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• pp.31-37
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• 2002

Microstructure of aluminum alloys produced by the different mixing ratio of secondary ingot made by aluminum UBC (used beverage can) and virgin aluminum was investigated. The phase transitions of casted ingot by heat treatment were also studied. The alloys were melted at the electric resistance furnace, then casted using ceramic filter. Homogenization heat treatment was conducted at $615^{\circ}C$ for 10hrs to control cast microstructure. There were several kinds of phases, in as-cast condition, such as $\alpha$($Al_{12}$ $((Fe,Mn)_3$Si), $\beta$($Al_{6}$ (Fe,Mn)), and fine $Mg_2$Si phases. Especially, the amount of $\beta$-phase which was harmful in forming process was large. The $\beta$-Phase formed was transformed to u-phase by heat treatment. The fine $Mg_2$Si in the aluminum matix was also transformed to $\alpha$-phase by this heat treatment. Impurities filtered during casting process were identified as intermetallic compounds of Fe, Cu, Si.