• Journal of Korea Foundry Society
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• v.32 no.3
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• pp.150-156
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• 2012

발포금속은 초경량 재료로서 폐기공과 개기공의 두 가지 형태의 구조를 지니고 있으며 폐기공은 내충격성, 흡음성, 단열성의 기능을 지니고 있고, 개기공은 필터, 생체지지대, 촉매재, 열방출재 등으로 사용되고 있다. 개기공발포재는 삼차원 구조모양으로 프리커서를 이용한 압력정밀주조나 기공입자용출법으로 제조하고 있으나 기공의 크기나 셀의 형상, 두께 등을 조절하기에 어려움이 있다. 이를 해결하기 위하여 환경친화적인 펄라이트를 사용하여 목적하는 크기의 그래뉼을 제조한 후, 용융마그네슘합금을 감압주조법으로 주조하여 그래뉼의 크기로 기공율을 조절하고, 주형의 온도와 압력에 따른 유동의 길이를 측정하였다. 그래뉼 직경이 2.3 $mm{\O}$ 일때에 주형의 온도 $300^{\circ}C$ 이상, 압력이 5000 Pa 이상에서 유동길이 6.5 cm 이상을 얻었다.

• Journal of Korea Foundry Society
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• v.36 no.5
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• pp.153-158
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• 2016

The lost foam casting process was used to fabricate Al-Si-Mg cast specimens, and the effects of the chemical composition and process variables on the tensile properties and the mold filling ability were investigated. Some porosity formation was observed in thick sections of the casting and better tensile properties were obtained for thin sections, presumably because of their lower porosity and the higher cooling rate. Tensile properties were not clearly enhanced by grain refining treatment with Ti; however, the elongation was significantly improved by Sr modification of the Al-Si-Mg alloy. The mold filling distance was generally proportional to the pouring temperature of the melt, and the distance was also increased by the addition of Ti.

• Journal of Korea Foundry Society
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• v.37 no.6
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• pp.186-192
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• 2017

The lost foam casting method was used to fabricate Al-Si alloy thin sheet specimens; the effects of chemical composition and process variables on the mold filling and mechanical properties were investigated. The mold filling capability was observed to be proportional to the pouring temperature, and both the vibration imposed during the casting and the application of a pattern coating had rather negative effects. The mold filling capability also decreased with the addition of Mg or TiB. When the Mg content increased, the tensile strength of the cast alloy was enhanced, but the elongation decreased. However, after T6 heat treatment, both the strength and the elongation were improved. TiB addition for grain refining or pattern coating did not significantly affect the tensile properties.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.377-381
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• 2004

Electrical conductivity of Al-Si-Cu-Mg alloy foams of various density produced in powder metallurgical method has been measured using two probe electrical conductivity measurement method. Compressive mechanical properties such as elastic modulus and plastic plateau stress of foams were evaluated from electrical conductivity using power law relation and scaling laws of foam properties. Uni-axial compression test was also performed. Experimentally measured elastic modulus and plastic plateau stress were compared with the values evaluated from electrical conductivity. The computed values were in good agreement with the experimental result.

• Transactions of Materials Processing
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• v.12 no.6
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• pp.588-596
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• 2003

The relationships between evolution of microstructure and mechanical properties of porous Al-3Si-2Mg-2Cu alloy after the foaming and various heat treating were investigated. The foamed alloy having various densities were manufactured by powder compact foaming and heat treated. Then compression test was performed with deformation rate of 0.5/s. The ultimate compression strength was not changed after solution heat treatment but the flow curve after ultimate strength showed very smooth and uniform plateau region. This change of flow curve means that the deformation mechanism is altered from brittle fracture to ductile deformation and the energy absorption property of Al foam is dramatically improved. The improvement of energy absorption without any detriment of mechanical properties is due to that the very brittle precipitation like Al-Cu and Al-Mg was uniformly dissolved in Al matrix after solution heat treatment. And various mechanical properties of Al alloy porous material were improved by 40% with aging of $200^{\circ}C$ and 50min. These improvements are ascribe to the various fine precipitates like $\Omega$ and $\theta$'.

• Proceedings of the Materials Research Society of Korea Conference
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• 2006.11a
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• pp.33.2-33.2
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• 2006

• Journal of Korea Foundry Society
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• v.17 no.3
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• pp.267-275
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• 1997

Fabrication of high strength Mg-Li-Al alloys by squeeze casting was established by the stabilization of melt and mold temperatures, applied pressure and the refining method. The entrapment of inclusions during pouring was prevented using 30 ppi alumina foam filter. The as-cast microstructure consists of a mixture of ${\alpha}$ and ${\beta}$ phases including AILi and $MgLi_2$, Al particles, which are distributed in the ${\beta}$ matrix. The grain sizes of gravity and squeeze casting alloys were 288 ${\mu}m$ and 207 ${\mu}m$ respectively. The addition of Al in Mg-Li alloys promoted the formation of second phase particles, which were adjusted to optimize the properties of Mg-Li-Al alloys. The Mg-10wt%Li-5wt%Al alloy after heat treatment at $350^{\circ}C$ for 1 hour showed the maximum hardness value. This is due to the facts that the amounts of ${\alpha}$ and ${\beta}$ phases and their distributions are dependent upon the solution treatment temperature, and that the amounts of AILi and $MgLi_2Al$ particles are dependent upon the Al content.