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Euh, Kwangjun,Kang, Suk Bong Elsevier 2005 Materials science & engineering. properties, micro Vol.395 No.1
<P><B>Abstract</B></P><P>Aluminum (Al) matrix composites reinforced by SiC particulates (SiCp/Al) were fabricated by the atmospheric plasma spraying. The composite powder, as a feedstock for plasma spraying, was prepared by ball milling of pure Al powders with 55 vol.% SiC particles. The feedstock was deposited into a freestanding bulk composite sheet on a graphite substrate by atmospheric plasma spraying. As-sprayed composites had a great amount of porosity, which deteriorates the thermo-physical properties, especially the thermal conductivity. In order to reduce the porosity of the plasma-sprayed SiCp/Al composite sheets, rolling processes were carried out at the room and elevated temperature with the thickness reduction of about 20%. The thermal conductivities of the rolled composites were considerably enhanced with the decrease of the porosity in the composites, while the coefficients of thermal expansion (CTEs) of the composites were slightly affected by the rolling process.</P>
대기 플라즈마 용사법으로 제조된 SiCp/Al 복합재료의 열전도도 특성
어광준,강석봉,Gui, Manchang 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.1
Feedstock for plasma spraying was prepared by ball milling with A1-55 vol.%SiC and Al-75 vol.%SiC powder mixtures in different conditions. The average size of SiC particles was varied from 8 to 30 gm. Freestanding SiC_(p)/Al composites were fabricated by atmospheric plasma spraying onto a graphite substrate. Thermal conductivity of the plasma-sprayed composites was measured at room temperature of 25℃ by the laser flash method. Thermal conductivity of the sprayed composites was significantly lower than that of conventionally cast SiCp/Al composites. Thermal conductivity was varied considerably with respect to the SiC size and feedstock preparation method. The deterioration mechanism of thermal conductivity in the sprayed composites was elucidated, and numerical analyses based on theories of Maxwell and thermal boundary resistance were carried out. (Received September 30, 2004)
플라즈마 spray forming법으로 제조된 Al-SiCp 복합재료의 후속공정에 의한 물성 향상
어광준,강석봉 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.3
In order to fabricate aluminum matrix composites reinforced by SiC particulates, atmospheric plasma spray forming method was adopted. Aluminum and SiC powders were mechanically mixed for plasma spraying feedstock. The feedstock was deposited into freestanding bulk composite on a graphite substrate. As-sprayed composites had a great amount of porosity, which reduced thermal properties, especially in thermal conductivity. The spray-formed Al-SiCp composites were rolled at the room and elevated temperature and hot isostatic pressed (HIPped) at 500℃ under 100 MPa. By rolling, the amount of porosity decreased and consequently thermal conductivity increased. Although, the amount of porosity hardly decreased by HIP, thermal conductivity increased due to the precipitation of solid solution elements such as Fe and Si. Coefficients of thermal expansion (CTEs) of the composites were affected less significantly by post treatment.
대기 플라즈마 용사에 의한 Al-SiC 복합재료 판재의 제조에 미치는 공정변수의 영향
어광준,강석봉,양병모 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.6
Increased electronic packaging density requires thermal management materials with high thermal conductivities and low coefficients of thermal expansion (CTEs) matching those of ceramic substrates or semiconductors. Recently, metal matrix composites (MMCs) have been developed, which provide unique combination of properties that make them candidates for thermal management materials. Most of conventional processes to fabricate MMCs have complicated steps that reduce the cost effectiveness, such as the infiltration process requiring a preform preparation and long process time. Plasma spraying can be adopted to produce MMCs in a flexible and cost effective manner. In this study, SiC particles reinforced Al matrix composites were fabricated by atmospheric plasma spraying method. Al and SiC powders were blended and sprayed with plasma arc power. SiC were uniformly dispersed in the Al matrix with a volume fraction of up to 46%. There were also pores in the composite with a range of 1.8∼12 vol.%, which could be tailored by process parameters. The experimental CTEs showed 13.5∼17.6×10^-6/℃ for the Al-SiC composite containing about 40 vol.% SiC, which were matched well with the predicted ones.
가스-용탕 in-situ 반응에 의한 AIN/Al 복합재료의 제조
김재덕,어광준,이정무,강석봉 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.5
Fabrication method of aluminum nitride reinforced aluminum composites using gas-melt in-situ reaction was investigated. AA 5083 aluminum alloy was melted in vacuum and nitrogen atmosphere, and then nitrogen gas bearing 12.5% ammonia gas was injected in the molten alloy through alumina and graphite tube for 4 hours at the temperature of 1100℃. The melt was divided into the upper and lower parts. There were many AlN particles in the upper part and no AlN in the lower part. In order to mix the upper and lower part, an impeller was introduced to the melt. There was also two parts with decreased thickness of the upper part and small amount of AlN in the lower part. Formation of AlN has been identified by optical and transmission electron microscopy, X-ray diffraction, and electrolytic extraction method. AlN was evolved in the form of a cluster with hexagonal particles of 1 μm and a rod of about 3 μm length.
가스/용탕의 in-situ반응에 의한 Al-Mg/AIN 복합재료 제조
김재덕,어광준,이정무,강석봉 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.8
Effects of fabrication condition on the formation of A1N by means of gas/melt in-situ reactions were investigated through injection of mixture gas of 95% N₂+5%H₂into the commercial grade A5083 alloys. In this investigation, the fabrication was performed in the temperature range of 1000 to 1200℃ for up to 4 hours. The fabricated composites were characterized using X-ray diffraction, scanning electron microscopy with dispersive X-ray microanalysis and transmission electron microscopy. The volume fraction of MN formed in the specimens increased with increasing reaction time and reaction temperature as well, while the trend of increment of volume fraction of AIN per hour is different with the reaction temperature. The formation of A1N by means of gas/melt in-situ reactions was examined through the thermodynamic and kinetic considerations.
Ahn, Tae-Young,Jung, Jae-Gil,Baek, Eun-Ji,Hwang, Seong Sik,Euh, Kwangjun ELSEVIER SCIENCE 2017 Journal of Alloys and Compounds Vol.701 No.-
<P><B>Abstract</B></P> <P>The precipitation behavior of the multicomponent Al–6Mg–9Si–10Cu–10Zn–3Ni (wt%) alloy was investigated during artificial aging at 120 °C through complementary experimental methods including hardness and electrical resistivity measurements, compression testing, differential scanning calorimetry, and transmission electron microscopy. The solution treatment causes the dissolution of the preexisting θ-Al<SUB>2</SUB>Cu and hcp Zn phases, thereby increasing the concentrations of Zn and Cu species in the Al matrix. During aging, two resistivity peaks (I<SUB>R</SUB>, II<SUB>R</SUB>) become visible followed by the appearance of the related hardness peaks (I<SUB>H</SUB>, II<SUB>H</SUB>). Spherical Guinier-Preston (GP) zones are formed first and then subsequently transformed into ellipsoidal GP zones. The former process results in the appearance of the I<SUB>R</SUB> peak, while the latter process produces the I<SUB>H</SUB> peak. During transformation of the ellipsoidal GP zones to hcp Zn, GPI zones are additionally formed, leading to the appearance of II<SUB>R</SUB>. The following transformation of the GPI zones into the θ''-Al<SUB>3</SUB>Cu phase leads to the appearance of the II<SUB>H</SUB> peak. Both the ellipsoidal GP zones and hcp Zn phases contain large quantities of Cu atoms, while the θ''-Al<SUB>3</SUB>Cu phase does not have any Zn atoms. Based on these insights into the structural and chemical compositional evolution of complex precipitates, the strengthening mechanism of the multicomponent alloy during aging has been established.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Structural and chemical evolution of clusters and precipitates are clarified. </LI> <LI> During aging, two resistivity peaks are followed by their related hardness peaks. </LI> <LI> Zn and Cu clusters are detected via the first and second resistivity peaks. </LI> <LI> Zn cluster and hcp Zn contain Cu atoms, but θ'' phase does not have any Zn atoms. </LI> <LI> Maximum alloy hardness is achieved when both the θ'' phase and hcp Zn are formed. </LI> </UL> </P>
Ju‑Hye Kim,Jae‑Gil Jung,Eun‑Ji Baek,최윤석,Kwangjun Euh 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2
We investigated the microstructures and mechanical properties of multiphase-reinforced in situ aluminum matrix composites(AMCs) prepared with various combinations and contents of Li, Mg, Si, Cu, Zn, Sn, and Ni. The area fractions of thesecondary phases in the as-cast AMCs ranged from 26% to 58%, and the types of secondary phases depended on the alloychemical compositions. The type and amount of secondary phases were more important than matrix strengthening in determiningthe alloy mechanical properties. Composite hardness and compressive stress increased while fracture strain decreasedwith increasing total area fraction of the secondary phases up to 40%. The formation of coarse primary and soft/heavySn-containing phases significantly deteriorated the alloy mechanical properties. Annealing also influenced the mechanicalproperties of the AMCs by changing the microstructures of the secondary phases and Al matrices.