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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>
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 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)
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.
Soo‑Bae Kim,Jae‑Gil Jung,Young‑Hee Cho,Su‑Hyeon Kim,Kwangjun Euh,Jung‑Moo Lee 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.7
The effect of ultrasonic melt treatment (UST) on the solidification microstructure of an Al–5Ti–1B alloy containing highvolumefractions of Al3Tiand TiB2particles is investigated for various UST times with different melt holding times. Theas-cast Al–5Ti–1B alloy is composed of TiB2and polygonal Al3Tiparticles (present prior to UST), plate-like Al3Tiparticles,and Al grains (formed during UST and/or solidification). The UST causes a size reduction and homogeneous distributionof the TiB2-agglomerated region containing many submicron-sized TiB2particles pushed to the grain boundaries. The USTslightly decreases the size and improves the distribution of polygonal Al3Tiparticles enriched in the TiB2-agglomeratedregion. Unlike the TiB2and polygonal Al3Tiparticles, which exhibit a minor refining effect, the plate-like Al3Tiparticlesshow a significant refinement with UST application. The UST has a significant effect on the size distribution of Al grains byinducing the formation of medium-sized grains at the expense of small and large grains; however, it only has a slight effecton grain refinement. The degree of microstructure modification increases with increasing UST time but decreases with meltholding time after UST. The mechanisms for the refinement and dispersion of the TiB2and Al3Tiparticles and Al grains arediscussed considering fragmentation, nucleation, and growth behaviors induced by the UST and subsequent solidification.
Saif Haider Kayani,Jae‑Gil Jung,Min‑Seok Kim,Kwangjun Euh 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.7
We investigate the effect of cooling rate on the precipitation behavior during cooling from solution treatment temperatureand post-aging of a high-strength Al–7.65Zn–2.59Mg–1.95Cu–0.11Zr–0.04Ti extruded alloy. Solution treatment at 450 °Ccaused the partial dissolution and disintegration of η phase, along with a partial recrystallization of Al grains. The formationof fine L12-type Al3Zr/Al3(Zr,Ti) (~ 20 nm) and relatively large Ti-rich dispersoids (~ 100 nm) took place during extrusionand/or solution treatment processes. The slow cooling from solution treatment temperature (0.3 °C/min) caused theprecipitation of η phases on coarse Al3(Zr,Ti) particles (formed during solidification), Ti-rich dispersoids (formed duringextrusion/solution treatment), grain boundaries, and grain interiors, thereby resulting in negligible aging responses duringpost-aging at room and elevated temperatures. During fast cooling at 850 °C/min, however, the η phases did not precipitateand thus the Al matrix remained supersaturated, leading to significant aging responses by the formation of GP zones andmetastable η″/η′ precipitates.