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- 저자 : 최창옥 ( Hyo Gyoung Kang (검색결과 4 건)
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AC4C 합금의 기계적 성질에 미치는 주조조건과 열처리의 영향에 관한 연구
강효경,천병욱,최창옥 ( Hyo Gyoung Kang,Byung Wook Cheon,Chang Ock Choi ) 한국주조공학회 1993 한국주조공학회지 Vol.13 No.5
N/A AC4C alloy casts in the metallic mold, zircon sand mold, silica sand mold and shell mold with the pouring temperatures of 680, 710 and 740℃ have been investigated. The tensile strength, elongation and hardness of AC4C alloy castings have been influenced by the kind of molds used. The mechanical properties in zircon sand mold castings were greater than those in other sand mold castings, but were inferior to the properties in metallic mold castings. Eutectic Si particle size and DAS were increased in the order of metallic mold, ziron sand mold, silica sand mold and shell mold. Also, they were increased with the increase of pouring temperatures. DAS, eutectic Si particle size and grain size decreased with the increase of mechanical properties as the cooling rate increased. The eutectic Si particle size and DAS of AC4C alloy castings after T6 treatment were decreased in as-cast. The variation of eutectic Si particle size has been effected on the tensile strength, elongation and fractured surface.
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Influence of Microstructures on Mechanical Properties of Al-Si-Cu-Mg Cast Alloys
Kang, Hyo Gyoung,Choi, Chang Ock,Ogi, Keisaku 동아대학교 생산기술연구소 2000 生産技術硏究所硏究論文集 Vol.5 No.1
A commercial Al-Si-Cu base alloy (JIS AC4B) and the similar compositions of pure alloys with 0 to 0.7%Fe were solidified at the cooling rate of 2.7 to 14.4K/s. Tensile tests and quantitative microstructure analysis were performed on the as cast specimens and T_6specimens. Tensile strength (бB) increased as the microstructure became finer. бB rose linearly with decreasing of secondary dendrite arm spacing(DAS) of primary α , while the modification of eutectic Si with Sr had a smaller effect. The crack propagated along dendrite arms and the fracture surface exhibited a structure whose coarseness was close to DAS. Fe-rich intermetallic compounds took the acicular and chinese script type shapes. Higher cooling rate and more Sr addition promoted the crystallization of chinese type one. The Fe-rich compounds decreased the elongation, though they tended to raise the yield strength. TEM analysis revealed that the aging process was influenced by eutectic Si and minor elements, however the these phenomena may have little influence on tensile properties.
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Kang, Hyo-Gyoung,Choi, Chang-Ock,Ogi, Keisaku 동아대학교 환경문제연구소 1999 硏究報告 Vol.22 No.2
TEM analysis was applied to the investigation on age hardening processes of a commercial JIS ACAB alloy and the similar compositions of pure N-Si-Cu and Al-Si-Cu-Mg cast alloys. A series of alloy specimens were solution treated at 773K for l0hr and subsequently aged at 433K and 473K for l0min to 10⁴min. The typical hardness-aging time relations are obtained on each alloy specimen. The maximum hardness of specimen aged at 433K becomes larger from Hv95 to Hv152 as the Mg content of alloy increases from 0 to 0.43mass%. TEM reveals many dislocations around eutectic Si particles, which should be introduced into aphase during quenching from solution treatment emperature, because of the difference in the thermal expansion coefficient between α-natrix and eutectic Si. The formation of GP Zone is suppressed and the precipitation of θ' is promoted in the ternary 4-Si-Cu alloy, which contains higher density of dislocations. Many tiny particles of Mn-rich compound precipitate in the α matrix of solution-treated. AC4B alloy, which decrease the Cu content of a phase and the age-hardening ability of the alloy.
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Kang, Hyo-Gyoung,Choi, Chang-Ock,Ogi, Keisaku 동아대학교 환경문제연구소 1999 硏究報告 Vol.22 No.2
The effects of cooling rate and additions of Sr and Ti-B on microstructural features such as grain size, dendrite arm spacing, morphologies of eutectic silicon and iron rich compound were investigated for the Al-6.55%Si-2.78% Cu-0.59%Fe-0.38%Mg-0.34%Mn alloy of ACAB type. This alloy solidified in the order of primary α, a+a-AlFeMnSi compound eutectic, α+Sieutectic, α+β-AlFeMnSi. a +Si+Mg₂Si and α+Si+Al₂Cu eutectic. The grain size, dendrite arm spacing, the size of eutectic silicon particles and the length of needle like β-AlFeMnSi decreased with increasing the cooling rate, and they were in linear relations on logarithmic scales. Addition of small amount of Ti-B remarkably refined grain size while it practically unaffected the other solidification structures At the cooling rate of 2.73K/s, 14.38K/s and 108.08K/s, the eutectic silicon crystals fully modified by adding Sr more than 60ppm, 20ppm and 5ppm, respectively. Addition of Sr and higher cooling rate tended to modify the needle like iron rich compounds to Chinese script type one. DSC analysis revealed that the Sr modification was accompanied by the characteristic changes in cooling curve.
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