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수렴성빔 전자회절법을 이용한 리오캐스팅시킨 과공정 Al-Si합금에서 실리콘초정의 격자상수 측정
이정일,김긍호,이호인,Lee, Jung-Ill,Kim, Gyeung-Ho,Lee, Ho-In 한국현미경학회 1995 Applied microscopy Vol.25 No.3
The morphological changes of primary solid particles as a function of process time on hypereutectic Al-15.5wt%Si alloy during semi-solid state processing with a shear rate of $200s^{-1}$ are studied. In this alloy, it was observed that primary Si crystals are fragmented at the early stage of stirring and morphologies of primary Si crystals change from faceted to spherical during isothermal shearing for 60 minutes. To understand the role of Al dissolved in the primary Si crystal by shear stress at high temperature, lattice parameters of the primary Si crystals are determined as a variation of high order Laue zone(HOLZ) line positions measured from convergent beam electron diffraction(CBED) pattern. The lattice parameter of the primary Si crystal in the rheocast Al-15.5wt%Si alloy shows tensile strain of about 5 times greater than that of the gravity casting. Increase of the lattice parameter by rheocasting is due to the increased amount of Al dissolved in the primary Si crystal accelerated by shear stress at high temperature. The amounts of solute Al in the primary Si crystal are measured quantitatively by EPMA method to confirm the CBED analysis.
Al-6.2wt.%Si 합금의 등온교반시간에 따른 미세조직변화
이정일,박지호,김긍호,이호인 ( Jung Ill Lee,Ji Ho Park,Gyeung Ho Kim,Ho In Lee ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.5
N/A The microstructural evolution with isothermal stirring during semi-solid state processing of hypoeutectic Al-6.2wt%Si alloy was studied. Substructure of the individual primary solid particle in the slurry was investigated through transmission electron microscopy(TEM). Formation of subgrain boundaries on the rheocast Al-6.2wt%Si alloy is observed and the misorientation between the grains is shown typically under 2 degrees by analyzing selected area diffraction (SAD) and convergent beam electron diffraction (CBED) patterns. The existence of high angle grain boundaries are also observed in the alloy. Based upon these observations, mechanisms for the primary particles fragmentation are considered. With isothermal stirring, the dislocation density increases, and the evolution of dislocation cell structure takes place, which is interpreted as a process of achieving uniform deformation by dynamic recovery under applied shear stress.
수렴성 빔 전자회절법을 이용한 $SiC_p/Al$ 복합재에서의 계면 생성물의 상분석
이정일,이재철,석현광,이호인,Lee, Jung-Ill,Lee, Jae-Chul,Suk, Hyun-Kwang,Lee, Ho-In 한국현미경학회 1996 Applied microscopy Vol.26 No.1
A comprehensive methodology to characterize the interfacial reaction products of $SiC_p/2024$ Al composites is introduced on the basis of the experimental results obtained using XRD, SEM and TEM. XRD performed on the electrochemically extracted $SiC_p$ and bulk $SiC_p/2024$ Al composite have shown that the interfacial reaction products consist of $Al_{4}C_3$ having hexagonal crystallographic structure, pure eutectic Si having diamond cubic crystallographic structure, and $CuAl_2$, having tetragonal crystalloraphic structure, respectively. According to the images observed by SEM, $Al_{4}C_3$, which has been reported to have needle shape, has a hexagonal platelet-shape and eutectic Si is found to have a dendritic shape. In addition eutectic $CuAl_2$, was observed to form near interface and/or along the grain boundaries. In order to confirm the results obtained by XRD, the primitive cell volume and reciprocal lattice height of such interfacial reaction products were calculated using the data obtained from convergent beam electron diffraction (CBED) patterns, and then compared with theoretical values.
(Al2O3) p/6061 Al 복합재료의 계면반응 분석
이재철,이호인,이정일,김긍호 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.1
The interfacial characterization of Al alloy reinforced with Al₂O₃particulates was performed using X-ray diffraction and transmission electron microscopy. Layer of MgAl₂O₄ single crystals having octahedral shape was observed either at (Al₂O₃)_p/Al interface or near (Al₂O₃)_p. Based on the experimental observations and thermodynamic considerations, MgAl₂O₄ crystals formed at the surface of (Al₂O₃)_p are believed to grow by consuming Al₂O₃. Significant surface erosions of (Al₂O₃)_p around MgAl₂O₄ were also observed along a certain crystallographic orientation of (Al₂O₃)_p irrespective of the shape of MgAl₂O₄. Accompanying the interfacial reaction between Mg and Al₂O₃, reduction in precipates density was observed in the vicinity of Al₂O₃.
이재철,이호인,이정일 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.1
Characterization of the interface of SiC_p/Al composites was performed based on the experimental data obtained from X-ray diffraction, SEM, TEM, EDS, AES, and DSC. X-ray diffraction performed on the electrochemically extracted SiC_p showed that the interfacial reaction products consist of Al₄C₃ and pure Si having hexagonal and diamond cubic crystallographic structure, respectively. According to the experimental results obtained from the interfacial reaction products using SEM, TEM, and AES, Al₄C₃ was found to have a hexagonal plateletshape and Si is observed to exist as a dendritic pattern. Although severe interfacial reaction tends to occur at elevated temperature. Al₄C₃ and Si were found to form at the composite even at 450℃.
용탕단조한 (Saffil + C)/AC2B Al 복합재료의 계면반응
이재철,이호인,이정일,김기배 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.9
Interfacial reactions in squeeze cast AC2B Al alloy reinforced with Saffil and Carbon fibers were investigated using scanning and transmission electron microscopy, and secondary ion mass spectrometry. In the case of the as-cast composite, MgO crystals were observed in the vicinity of Saffil fibers. It indicates that the reaction occurred between SiO₂, which was used as a binder to fabricate the preform, and Mg present in the Al alloy during squeeze casting. In the case of T6 treated composite, however, very small MgAl₂O₄ crystals as well as MgO were observed at the surface of the Saffil fibers. Based on SEM and TEM study on the T6 treated composite, the interfacial reactions were observed to occur directly between Al alloy and SiO₂ binder to form both MgO and MgAl₂O₄ crystals. However, a direct reaction between the Al alloy and Saffil fiber were not observed to be significant in T6 treated composite.
Al-Si-Cu-Mg 계 용탕단조 합금의 미세조직과 기계적 성질
김문일,이호인,이정일,한소섭 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.10
The squeeze casting process is well known to yield superior cast products to those from gravity casting. New alloy systems of Al-Si-Cu-Mg which possess good castability and excellent mechanical properties have been examined to optimize cast alloy compositions. The alloy composition of Al-12wt%Si-3wt%Cu-0.7wt%Mg with and without Sr, Ti and B modifier was investigated in this study using brinell hardness, tensile strength and elongation. Tensile strength of 39 to 41 ㎏/㎟ and elongation of 1.7% to 2.5% was obtained from this squeeze cast alloy under T6 heat treament condition. These properties represent 10∼20% improvement over those from gravity cast products. Modification with Sr, Ti and B on this alloy resulted in 40% increase of elongation, although no significant change in wear resistance was found. Compared to AC8A and AC4CH alloys, Wear losses of this newly designed Al-Si-Cu-Mg alloy were reduced to 1/2 to 1/3, Abrasive wear tracks were mainly observed in this alloy, whereas both abrasive and adhesive wear tracks were found in conventional cast alloys.