분사주조한 SiCp 입자강화 알루미늄 복합재료의 미세조직과 마멸특성

박종성,김명호 ( Chong Sung Park,Myung Ho Kim ) 한국주조공학회 1995 한국주조공학회지 Vol.15 No.6

N/A The SiC_p-reinforced preforms fabricated by spray casting process were hot-extruded and subsequently T6-treated, and the morphology of the silicon phase and the grain size for these preforms and extruded samples were examined by Image Analyzer. Experimental observation revealed that with increase in volume percent of SiC particles, the grain size and silicon phase of the Al-Si/SiC_p composites become finer, the shape of Si phase is changed from blocky to granular type, and aspect ratio of Si phase tend to become unity. Wear-tests with various sliding velocities, show that the wear resistance of spray cast specimen is increased remarkably compare to the permanent mold cast specimen at the sliding velocity range of 1.98∼2.38m/sec.. Microstructural observations for the worn surfaces of specimens revealed that wear resistance of Al-Si alloys at certain sliding velocities could be improved not only by the fine grain size of aluminum matrix but also the fine size and granular shape of silicon phases. The wear resistance of SiC_p reinforced aluminum composites was found to be sensitive to the volume percentage of the reinforcing particles. The worn surfaces with various sliding velocities, show that change in wear mechanism seems to occur at the sliding velocity of near 2m/sec for all samples, and such a change in mechanism is delayed with increase in SiC_p volume fraction.

분사주조한 입자강화 알루미늄 복합재료의 미세조직 특성

박종성,이인우,김명호 ( Chong Sung Park,In Woo Lee,Myung Ho Kim ) 한국주조공학회 1994 한국주조공학회지 Vol.14 No.6

N/A Aluminium-silicon alloy(JIS AC8A) matrix composites reinforced with SiC particles were fabricated by spray-cast forming process, and the microstructure of powders and preforms produced were studied by using an optical and scanning electron microscopy. SiC particles were co-sprayed by mixed phase injection method during the spray casting process. Most of the composite powders formed by this mixed phase injection method exhibit morphology of particle-embedded type, and some exhibits the morphology of particle attached type due to additional attachment of the SiC particles on the surface of the powders in flight. The preforms deposited were resulted in dispersed type microstructure. The pre-solidified droplets and the deposited preform of SiC-reinforced aluminium alloy exhibit finer equiaxed grain size than that of unreinforced aluminium alloy. Eutectic silicons of granular type are crystallized at the corner of the aluminum grains in the preforms deposited, and some SiC particles seem to act as nucleation sites for primary/eutectic silicon during solidification. Such primary/eutectic silicons seem to retard grain growth during the continued spray casting process. It is envisaged from the microstructural observations for the deposited preform that the resultant distribution of SiC injected particles in the Al-Si microsturcture is affected by the amount of liquid phase in the top part of the preform and by the solidification rate of the preform deposited.

주조용 A356 합금에서 Fe 계 금속간화합물의 형상에 미치는 Be 의 영향

이정근,박종성,김명호 ( Jeong Keun Lee,Chong Sung Park,Myung Ho Kim ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.4

N/A Microstructure of A356 aluminium alloys cast in a permanent mold was investigated by optical microscope and image analyzer, with particular respect to the shape and size distribution of iron intermetallics known as β-phase (Al_5,FeSi). Morphologies of the β-phase was found to change gradually with the Be:Fe ratio like these. In Be-free alloys, β-phase with needlelike morphology was well developed, but script phase was appeared when the Be:Fe ratio is above 0.2:1. With the Be:Fe ratios of 0.4:1-1:1, script phase as well as Be-rich phase was also observed. In case of higher Be addition, above 1:1, Be-rich phase was observed on all regions of the specimens, and increasing of the Be:Fe ratios gradually make the Be-rich phase coarse. It was also observed that the β-phase with needlelike morphology was coarsened with increase of the Fe content in Be-free alloys. However, in Be-added alloys, length and number of these β-phases were considerably decreased with the increased Be:Fe ratio. It was concluded that Fe impurity element to be crystallized into needlelike intermetallics was tied up by Be addition element, and new phases were crystallized into script or Be-rich intermetallics. (Received January 23, 1998)

저압주조품의 미세조직과 기계적 성질에 미치는 금형온도의 영향

이정근,박종성,김명호 ( Jeong Keun Lee,Chong Sung Park,Myung Ho Kim ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.3

N/A Microstructure and mechanical properties of the low pressure die-cast Al wheels were investigated by microscope, image analyzer, NDT (non-destructive test), and tensile test. The variation of SDAS (secondary dendrite arm spacing), porosity per unit area, quality grade, and tensile properties with the mold temperatures were examined. SDAS was gradually decreased with a decrease in temperature. However, the lowest value of porosity per unit area was observed at the mold temperature of 405˚C and the optimum mold temperature was found to be 405˚C. Besides, from the observation of pore morphology, it was also found that the pore formation was mainly caused by shrinkage during solidification. The tensile strength, elongation, and impact toughness were markedly decreased, however the yield strength was nearly constant. The decrease of mechanical properties is attributed to the increase of porosity. (Received January 23, 1998)

과공정 Al-Si 합금의 열팽창거동과 기계적 성질에 미치는 미세조직의 영향

박종성,이정근,김명호 ( Chong Sung Park,Jeong Keun Lee,Myung Ho Kim ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.4

N/A The egects of changes in microstructure of Si phase on the thermal expansion coefficients(CTEs) and tensile properties of the hypereutectic Al-Si foundry alloy(A390) were investigated experimentally. Specimens were prepared by various fabrication processes, such as a permanent mold casting, a squeeze casting and a spray casting process, and subsequently hot-extruded. CTEs of the spray-cast specimen were found to be about 10% lower than those of the permanent mold-cast specimen, and the CTEs of the hypereutectic Al-Si alloy(A390) were changed proportionally with the size of Si phase. Ultimate tensile strength of the spray-cast and hot-extruded specimen was dramatically improved about 100% with improved elongation, compared to that of permanent mold-cast specimen. These improvements are mainly attributed to the reduction in size and aspect ratio of the brittle Si phase, and the elimination of the microvoids/porosities formed during casting.

금형소재용 동합금의 미세조직 및 기계적 성질에 미치는 첨가원소의 영향

배진호,박종성,김명호 ( Jin Ho Bae,Chong Sung Park,Myung Ho Kim ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.3

N/A Effects of Si and Ni addition on the microstructure and mechanical properties of the Cu-12wt.%Al-5wt.%Fe-1wt.%Mn alloy have been investigated experimentally. Microstructure of the as-cast specimen is found to be refined markedly by additions of Ni and Si. By the addition of Ni, volume fraction of the k phase is increased, but volume fraction of the y phase is decreased. Hardness is increased with the addition of Ni, due to increasing of k phase which is harder than y phase. However, Charpy impact value is not significally decreased possibly due to the formation of isolate k phase. (Received February 19, 1998)

고크롬 백주철의 미세조직과 기계적 특성에 미치는 첨가원소 Ti 의 효과

권진업,박종성,김명호 ( Jin Up Kwon,Chong Sung Park,Myung Ho Kim ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.1

N/A The effects of Ti addition on the microstructure and mechanical properties of high chromium white cast iron were investigated mainly with respect to the shape and size of carbides. Heterogeneous mixtures of the randomly-oriented bundles of eutectic carbides and the primary carbides with coarse hexagonal morphology were observed in the unmodified as-cast white cast irons. However the size and aspect ratio of these carbides were dramatically decreased by Ti addition resulting in improved impact toughness. Based on the observations of the effects of austenite contents, the size of carbides, and its aspect ratio on the impact toughness, it was concluded that the most effective factors of toughness improvement were the size and the aspect ratio of carbides, and these factors could be moified by Ti addition and control of cooling rates. (Received October 24, 1997)

급속응고한 Al-Mg 합금의 미세조직 및 인장특성에 미치는 첨가원소의 영향

박현호,박종성,김명호 ( Hyun Ho Park,Chong Sung Park,Myung Ho Kim ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.4

N/A In order to study effects of Cu and lie on the microstructure and tensile properties of rapidly solidified Al-Mg alloys, Al-Mg-Cu-Be alloys have been rapidly solidified by inert gas atomization process. Microstructure of rapidly solidified Al-Mg-Cu-Be powders exhibited refinement and good dispersion of Be particles as increasing of solidification rate. Solidification rate of atomized powders was estimated to be about 5 × 10^(3n)C/s. Inert gas atomized Al-Mg-Cu-Be powders were hot-processed by vacuum hot pressing at 450℃ under 100 MPa and hot extruded with reduction ratio in area of 251 at 450℃. The extruded Al-Mg-Cu-Be. powders consisted of recrystallized fine A1 grains and homogeneously dispersed fine Be particles, and exhibited improved tensile properties with increase in Cu content. Al₂CuMg compounds precipitated in grain and grain boundaries of Al-Mg-Cu-Be alloys with aging heat treatment after solution treatment. Hardness and tensile properties were improved by increasing Cu content and Be addition. Compared with extruded Al-Mg-Cu powders, the extruded Al-Mg-Cu-Be powders exhibited finer recrystallized grains and improved tensile properties by dispersion hardening of Be and subgrain boundaries pinned by fine Be particles. After aging treatment, hardness and tensile properties were improved due to restricted precipitation by increasing of dislocation density around Be particles in matrix.

분사주조법에 의한 저열팽창 알루미늄합금의 제조

박종성,이정근,김명호 ( Chong Sung Park,Jeong Keun Lee,Myung Ho Kim ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.3

N/A In order to fabricate lower thermal expansion aluminium alloys, the effects of microstructural parameters such as the volume fraction of SiC_p and the shape and size of Si phase on the coefficient of thermal expansion(CTE) of the spray-cast and hot-extruded hypereutectic Al-Si(A390) alloy composites were investigated experimentally. The CTEs of hypereutectic Al-Si (A390) alloy were changed proportionally with the size of Si phase. Ultimate tensile strength, elongation and Young`s modulus of the spray-cast and hot-extruded specimen were improved dramatically compared to those of the permanent mold-cast specimen. Although Young s modulus of the spray-cast and hot-extruded specimen was improved highly effectively by addition of SiC_p, no improvement was observed for the UTS and elongation. Spray-cast and hot-extruded hypereutectic Al-Si (A390) alloy reinforced with 20vol.%SiC_p exhibits a CTE equivalent to stainless steel.

Cymbal Type 압전 발전기의 발전 특성

전호익,정성수,정현호,박태곤,김명호,Jun, Ho-Ik,Jeoung, Sung-Su,Chong, Hyon-Ho,Park, Tae-Gone,Kim, Myung-Ho 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.4

On this paper, piezoelectric generators using piezoelectric ceramics were designed and fabricated. Generators were made by attaching cymbal type metal plates on upper and bottom sides of a disc type piezoelectric ceramic. Generator converts wasting mechanical energy to electrical energy. Output voltage was increased when thickness of ceramic and displacement of vibration were increased. Temperature of the ceramic was increased when it generates, but the temperature rising was saturated at certain temperature.