• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.236-240
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• 2007

In order to control the microstructure of amorphous/crystalline composites, gas atomized $Cu_{54}Ni_{6}Zr_{22}Ti_{18}$ metallic glass powders wrapped in a crystalline brass were extruded repeatedly. The size of microstructure in the resultant composites was varied depending on the pass of extrusion as well as on the area reduction ratio. The microstructure could be estimated using an equation of $r_n=r_{n-1}/R^{1/2}$, where R is reduction ratio and $r_n$ is the resultant radius of the extruded bar after n pass. Theory of microstructural refinement as well as the relationship between the resultant microstructures and mechanical properties was discussed.

• 한국분말재료학회지
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• 제5권2호
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• pp.122-128
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• 1998

NiAl based ODS (Oxide Dispersion Strengthened) intermetallic alloys have been produced by mechanical alloying (MA) process and consolidated by hot extrusion. Subsequent thermomechanical treatments have been applied to induce secondary recrystallization in an attempt to improve creep resistance in this material. The creep behavior of secondary recrystallized MA NiAl has been investigated and compared with those of as-extruded condition. Minimum creep rate were shown to be approximately two orders of magnitude lower than that in as-extruded condition. The improvement in creep resistance is believed due to the grain coarsening, restricting of dispersoid coarsening as well as increase in grain aspect ratio. Creep threshold stress behavior, below which no measurable creep rate can be detected, has been discussed on the basis of particle-dislocation interaction theory. The threshold stress becomes negligible after secondary recrystallization in MA NiAl, presumably due to dispersoid coarsening and a decrease in grain boundary area during secondary recrystallization.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1992년도 추계학술발표강연 및 논문개요집
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• pp.14-14
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• 1992

During the past five years a very successful effort has been made to improve existing and develop new aluminium alloys. The progress achieved has been possible because of the development of new production methods, such as powder metallurgy and spray/deposition. These methods make use of rapid solidification process which alloys compositions other than those achieved by conventional ingot metallurgy. The ingot metallurgy of the 2000 and 7000 series used thus far, as well as the age hardening Al-Li alloys, show several disadvantages caused by the production process. Such problems are primarily coarse intermetallic constituent phases, coarse grains and macrosegregation, resulting in low fracture toughness. The present contribution reports results of an experimental investigation performed on a modern high strength spay deposited aluminium alloy of the Al-Zn-Mg-Cu (7075 and the modified 7150X) type. Results are given in terms of its microstructural characterization by using X-ray diffractomertry and transmission electron microscopic. The mechanical propierties of those alloys in the as-extruded and extruded+aged condition were evaluated by using microhardness Vickers, tensile test and fracture toughness measurements.

• Applied Biological Chemistry
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• 제33권3호
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• pp.209-215
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• 1990

압출면의 영양강화 목적으로 대두분을 소맥분과 섞어 점도 특성을 고찰하고, 압출면을 제조할 후 조리시험, 조리면의 조직감시험 및 관능정사 결과 대주분 첨가비율이 증가함에 따라 복합분의 점도, 조리면의 조직감 및 조리품질은 저하하였다. 대두분 10% 첨가 압출면에 각종 첨가제의 첨가효과를 보면, 첨가제의 첨가량이 증가함에 따라 점도는 증가하였으며, 첨가제 중에서는 xanthangum이 가장 효과적이었다. 조직감에 있어서는 Na-carboxymethyl cellulose 2.0%, guar gum 2.0%, xanthan gum 1.0%에서 밀가루면과 비슷한 값을 나타내었으며, 관능검사도 이와 유사한 결과를 보였다.

• Applied Biological Chemistry
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• 제33권3호
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• pp.216-222
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• 1990

압출면의 영양강화 목적으로 두유박을 제면 원료인 소맥분과 섞어 점도 특성을 고찰하고, 압출면을 제조한 후 조리시험, 조리면의 조직감 시험 및 관능검사를 통하여 알아본 결과 두유박 첨가 비율이 증가함에 따라 복합분의 점도, 조리면의 조직감 및 조리 품질은 감소하였다. 두유박 10% 첨가 압출면의 제면 특성을 향상시키기 위하여 각종 첨가제의 첨가효과를 보면, 첨가제의 첨가량이 증가함에 따라 점도는 증가하였으며, 첨가제중에서는 xanthan gum이 가장 효과적이었다. 조직감에 있어서는 Na-alginate 2.0%, Na-carboxymethyl cellulose 2.0%, guar gum 0.5%, xanthan gum 1.0%가 좋을 결과를 나타내었다. 관능검사도 이와 유사한 결과를 보였다.

• 동력기계공학회지
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• 제20권6호
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• pp.40-45
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• 2016

The manufacturing process of large scaled Al 7050 alloy is difficult for the occurrence of solidification crack during casting. The aims of this study are the evaluations of microstructure and mechanical properties of extruded Al 7050 billet and ring forged one with large scale. Large scaled Al 7050 billet was casted by direct-chill casting process. The extruded and ring forged specimens were prepared from the casted ingot after residual stress relief and homogenization heat treatment, respectively. Microstructures, hardness and tensile test of the surface, middle and center part of each specimen were performed at room temperature. Sheared and elongated type grains were observed at the edge parts of surface and center area and its aspect ratios of grains were low and similar as 0.21 while that of middle area was closed to 0.92 value in ring forged Al 7050 alloy. The mechanical properties of extruded Al 7050 alloy were superior than those of ring forged one. The hardness values of surface and center part were slightly higher than that of middle part in ring forged Al 7050 alloy.

• 한국양식학회지
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• 제10권2호
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• pp.163-169
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• 1997

사료물성과 단백질원 배합비에 따른 조피볼락의 성장차이를 구명하기 위하여, 실험사료의 단백질원을 북양어분과 갈색어분으로 한 사료와 경제적인 측면을 고려하여 어분의 배합 비율을 낮추는 대신, 대두박, 콘글루텐 밀, 육분 및 우모분의 비율을 늘린 2종의 사료를 설계하여, 각각 EP(extruded-floating pellet, 부상사료), SP(slow-sinking pellet, 반부상사료), FP(fast-sinking pellet, 침강사료)와 MP (moist pellet, 습사료) 형태의 배합사료를 제조하였다. 평균체중 75 g의 조피볼락을 각 수조에 50마리씩 수용하여 $2(diet\times)4(diet type)\times3(replication)$ factorial design으로 15주간 사육하였다. 사육 실험한 결과, 실험사료와 사료형태에 따른 최종평균체중, 증체율, 사료효율, 사료 섭취율, 단백질 효율, 간중량비 및 내장중량비는 전혀 차이가 없는 것으로 나타났다(P>0.05). 실험 종료시의 실험 구별, 어체 부위별 일반성분 중에 사료별, 사료 형태별로 모두 간과 근육의 단백질 및 근육의 수분과 지질 함량은 실험구간별로 유의적인 차이가 없었다(P>0.05). 위와 같이 사료의 물성이나 침강 속도는 조피볼락의 성장, 영양소 이용효율, 사료 섭취율 및 체성분에 영향을 미치지 않은 것으로 나타나, 양식 현장에서 사료 형태에 관계없이 적절히 선택하여 사용할 수 있을 것으로 전망된다.

• 한국식품과학회지
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• 제33권1호
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• pp.55-59
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• 2001

쌀의 팽화에 관한 연구는 팝콘에 관한 연구와 비교하면 매우 미흡한 편이다. 쌀을 팽화시킬 때 대부분 가압식 팽화기나 압출성형기를 이용하고 있다. 대부분의 쌀의 팽화에 관한 연구는 인도에서 이루어져 왔으며, 가공조건(수분함량, 가열온도) 등이 팽화쌀의 물리화학적 성질에 관한 연구가 대부분이다. 팝콘과 같은 인스턴트 팽화쌀의 팽화기작 및 개발에 관한 연구는 극히 제한되어 있다. 압출성형 팽화펠릿의 팽화에서 3일 수침 후 분쇄한 찹쌀을 이용하여 수분함량 $20{\sim}27%$, $CO_2$ 가스주입압력 2.8 MPa, 스크류회전속도 200 rpm으로 제조한 펠릿을 microwave oven에서 팽화시 밀도와 조직감이 비교적 낮게 나타나는 경향을 보였다. 또한 압출성형기로 제조된 펠릿의 팽화시 가장 큰 영향인자는 펠릿의 수분함량과 가스주입압력, 스크류회전속도의 조절에 의해 팽화 및 조직감을 최적화 할 수 있었다.

• 한국주조공학회지
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• 제17권4호
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• pp.356-364
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• 1997

In order to study effects of Cu and Be 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 $5{\times}10^{3{\circ}}C/s$. Inert gas atomized Al-Mg-Cu-Be powders were hot-processed by vacuum hot pressing at $450^{\circ}C$ under 100 MPa and hot extruded with reduction ratio in area of 25: 1 at $450^{\circ}C$. The extruded Al-Mg-Cu-Be powders consisted of recrystallized fine Al grains and homogeneously dispersed fine Be particles, and exhibited improved tensile properties with increase in Cu content. $Al_2CuMg$ 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.

• 소성∙가공
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• 제33권3호
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• pp.178-184
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• 2024

In this study, we investigated the effects of extrusion ratio and extrusion temperature on the microstructure and tensile properties of extruded Mg-6Al-0.3Mn-0.3Ca-0.2Y (SEN6) alloy. As the extrusion ratio and temperature increase, dynamic recrystallization during extrusion is promoted, leading to the formation of a fully recrystallized microstructure with increased grain size. Additionally, the increases in extrusion ratio and temperature lead to texture strengthening, exhibiting a higher maximum texture intensity. The extruded materials contain three types of secondary phases, i.e., Al₈Mn₄Y, Al₂Y, and Al₂Ca, with irregular or polygonal shapes. The quantity, size, distribution, and area fraction of the second-phase particles are nearly identical between the two materials. Despite its larger grain size, the tensile yield strength of the material extruded at 450 ℃ and an extrusion ratio of 25 (450-25) is higher than that of the material extruded at 325 ℃ and an extrusion ratio of 10 (325-10), which is mainly attributed to the stronger texture hardening effect of the former. The ultimate tensile strength is similar in the two materials, owing to the higher work hardening rate in the 325-10 extrudate. Despite differences in grain size and recrystallization fraction, numerous twins are formed throughout the specimen during tensile deformation in both materials; consequently, the two materials exhibit nearly the same tensile elongation.