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Al-Li-(Be) 합금 주괴의 미세조직과 기계적 성질
은일상,조현기 ( Il Sang Eun,Hyun Kee Cho ) 한국주조공학회 1990 한국주조공학회지 Vol.10 No.5
N/A The purpose of this study is to investigate the effect of Be addition on the microstructure and mechanical properties of as-cast and homogenization treated Al-Li-(Be)alloys. The ductility of as-cast Al-Li alloy was increased by the addition of Be and the fracture morphology was changed from brittle to ductile mode. Also, hardness and strength have been decreased by homogenization treatment. The morphology of eutectic structure which consists of α(Al) and α(Be) was changed from lammellae to spherical type by homogenization treatment. The shape of α(Be) phase has been revealed as hollow type by TEM observation. It consists of outer surfaces with well defined crystal facets and the core filled with α(Al). The microstructure of as-cast Al-Li-Be alloys showed coarse δ´, fine δ´, and coarse δ phases. The coarse and fine δ` phases were formed at Be-rich phase /matrix interfaces and in matrix, respectively. By homogenization treatment, the δ phase in Al-Li and Al-Li-Be alloys dissolved and the size of δ phase in Al-Li-Be alloys was finer than that of Al-Li alloy.
Fe₃O ₄-Al₂O ₃-CaO系 鑛球의 還元에 關한 硏究
양훈영,이승원,김진호,은일상 연세대학교 산업기술연구소 1975 논문집 Vol.6 No.1
Reduction of coke mixed magnetite ore pellets containing alumina and/or lime has been carried out in a fixed bed with coke powder in the temperature range of 1,100-1,250℃. Degree of metallization of the reduced pellets was obtained from the chemical analysis, and volume change of the reduced pellets was evaluated by measuring pellet diameter before and after reduction. Phase change during the reduction was also investigated by microscopic observation. The results obtained are summurized as follows. (1) As the Al₂O ₃content increases, degree of metallization of the ore pellets decreases and shrinkage of the reduced pellets also decreases. (2) Addition of 5% CaO to the 5% Al₂O ₃ pellets improves the degree of metallization and increases shrinkage of the reduced pellets, especially within the temperature range of 1,200-1,250℃. In the case of 10% CaO addition to the same pellets, however, both degree of metallization and shrinkage decrease. (3) CaO addition to the 10% Al₂O ₃ pellets showed the similar effect to that of 5% Al₂O ₃ pellets on the degree of metallization and shrinkage, showing no conspicuous effect of lime addition. (4) While Al₂O ₃ in the pellets is inhibitive to the reducibility as well as agglomeration, CaO is promotive to the above properties.
양훈영,은일상,이승원 대한금속재료학회(대한금속학회) 1976 대한금속·재료학회지 Vol.14 No.5
球狀黑鉛鑄鐵의 表綿硬度와 耐磨耗性을 개선하기 위한 表面硬化法으로서 浸硼處理의 適用可能性 與否를 조사할 목적으로 이 실험을 실시하였다. 球狀黑鉛鑄鐵을 Si 含量을 변화시켜 熔製하고 이것을 黑鉛化燒鈍處理하여 그 基地組織과 硬度를 조사하였으며 이러한 鑄鐵을 Borax+22%B₄C+8%NH₄Cl의 混合熔融鹽浴 중에서 液體法으로 浸硼處理하여 Si量과 基地組織의 변화에 따른 浸硼擧動을 조사하고 表面硬度와 耐磨耗性을 測定하였다. 浸硼層은 Fe₂B를 주로 한 鐵硼化物層과 硼炭化物의 析出相을 포함하는 硼素固溶擴散層으로 형성되었으며 鐵硼化物層의 깊이는 鑄放狀態에서 보다는 pearlite化 및 ferrite 化燒鈍을 함으로써 어느 정도 증가되었으나 Si量의 증가에 따른 변화는 경미하였다. 또한 硼素固溶擴散層은 Si 量의 증가에 따라 硬度가 증가되었다. Si 含量이 많은 경우에는 鐵硼化物層 다음에 黑鉛集積層이 형성되어 浸硼層剝離의 원인이 되었으며, 鑄放狀態에서 基地 중에 Fe₃C가 많은 것을 浸硼處理하였을 때는 鐵硼化物內에 黑鉛이 늘어난 상태로 散在하여 硬度低下의 원인이 되었다. 高 Si(2.45%)의 球狀黑鉛鑄鐵을 제외하고는 浸硼處理에 의하여 表面硬度와 耐磨耗性이 현저하게 증가되었다. The aim of this experimental work is to find out the possibility of boronizing of spheroidal graphite cast iron (SGCI) in order to improve surface hardness and wear-resistivity. Samples with various silicon content were prepared in a Kryptol furnace and heat-treated to obtain the pearlitic or ferritic matrix. Liquid boronization in a molten bath containing borax, boron carbide and ammonium chloride was carried out with these samples having different silicon content and matrix. The boronized layer consisted of iron boride layer and boron-diffused layer, the former was mainly Fe₂B and the latter contained the precipitated phase of boro-carbides. The depth of the iron boride in the annealed matrix was increased to a certain extent rather than in the as-cast matrix, but its change with silicon content was not remarkable, Hardness of the boron-diffused layer was increased as the silicon content increases. In the case of high silicon content, graphite accumulated zone was formed beneath the iron boride layer, resulting in tearing off the iron boride layer. When as-cast structure containing cementite was boronized, elongated graphites appeared sporadically in the iron boride, causing the decrease of hardness. Both surface hardness and wear-resistivity of the boronized SGCI, except for high silicon contained, were improved remarkably.
조현기,은일상,유병호,박수동,백정우 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.8
For the purpose of ameliorating of toughness by boundary control, Be was added to Al-Li multiphase alloys. Interface behaviors during ageing were investigated by means of the measurements of hardness and tensile strength, and also the observation of optical and transmission electron micrographs. In order to evaluate the fracture toughness, instrumented Charpy impact test was carried out and fracture surface was observed with a scanning electron micrograph. Grain size was refined by α-Be particles that acted on dragging force at grain boundary in Al-Li-Cu-Be alloy. And PFZ half width in Al-Li-Cu-Be alloy was decreased by early precipitation of T₁ phases compared with Be-free alloy. Double eak phenomenon which was observed at the hardness and tensile tests in Al-Li-Cu-Zr-Be alloy may be estmated by the precipitation of secondary T₁ phases due to the change of δ′, T₁ and θ′ phases stability. And considering toughness and elongation, it is possible to think that the secon peak condition may be the most optimum condition of heat treatment because of the remarkable improvement of elongation in Al-Li-Cu-Zr-Be alloy. In case of Al-Li-Cu-Zr alloy containing minor Be, higher impact absorbed energy than that of Be-free alloy was observed. This remarkable improvement of fracture toughness was attributed to the change of fracture mechanism from brittle to ductile mode. the high energy fracture mode of minor Be added alloy was associated with homogeneous deformation due to various interface controls.
7175Al 단조재의 강도와 인성에 대한 불순물과 제조공정의 효과
박중근,은일상,서인식,임성택 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.3
The effects of impurity content and of fabrication processes on the tensile properties and toughness of 7175 Al forgings have been studied using conventionally processed 7075 and 7175 Al forgings and a specially processed 7175 Al forging. A specially processed 7175 Al forging was superior to a conventional 7075 Al forging in both the strength and toughness. These beneficial effects primarily arise from two effects, i.e., the effect of reduction of impurity level and that of application of special fabrication procedures. The reduction of impurity level of Fe and Si has significantly diminished the number of constituent particles containing Cu and Mg. A further reduction of the number of constituent particles has been observed on applying specially designed fabrication process. The reduction of impurity level exerts no significant effect on the dispersion of Cr and Mg containing E phase. However, the application of special fabrication processes results in a coarsening of E phase. This is believed to have an effect to promote a finer grain structure, which may also contribute to the enhancement of strength and touhgness of the alloy.