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논문 : 표면처리 ; Mo기판에서 Si의 화학증착에 관한 연구
윤진국 ( Jin Kook Yoon ),정병성 ( Byoung Seong Jeong ),고흥석 ( Hung Suk Ko ),김재수 ( Jae Soo Kim ),최종술 ( Chong Sool Choi ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.7
Under deposition conditions limited by gas transport, the chemical vapor deposition of silicon on molybdenum substrate was investigated in the temperature range of 1173K and 1473K using hot-wall horizontal reactor and SiCl4-H2 gas mixtures. The deposition amount of silicon increased proportionally to the square root of total flow rate of reactants in which the outer layer of molybdenum substrate was pure silicon at 1173K, but to the quarter of that in which that was MoSi2 at 1473K. The deposition rate of silicon obeyed linear law at pure silicon but parabolic law at MoSi2. This suggested that the deposition rate of silicon was dependent on the concentration of silicon on substrate surface because the gaseous diffusion flux of reactants through a boundary layer was a function of that. This phenomenon was confirmed by the results obtained at 1298K that the deposition rate of silicon obeyed parabolic law below 4.3 hrs and changed linear law over 4.3 hrs.
자동차용 Al 합금 판재의 집합조직과 소성 이방성에 관한 연구
강석봉,고흥석,김형욱 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.12
The texture and plastic anisotropy of three different aluminum alloys (Al-Cu, Al-Mg and Al-Mg-Si) for auto body panel materials has been studied. In order to improve the formability of aluminum alloys, it is necessary to optimize the texture which gives rise to plastic anisotropy. The anisotropic properties were characterized by determining the R-values, and then compared to that calculated from quantitative texture data. The formability tests were also performed to obtain forming limit diagram(FLD) by using the stretching machine. Lankford parameter(R) values were predicted by the continuum mechanics of textured polycrystals (CMTP) method, which were compared with experimental R-values. The sheet having a random texture and a high n value showed an improved formability.
자동차용 Al-6 wt%Mg 합금에서 중간어닐링이 집합조직 발달에 미치는 영향
강석봉,고흥석,김형욱 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.8
The effects of intermediate annealing on the texture evolution were investigated in Al-6 wt%Mg alloy sheets for automobile application. Intermediate annealing was applied to controll the workability and texture in Al-Mg alloys. Textures were analyzed by using orientation distribution function method(ODF). The difference between ODFs at every manufacturing process was obtained by measuring differential orientation distribution function(DODF), which evaluted textures before and after hot rolling, intermediate annealing and T4 treatment. Intermediate annealing decreased the deformation textures, which had an influence on the development of recrystallization textures during final heat treatment.
Fe-Si-B 비정질 합금 세선의 결정화온도 및 융점에 미치는 반금속의 영향
최종술,문인기,고흥석,장준연 대한금속재료학회(대한금속학회) 1997 대한금속·재료학회지 Vol.35 No.12
The effect of metalloids on the crystallization temperature(T_x) and the melting point(T_m) has been investigated in Fe_(100)-○Si_xB_y, (2.5≤20, 2.5≤25, 10≤x+y≤35) alloy wires. The atomic size difference and heat of mixing of the alloys increased with increasing metalloid content. Conversely, the electron concentration decreased with the content. T_x of the Fe-Si-B amorphous alloy wires increased with the increasing values of the underlined three factors up to a maximum at a certain value of each factor. Then, the T_x decreased with those factors after the maximum. It is assumed that the change of T_x results from the variation of the relative stability of an amorphous phase with the heat of mixing which depends on the atomic size and electron concentration in alloys. The stability relies upon the elastic energy in a solid solution and the structural stability. The latter comes from the electron concentration effect, the former the atomic size difference. In contrast to T_x, T_m initially decreased with the three factors, then increased with them after showing a minimum although the relation showed much more divergence than that of T_x. Since the maximum of T_x and the minimum of T_m occur at the nearly same values of heat of mixing, T_x/T_m(glass forming ability) has a maximum in the vicinity of these heat of mixing values.
변태 속도론에 의한 Fe-Si-B 합금 세선의 비정질 형성능 예측
최종술,문인기,고흥석 대한금속재료학회(대한금속학회) 1996 대한금속·재료학회지 Vol.34 No.10
The glass forming ability. GFA, has been investigated experimentally and predicted from the transformation kinetics in Fe-Si-B alloy wires. The critical diameter for the formation of an Fe-Si-B amorphous wire increased with the metalloid content up to the amount of 25 at%, then decreased over that content. The amorphous alloy wire with the largest critical diameter has shown the highest value of crystallization temperature at the composition of Fe_(15)Si_(10)B_(15). The larger the diameter of an amorphous wire was, the lower the critical cooling rate that was predicted from the transformation kinetics. The kinetic approach for the prediction of the glass forming ability was successful in view of a good agreement of the measured GFA with the predicted one.
박종우,문인기,고흥석,장준연 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.10
Cast structures of Ti-Al alloys containing 44, 48, and 52 at.% Al, respectively, were studied after casting at different cooling rates. In 44 at.% Al alloy, slowly cooled structure consisted of fully lamellar grains of α₂and γ whereas in fast cooled one lamellar formation was considerably suppressed, so that supersaturated α₂phases with A.P.D. (Anti-Phase Domain) structures were predominantly formed. In 48 at.% Al alloy dendritic lamellar grains were the major constituent with gamma phase as interdendritic segregates. Lamellar grains became finer with faster cooling. Dendritic lamellar grains transformed from primary α were distributed within the matrix of γ in 52 at.% Al alloy. Isolated γ islands were observed inside of the lamellar grains in slowly cooled 52 at.% Al alloy. Primary phase during solidification seems to be β in 44 at.% Al alloy, while α seems to be a major primary phase in 48 at.% Al alloy.
박종우,문인기,고흥석 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.2
Microstructural observations and mechanical tests were carried out to clarify the causes of frequent crack occurrence of leaded nickel silver cast structure during cold rolling. Interdendritic micropores in cast structure are believed to be the major causes of the failures. High hydrogen gas absorbing power of this high nickel bearing alloy may lead to the formation of the micropores, when degassing is insufficient. This supposition was further supported by the comparison of tensile and impact test results of fully degassed specimens with those of insufficiently degassed specimens.
자동차용 Al-6 wt%Mg 합금에서 중간어닐링이 소성이방성에 미치는 영향
홍순형,강석봉,고흥석,김형욱 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.6
The effects of intermediate annealing on the plastic anisotropy were investigated in Al-6 wt%Mg alloy sheets for automobile application. Intermediate annealing was adopted to improve the formability in Al-Mg alloys. For two different conditions of O and T4 treatment, textures were analyzed by using orientation distribution function method. The plastic anisotropy properties were evaluated by measuring R values, and then compared them with caculated R values from quantitative texture data. The stretch forming properties were also evaluated by using work hardening exponents. Intermediate annealing decreased the deformation textures, which had an influence on the development of recrystallization textures during final heat treatment. Isotropy and stretch forming properties were decreased in the axis of 45˚ to rolling direction for O treatment due to highly remained deformation textures. Whereas anisotropy and stretch forming properties were increased in the axis of 45˚ to rolling direction for T4 treatment due to well-developed recrystallization textures of rotated cube along normal direction.
Al-Mn-Mg 합금에서 냉간압연과 중간소둔처리가 귀율에 미치는 영향
이주원,강석봉,고흥석,이정무 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.9
Texture and deep drawability have been investigated in Al-Mn-Mg alloy by means of orientation distribution functions(ODFs) analysis. The effect of heat treatment and cold rolling on texture varied with the process variables. Intermediate annealing before final cold rolling led to the formation of cube texture and 0°/90°earing. While, the variation of cold rolling ratio can balance the proportion of the recrystallization texture to the deformation texture so that the overall anisotropy is minimized. In the specimens cold rolled directly after hot rolling, cold rolling had more influence on earing rate than intermediate annealing. On the contrary, intermediate annealing exerted more effect on earing rate than cold rolling in the specimens intermediate annealed directly after hot rolling.
Pack Siliconizing 공정에 의한 MoSi2 코팅층의 성장기구
김재수,최종술,고흥석,윤진국 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.8
The growth mechanism of MoSi₂ coatings formed by the pack siliconizing of molybdenum was investigated in the temperature range of 1223K∼1473K. Experiments were conducted under an argon atmosphere using 40Si-5NaF-55Al₂O₃ in weight percents packs. The results clearly revealed the following novel phenomenon : when packs were kept at a constant temperature, the growth rate of MoSi₂ coating was proportional to time at early stage, but at later stage the growth was changed to parabolic function of time. In order to interpret the phenomenon, a model was proposed under the assumption that chemical reaction for MoSi₂ formation at MoSi₂/Mo interface were responsible for the early stage growth. As a result, it was understood that the growth at early stage was controlled by chemical reaction and the later stage growth controlled by the mass balance conditions of gas and solid diffusions. Thus, two kinds of activation energy were obtained ; one with the value of 240 KJ/mole was considered as the linear growth rate constant, k₁, (㎝/sec), and the second with the value of 1.93 KJ/mole was about the parabolic growth rate constant, k_p(㎠/sec).