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설경원,박영구 全北大學校 1984 論文集 Vol.26 No.-
Grain growth in solid materials is simulated by LSW theory. First, the performance of this program is tested as follows. According to LSW theory, the size distribution becomes stationary time-independent one after some time from the beginning of growth whatever the initial size distribution is. So whether the simulated distribution will converge to the theoretical one is verified by CHI-SQUARE TEST using Gaussian distribution as initial distribution. After this verification, abnormal grain growth is simulated for 1st order reaction controlled system, 2nd order reaction controlled system, and for diffusion controlled system. In this simulation, large grains (about 3-5 times larger than the grain which has maximum size) are presented intentionally and the behavior of this system is observed. The result is that the abnormal grain growth can be occurred by initial size fluctuation.
설경원,우기도 전북대학교 공업기술연구소 1985 工學硏究 Vol.16 No.-
The effects of composition and liquid volume fraction on the density in heavy alloys have been studied. The specimens have been sintered at 1450℃ in hydrogen atmosphere. The relative density of W-Ni-Fe system is higher than that of W-Ni-Cu system and this tendency is increased with Cu content. Liquid volume fraction promotes the densification in W-Ni-Fe system.
중성자회절에 의한 WC-Ni 복합재료의 잔류 열응력 측정
설경원 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.5
The differential thermal residual stress state in WC-6wt.%Ni and WC-25wt.%Ni cemented carbide composites has been studied using neutron powder diffraction. Residual strain values have been obtained from the difference in WC cell parameters in a strain-free WC powder and in the composites over the temperature range 100-900 K. The nature of stress state of WC phase in the as-produced composite was confirmed to be hydrostatic by tri-axial stress measurements. The stress state is compressive in the WC phase and tensile in the Ni binder phase as expected. The absolute stress value increases as the temperature decreased and as binder content increased. The effective stress set-up temperatures are about 1030 K for low binder composite and 990 K for high binder composite.
설경원,Seol, Gyeong-Won 한국재료학회 1994 한국재료학회지 Vol.4 No.2
Ni기 초합금은 Co, Cr, Mo, W등의 고용 강화 원소와 AI, Ti, Nb, Ta 등의 $\gamma '$ 석출 강화 원소로 구성되어 있다. 초합금의 기계적 성질과 내산화성을 개선하기 위하여 희토류 원소를 재료 내부에 첨가하거나, 코팅 재료로써 사용하고 있다. 이들 희토류 원소는 $Al_2O_3, Cr_2O_3$등의 산화물의 종류에 따라 산화물의 성장 속도와 밀착성에 영향을 미친다. Hf함유 Ni기 초합금 AF115와 $AI_2O_3$ 함유 MA6000초합금 2종을 이온 코터를 이용, Yttrium 표면개질후, 온도 1273K-1473K에서 고온 산화 수 산호 피막의 성장 속도, 결정립, 내부 구조 및 내박리성에 미치는 Yttrium 의 영향을 조사하였다. AF115와 MA6000 초합금에 Yttrium코팅을 한 결과 내부 산화물의 성장에 현저한 변화가 있었다. Yttrium의 표면 개질에 의하여, AF115의 경우는 $AI_2O_3$ 주성분의 입계 집중과 Hf의 우선 산확 억제되고, 삼각 형태의 내부 산화물이 plate형으로 변화되었다. MA6000의 경우 $AI_2O_3$ 주성분의 산화층이$Cr_2O_3$주성분의 외부 산화층과$AI_2O_3$ 주성분의 내부층으로 변화되었다. Ni base superalloys are composed of solid sohltion hardening elements(Co, Cr. Mo. W and so on) and $\gamma '$ precipitation hardening elements(A1, Ti, Nb, Ta and so on). To Improve the mechanical properties and oxidation resistanre of superalloys, rare earth elements(%r, Hf, Y and so on) are added to the inner substrate, or are used as coating materials. Their pffects on the growth rate and adhes~on of oxide are changed according to the kinds of oxides such as $AI_2O_3$ and $Cr_2O_3$. The effect of yttrium on the oxidation rate, grain size of oxide, internal structure, and crack resistance was investigated for two kinds of Ni-base superalloys. One in AF'115 superalloy containing Hf and the other is MA6000 superalloy containing $Y_2O_3$. They werr owid~zed at high temperature after yttrium surface modification using ion coater. Yttrium coating on the AF115 and MA6000 superalloys results in a marked change in the growth of the inner oxide. For AF115 superalloy, the degree of gram boundary segregation of $Cr_2O_3$, and prefer en^ tial oxidation of Hf are decreased, and the shape of inner oxidation layer was changed from triangle to plate type. For MA6000 superalloy, $Cr_2O_3$ oxide scale was transformed as outer oxidation layer of CrZOI and inner oxidation layer of $Cr_2O_3$.
최대규,설경원 전북대학교 공업기술연구소 1984 工學硏究 Vol.15 No.-
금속의 일방향 응고시 금속주형과 응고 금속내의 온도구배외 계면에서의 열저항의 존재유무에 따라 응고특성을 4가지 Model을 정하여 조사하였다. 계면에서의 열유동과 열전달계수등을 계산하고 이론적으로 응고시간, 응고두께 및 속도 등을 나타내는 수식을 유도하였다. 또한 과열된 용융금속을 금속주형에 주입할 때 응고시간에 미치는 영향을 사형의 경우와 비교하여 조사하였다.
微量의 Cu, Zr 을 添加한 Al-Zn-Mg 合金의 二段時效擧動에 關한 硏究
禹基道,薛景原 전북대학교 공업기술연구소 1985 工學硏究 Vol.16 No.-
Effect of two-step aging behavior was studied by means of hardness tester, differential thermal analysis(DTA) and transmission electron microscopy(TEM). The results obtained are as follows. 1. The increase of the number of GP zones and η′ phase with pre-aging time in isochronal pre-aging treatments shows almost no effects on the peak hardness after final aging treatments. 2. The effect of two-step aging treatments in final aging at 150℃, 170℃ after pre-aging at 70℃ is shown but that in final aging at 120℃ after pre-aging at 70℃ is not shown. 3. The age hardening effect by normal aging treatments at 170℃ is not shown but that by two-step aging treatments in final aging at 170℃ after pre-aging treatments at 70℃ is shown. 4. The increase of the number of GP zones and η′ phase with pre-aging temperature from 50℃ to 100℃ in isochronal pre-aging treatments shows almost no effects on the peak hardness after final aging treatments. 5. The peak hardness attained by two step aging treatments in final aging at 120℃, 130℃, 150℃ after preaging at 70℃ for 60min. is superior to that by two step aging treatments in final agint at 160℃, 170℃ after pre-aging at 70℃ for 60min.