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순철박막의 증착속도, 미세구조 및 자성에 미치는 스퍼터링조건의 영향
한석희(Suk-Hee Han),김희중(Hi-Jung Kim),강일구(Il Koo Kang),최정옥(Jeong-Og Choi),이정중(Jung Joong Lee) 한국자기학회 1991 韓國磁氣學會誌 Vol.1 No.2
The influences of sputtering conditions on the deposition rate, the micro structure, and the magnetic properties have been studied in the pure iron thin films made by the RF magnetron sputtering. The deposition rate increases remarkably by applying the magnetic field on the substrate, and this effect is discussed with the increase of Ar ion.<br/> With increasing the input power the grain size and the lattice parameter are increased and the (110) plane is strongly developed. With Ar pressure the lattice parameter is decreased while the grain size is not changed.<br/> The smallest coercive force of 3 Oe is shown in the hard direction of Fe film sputtered at 60 W applying the magnetic field to the substrate. The coercive force is largely increased above 5mTorr due to the rough surface and the second phase. The Neel's theoretical relation between the film thickness and the coercive force can be applied to the sputtered Fe film with the thickness range of 50-200㎚.
Fe-C 계의 α/γ상평형에 필요한 열역학적 파라미터의 계산
강일구,임상호 대한금속재료학회(대한금속학회) 1992 대한금속·재료학회지 Vol.30 No.8
Parameters needed in model calculations of the α/γ phase equilibrium in Fe-C alloys are calculated by using new Monte Carlo procedures. The parameters include the carbon-carbon interaction energies and standard carbon potentials in the αand γ phases and the relative lattice stability of pure bcc and fcc Fe. Accurate values of the model parameters are determined by a comprehensive analysis of the existing experimental carbon activity data in both the αand γ phases and by utilizing the Fe-C phase diagram. The parameters determined in the present work together with the new Monte Carlo procedures will surely provide more confidence in the low temperature extrapolation of the metastable α/γ phase equilibrium.
강일구,김희중,증본건 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.5
Alloying effects on the crystallization temperature and the crystallization process of Fe-Cr-C-B alloys were studied by DSC and X-ray diffractometer. The crystallization temperature linearly increased with increasing the concentration of Cr and metalloids. The activation energy for crystallization was in the range of 83-97 ㎉/㏖, and its dependence to composition was similar to that of the crystallization temperature. Three crystallization processes of primary, eutectic and polymorphic were occurred with alloy composition. The final stable crystalline phases were α-(Fe, Cr) (bcc), (Fe, Cr)₃B(orthorhombic) and (Fe, Cr),B (tetragonal) in Fe_(47)Cr_(35)B_(18) alloy, (Fe, Cr)₃(C, B) (orthorhombic) in Fe_(41)Cr_(35)C_(12)B_(12) alloy, and α-(Fe, Cr)(bcc) and (Fe, Cr)₃ (C, B) (orthorhombic) in all Fe-Cr-C-B alloys except Fe_(41)Cr_(35)C_(12)B_(12) alloy.
Nb-Ta 합금에서 비정상적으로 높은 수소 고용도에 대한 열역학적인 해석
강일구,임상호 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.9
The abnormally high terminal solubility of hydrogen (TSH) in Nb-Ta alloys at 250 K was previously explained by Oates and Flanagan using the concept of para- (or pseudo-) equilibrium. In this paper, in order to provide a more accurate explanation for the low temperature TSH and furthermore the phase diagram of Nb-Ta-H system, we recalculate the TSH of Nb-Ta alloys by applying the same method used previously but considering more experimental thermodynamic results available. The present calculation is found to give a better agreement between the experimental and calculated TSH results. Also the phase diagram obtained from the present calculation is well in accord with the detailed structural information, whilst that from the previous calculation is not. The present work emphasizes the need to use accurate thermodynamic data in model calculations.
쾌삭황동 (快削黃銅) 의 절삭성 및 기계적 성질에 미치는 주조냉각속도의 영향
강일구,유연철 대한금속재료학회(대한금속학회) 1976 대한금속·재료학회지 Vol.14 No.5
鑄造冷却速度가 快削黃銅의 切削性 및 機械的性質에 미치는 영향을 砂型 金型 및 冷却水 통한 金型을 使用하여 硏究하였다. 冷却速度가 빠를때는 납粒子는 素地金屬內에 微細하게 分布되었으며 β相은 針狀형태를 나타내었다, 冷却速度가 늦을 경우는 납은 둥글고 크게 분포되고 粒界에 몰리는 경향을 나타냈으며 β相은 板狀형태를 보였다. 切削性 및機械的性質은 鑄造冷却速度가 빨라서 납粒子 및 β相이 微細하고 針狀일 경우에 우수하였다. The effects of cooling rate on the machinability and other mechanical properties of free cutting brass were examined through sand mold, metal mold and water-cooled metal mold casting respectively. When the cooling rate was rapid, the lead particles were finely dispersed throughout the matrix and the β-phases appeared to be needlelike, when the cooling rate was slow, the lead particles formed themselves into large spheroids mainly along the grain boundaries while the β-phases shaped into plates. The machinability and mechanical properties turned out satisfactory in the case of rapid cooling rate.
금속-금속계 Fe-Co-Zr (Hf) 비정질합금의 2단엔탈피완화현상
노태환,강일구 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.4
The enthalpy relaxation phenomenon for metal-metal type Fe-Co-Zr(Hf) amorphous alloys has been studied calorimetrically. The magnitude of the exothermic reaction resulted from the irreversible enthalpy relaxation in amorphous (Fe_(1-x)Co_x)_(90) Zr_(10) (x=0-1) alloys was the largest at x=0.5 The changes in ΔC_p(exo) with temperature for amorphous (Fe_(0.5)Co_(0.5))_(90)Zr_(10) and (Fe_(0.5)Co_(0.5))_(90) Hf_(10) alloys showed two stages, a low-temperature one which shows a peak at about 525K and a high-temperature one which shows a peak near Tx. The low-temperature reaction was ascribed to the rearrangement between Fe and Co atoms with weak bonding nature and the high-temperature one to the rearrangement between Fe, Co and Zr, Hf atoms with strong bonding nature. And it was noticed that the high-temperature relaxation causes the decrease in Curie temperature for amorphous Fe-Co-Zr alloys.
이동녕,강일구,유연철 대한금속재료학회(대한금속학회) 1980 대한금속·재료학회지 Vol.18 No.5
철-42% 니켈 합금봉에 열간드로잉으로 구리를 피복접착시켜 구리층의 비율이 18-28%(중량)인 복합봉 내지 선재를 만드는 과정을 드로잉에 중점을 두고 연구하였다. 드로잉은 철-니켈 합금봉에 구리관을 씌워 드로잉하여 합금봉과 구리관 사이의 간격을 줄이는 예비드로잉, 예비드로잉한 것을 심봉과 구리층 사이의 결합을 얻기 위한 열간드로잉, 열간드로잉으로 얻어진 복합봉을 원하는 치수에까지 냉간드로잉하는 것으로 되어있다. 예비드로잉은 심봉과 관의 치수 단면수축률에 따라 관싱킹이나 이동 맨드릴에 의한 관드로잉으로 취급 될 수 있었고 열간드로잉에서는 다이각과 틈새가 중요한 인자였으며 냉간드로잉 제품의 경도분포로 열간드로잉에서의 이러한 인자를 이해하는데 도움이 되었다. Fabrication of copper clad iron-42% nickel alloy rods or wires (copper ratio : 18-28%) by hot drawing has bean studied laying emphasis on various drawing processes. The processes are composed of predrawing for reduction of clearance between a core rod and a copper tubing, hot drawing for bonding between the core and the copper layer of the predrawn rod, and cold drawing of the composite rod to a predetermined size. The predrawing process was taken for tube sinking or tube drawing with a moving mandrel depending on dimensions of core and tubing and reduction in area. The important factors in hot drawing were the drawing die angle and the clearance between core and tubing. These could be understood by measuring the hardness distribution in cold drawn composite rods.