• 열처리공학회지
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• 제19권3호
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• pp.149-155
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• 2006

The effects of eight types of spheroidizing annealing conditions including annealing temperature, annealing time, cooling rate, and gas atmosphere in the annealing furnace on the microstructure were determined in SM45C steel which has been widely used for automotive parts. The well-developed spheroidized structure and minimum hardness were obtained when the steel was heat-treated 6 hours at $740^{\circ}C$, cooled to $710^{\circ}C$ at a cooling rate of $24^{\circ}C/h$, and then kept for 7 hours at the $710^{\circ}C$ followed by air cooling. In order to increase the productivity and to save the manufacturing cost, it is desirable to apply a faster cooling rate in the spheroidizing annealing. It was found that air cooling was the fastest cooling rate applicable to the SM45C steel. The steel heat treated in air showed the decarburized layer of about $110{\mu}m$ in thickness at the surface of the specimen, resulting in serious problems in the quality of the quenched product.

• 열처리공학회지
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• 제19권5호
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• pp.270-279
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• 2006

The effects of eight types of spheroidizing annealing conditions including annealing temperature, annealing time, cooling rate, and furnace atmosphere on the microstructure and hardeness were determined in SCM440 steel which has been widely used for automotive parts. The well-spheroidized structure and minimum hardness were obtained when the steel was heat-treated at $770^{\circ}C$ for 6 hours, cooled to $720^{\circ}C$ at a cooling rate of $24^{\circ}C/h$, and then kept for 7 hours at the $720^{\circ}C$ followed by air cooling. In order to increase the productivity and to save the manufacturing cost, it is desirable to apply a faster cooling rate to the spheroidizing annealing. It was found that a cooling rate of $100^{\circ}C/hr$ was the fastest cooling rate applicable to the SCM440 steel among the four cooling rates used in this study. The microstructure consisted of ferrite and very fine spheroidized cementite when the steel was annealed for 13 hours at $720^{\circ}C$ below $A_{C1}$ temperature. This was caused by the short annealing time and the retarding effect of Cr and Mo on both the dissolution of pearlite to cementite and coarsening of spheroidized cementite. The steel heat treated in air showed the decarburized layer of about $125{\mu}m$ in thickness at the surface.

• 열처리공학회지
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• 제10권4호
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• pp.246-254
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• 1997

The 6.5wt %Si-Fe alloy sheets were made by the twin roll process. The magnetic properties and microstructures of sheets annealed in the sulfur atmosphere were studied. In the as-prepared sheet, non-oriented columnar grains about $10{\mu}m$ in diameter were observed, which grew from the surface to the inner part of the sheet. When the annealing temperature was around $700^{\circ}C$, the primary recrystallization was formed around the middle part of the sheet thickness, and the grain size increased with increasing annealing temperature. At the annealing temperature of $900^{\circ}C$, the grain size became $30{\sim}40{\mu}m$. Around the annealing temperature, the motive force of the grain growth is the grain boundary energy. However, above $1000^{\circ}C$ the surface energy played an important role in the observed grain growth. When the sheet were annealed at $1200^{\circ}C$, the grains whose (100) planes were paralled to the thin plate surface grew, and all sheet surfaces were covered with these grains after 1 hour annealing. This phenomenon is called tertiary recrystallization. A difference in surface energy between (100) and (110) surfaces provides a driving force for growth of tertiary grains. The coercive force was 0.27 mOe and the AC core loss $W_{12/50}$ was 0.38w/kg for the 6.5wt%Si-Fe alloy.

• 한국분말재료학회지
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• 제10권4호
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• pp.235-240
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• 2003

The $Al/Al_2O_3$ composites fabricated by powder in sheath rolling method were cold-rolled by 50% reduction and annealed for 1.8 ks at various temperatures ranging from 200 to 50$0^{\circ}C$, for improvement of the mechanical properties. The mechanical properties and texture of the composites after rolling and annealing were investigated. The tensile strength of the composites increased significantly due to work hardening after cold rolling, however it decreased due to restoration after annealing. The strength of the composites was improved by thermo mechanical treatment. On the other hand, the texture evolution with annealing temperatures wa,i different between the unreinforced material and the composites. The unreinforced material showed a deformation (rolling) texture of which main component is ｛112｝<111> at annealing temperatures up to 30$0^{\circ}C$. However, the composites have already exhibited a recrystallization texture of which main component is ｛001｝<100> after annealing at 20$0^{\circ}C$. This proves that the critical temperature for recrystailization is lower in the composites than in the unreinforced ones.

• 한국재료학회지
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• 제18권9호
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• pp.486-491
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• 2008

The effect of annealing treatment conditions on the interfacial adhesion energy between electrolessplated Ni film and polyimide substrate was evaluated using a $180^{\circ}$ peel test. Measured peel strength values are $26.9{\pm}0.8,\;22.4{\pm}0.8,\;21.9{\pm}1.5,\;23.1{\pm}1.3,\;16.1{\pm}2.0\;and\;14.3{\pm}1.3g/mm$ for annealing treatment times during 0, 1, 3, 5, 10, and 20 hours, respectively, at $200^{\circ}C$ in ambient environment. XPS and AES analysis results on peeled surfaces clearly reveal that the peeling occurs cohesively inside polyimide. This implies a degradation of polyimide structure due to oxygen diffusion through interface between Ni and polyimide, which is also closely related to the decrease in the interfacial adhesion energy due to thermal treatment in ambient conditions.

• Composites Research
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• 제18권2호
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• pp.38-45
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• 2005

본 연구에서는 시차주사열량분석장치와 X-선 회절장치를 이용하여 어닐링 열처리 조건에 따른 니티놀 형상기억합금의 상변환 특성과 결정구조를 조사하였다. 어닐링 열처리 조건으로는 열처리 시간과 열처리 온도를 고려하였으며 특히 열처리 시간은 5분. 15분, 30분, 45분 그리고 열처리 온도는 $400^{\circ}C,\;500^{\circ}C,\;525^{\circ}C,\;550^{\circ}C,\;575^{\circ}C,\;600^{\circ}C,\;700^{\circ}C,\;800^{\circ}C,\;and\;900^{\circ}C$를 적용하였다 연구결과에 따르면 열처리 시간과 열처리 온도 등의 어닐링 열처리 조건은 니티놀 형상기억합금의 상변환 특성과 결정구조에 큰 영향을 미침을 알 수 있었다.

• Journal of Magnetics
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• 제15권4호
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• pp.179-184
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• 2010

We have investigated the effects of post annealing on iron oxide nanoparticles synthesized by the novel hydrothermal synthesis method with the $FeSO_4{\cdot}7H_2O$. To investigate the post annealing effect, the as-synthesized iron oxide nanoparticles were annealed at different temperatures in a vacuum chamber. The morphological, structural and magnetic properties of the iron oxide nanoparticles were investigated with high resolution X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Mossbauer spectroscopy, and vibrating sample magnetometer analysis. According to the XRD and HRTEM analysis results, as-synthesized iron oxide nanoparticles were only magnetite ($Fe_3O_4$) phase with face-centered cubic structure but post annealed iron oxide nanoparticles at $700^{\circ}C$ were mainly magnetite phase with trivial maghemite ($\gamma-Fe_2O_3$) phase which was induced in the post annealing treatment. The crystallinity of the iron oxide nanoparticles is enhanced by the post annealing treatment. The particle size of the as-synthesized iron oxide nanoparticles was about 5 nm and the particle shape was almost spherical. But the particle size of the post annealed iron oxide nanoparticles at $700^{\circ}C$ was around 25 nm and the particle shape was spherical and irregular. The as-synthesized iron oxide nanoparticles showed superparamagnetic behavior, but post annealed iron oxide nanoparticles at $700^{\circ}C$ did not show superparamagnetic behavior due to the increase of particle size by post annealing treatment. The saturation of magnetization of the as-synthesized nanoparticles, post annealed nanoparticles at $500^{\circ}C$, and post annealed nanoparticles at $700^{\circ}C$ was found to be 3.7 emu/g, 6.1 emu/g, and 7.5 emu/g, respectively. The much smaller saturation magnetization value than one of bulk magnetite can be attributed to spin disorder and/or spin canting, spin pinning at the nanoparticle surface.

• Tribology and Lubricants
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• 제37권2호
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• pp.62-70
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• 2021

The problem with intermetallics coating using the heat of molten casting is that the heat generated during combustion synthesis dissolves the coating and the substrate metal. This study investigates whether pre-annealing before synthesis can control the reaction heat, with the aim of Ni₃Al coating on the casting surface. Therefore, the effects of the annealing temperature and time on the combustion synthesis behavior of the powder compact of Ni-25at%Al after annealing were investigated. As results, the reaction heat when synthesized decreased as the annealing temperature was high and the annealing time was longer. This was attributed to the fact that Al was diffused to Ni particles during low temperature annealing and intermediate Ni-Al compounds were formed during high temperature annealing. After combustion synthesis, however, it was found that their microstructures were almost identical except for the amount of intermediate intermetallics. Furthermore, an annealing temperature above 450℃, at which intermediate compounds begin to form, is needed to prevent the dissolving problem during synthesizing. The intermetallics synthesized after annealing at higher temperature and prolonger annealing time showed a good wear resistance. This might be because much intermediate intermetallics of high hardness were remained in the microstructure.

• 전자공학회논문지A
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• 제30A권7호
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• pp.47-59
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• 1993

16M DRAM 용 Al/Si contact 의 열적안정성을 개선하기 위하여 "stuffed" TiN/Ti diffusion barrier를 사용하였다. Diffusion barrier 로서의 특성을 개선하기 위한 Al 증착전 TiN/Ti barrier metal의 열처리 과정중 barrier metal의 두께, 열처리온도, 분위기 등을 변화시켰다. 질소분위기하에서 450도에서 TiN(900A)/Ti(300A) 박막을 열처리 하여 "stuffed" barrier metal을 형성 시켰을 경우 Al 원자의 TiN층으로의 확산의 600도에서 후속열처리한 경우 일어났으나, 700도까지도 Al-spike를 관찰할 수 없었다. 그러나 "stuffed" barrier metal을 550도에서 형성한 경우에는 600도의 후속열처리온도에서 Al이 Si 기판으로 침투했음을 관찰하였다. 박막의 두께를 얇게한 경우, 600도의 후속 열처리에서 Al-spike가 형성되었음을 확인하였다.

• 열처리공학회지
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• 제19권4호
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• pp.208-218
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• 2006

The effects of the grain size on the magnetic properties in extra-low carbon steel after strain annealing were investigated. Two kinds of sample were prepared. One is the annealed sheet, which was annealed at $670^{\circ}C$ and $850^{\circ}C$ for various time periods after cold rolling. The other is the strain annealed sheet, which was temper rolled by 0.4% and subsequently strain annealed at the temperature ranging between $670^{\circ}C$ and $850^{\circ}C$ for various time periods. The grains after strain annealing became more coarse than those after primary annealing. The grains were coarsened due to the strain induced grain boundary migration (SIGM). It was found that the permeability tended to be increased and coercivity tended to be decreased with the increase of grain size. The optimum magnetic properties was achieved after strain annealing at $850^{\circ}C$ for 30 minites. Under this condition, the coercivity was measured to be 0.6 and the permeability was measured up to be 13000.