• Journal of Powder Materials
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• v.19 no.3
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• pp.226-231
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• 2012

In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 ${\mu}m$ at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.

• Journal of Powder Materials
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• v.26 no.2
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• pp.101-106
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• 2019

Ni-based oxide dispersion strengthened (ODS) alloys have a higher usable temperature and better high-temperature mechanical properties than conventional superalloys. They are therefore being explored for applications in various fields such as those of aerospace and gas turbines. In general, ODS alloys are manufactured from alloy powders by mechanical alloying of element powders. However, our research team produces alloy powders in which the $Ni_5Y$ intermetallic phase is formed by an atomizing process. In this study, mechanical alloying was performed using a planetary mill to analyze the milling behavior of Ni-based oxide dispersions strengthened alloy powder in which the $Ni_5Y$ is the intermetallic phase. As the milling time increased, the $Ni_5Y$ intermetallic phase was refined. These results are confirmed by SEM and EPMA analysis on microstructure. In addition, it is confirmed that as the milling increased, the mechanical properties of Ni-based ODS alloy powder improve due to grain refinement by plastic deformation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.463-467
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• 1998

The microstructure evolution during mechanical alloying (MA) of Nb and Sn powder; of average composition $Nb_3Sn$, has been investigated by X-ray diffraction (XRD). The structural development with milling time depends on the ball size for a given powder/ball ratio. Using a larger ball of 9.5 mm diameter, the elemental powders initially alloy mechanically to form an A15 structure phase, and then amorphized with continued milling. However, in case of milling with a smaller ball of 3.968 mm diameter, an amorphous phase is first formed. These results can be understood by considering the dependence of the milling energy on the ball size. The homogeneous stoichiometric $Nb_3Sn$ phase could be easily obtained by heat treatment of supersaturated solid solution produced by MA. Heat treatment of an amorphous formed by MA resulted in the mixture of the $Nb_3Sn$ and $Nb_6Sn_5$phases.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.3
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• pp.1067-1082
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• 1991

본 연구에서는 비교적 강성이 약한 볼 엔드밀 공구에 있어서 처짐으로 인한 그 가공 특성을 알기 위하여, 변화된 칩 두께 및 처짐 모델로부터 절삭력을 예측하며 또한 절삭력에 의한 공구의 처짐으로 인하여 공구의 플랭크 부위와 공작물간의 발생하 는 간섭 특성을 고찰하고, 이러한 특성이 절삭성과 가공 오차에 미치는 영향을 실험을 통하여 분석하여 본다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.84-84
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• 2003

The effects of Ti addition on microstructure and mechanical properties of (Al+Xat.%Ti)2at%B (X=0.5, 1, 2) fabricated by mechanical alloying and spark plasma sintering (SPS) were investigated. These alloys were prepared by high energy ball milling (attritor) and then fracture toughness was investigated by using a charpy impact tester. The SPS method was used to consolidate (Al+Xat.%Ti)fat.%B with the pressure of 50MPa. The powders were successfully consolidated to alloy which the theoretical density is 99%. It was confirmed that the fracture toughness of Al-Bat.% matrix composites was increased by the addition of Ti.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1888-1896
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• 2002

This study presents a new type of CNC interpolator that is capable of generating cutter paths for ball-end milling of NURBS surfaces. The proposed surface interpolator comprises real-time algorithms for cutter contact (CC) path scheduling and CC path interpolator. Especially in this study, a new interpolator module to regulate cutting forces is developed. This propose algorithm utilizes variable-feedrate commands along the CC path according to the curvature of machined surfaces during the interpolation process. Additionally, it proposes an OpenGL graphic library for computer graphics and animation of interpolated tool-position display. The proposed interpolator is evaluated and compared with the existing method based on constant feedrates through computer simulations.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.134-135
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• 2005

The responses of nanocrystalline aluminum powder of different grain sizes, prepared by ball milling and consolidated into bulk specimens by hot pressing, were determined under quasi-static and dynamic compression. The experiments demonstrated that the reduction in grain size resulted in several-fold increase in hardness and strength; the responses of nanocrystalline aluminum was found to be strain-rate dependent.

• Journal of Powder Materials
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• v.7 no.1
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• pp.27-34
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• 2000

The fabrication process and mechanical properties of SiC particle prefrrms with high volume fraction ranged 50∼71% were investigated to make metal matrix composites for possible applications as heat sinks in electronic packares. The SiC particle preforms with 50∼71vol% of reinforcement were fabricated by a new modified process named ball milling and pressing method. The SiC particle performs were fabricated by ball milling of SiC particles with single sized of 48${\mu}$m in diameter or two different size of 8${\mu}$m and 48${\mu}$min diameter, with collodal SiO2 as inorgnic binder in distilled water, and the mixed slurries were cold pressed for consolidation into final prefom. The compressive strengths og calcined SiC particle prefoms increased from 20MPa to 155MPa with increasing the content of inorganis binder, temperature and time for calcination. The increase of compressive strength of SiC particle bridge the interfaces of two neighboring SiC particles.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.824-825
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• 2006

Homogeneous microstructures of the PM compacts are difficult to attain when mixed elemental powders are used. This study examined the microstructures of pressed-and-sintered and MIM products that contain Ni and Mo.Ni-rich areas, which were lean in carbon and were soft and were found easily in regular specimens. Gaps or cracks near the Ni-rich or Mo-rich areas were also frequently observed. This problem worsened when Ni and Mo particles were large and were irregular in shape. By using ball milling treatment and ferroalloy powders, the microstructure homogeneity and mechanical properties were improved. The addition of 0.5wt%Cr further improved the distribution of Ni because Cr reduced the repulsion effect between nickel and carbon. With the elimination of Ni-rich areas, more bainites and martensites were formed and mechanical properties were significantly improved.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.3
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• pp.468-484
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• 1992

본 연구에서는 기존의 유연 볼 엔드밀의 절삭력 모델을 바탕으로 자유 곡면의 정삭 가공에서 발생할 수 있는 과대 또는 과소 절삭을 방지하면서 그 가공의 효율성을 높이기 위한 볼 엔드밀의 이송 속도 결정법을 제시하고자 한다. 먼저, 자유 곡면의 가공에서 발생될 수 있는 공구의 처짐에 따른 가공오차에 대하여 볼 엔드밀 공구의 처 짐벡터와 공작물의 공구 접촉점에서의 법선벡터로 표현되는 가공오차(machining error ) 예측 모델식을 유도하였다. 본 가공오차 예측 모델식은 다시 절삭날당 가지는 이 송량의 함수로 전개되어 그 곡면의 주어진 가공 공차(machining tolerance)를 만족시 키는 이송속도를 결정하게 된다.