• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1296-1297
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• 2006

Both plastic and elastic properties change dramatically from the beginning to the end of the compaction phase. Previous investigations have shown that powder transfer and high powder flow during initial compaction at low density affects the strength of the final component significantly. Investigated here are shear failure and elastic shear modulus in the low density range for hard metal powder and for pre-alloyed water atomized iron powder. Direct shear test equipment for sand and clay has been modified to measure the shearing properties of powder for an axial loading between 1 kPa and 500 kPa.

• 한국분말재료학회지
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• 제10권1호
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• pp.26-33
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• 2003

Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders rapidly solidified by the gas atomization method were subjected to mechanical milling(MM). The morphology, microstructure and hardness of the powders were investigated as a function of milling time using scanning electron microscopy(SEM), transmission electron microscopy(TEM) and Vickers microhardness tester. Microstructural evolution in gas-atomized Al-l4wt.%Ni-l4wt.% Mm(Mm=misch metal) alloy powders was studied during mechanical milling. It was noted that the as-solidified particle size of $200\mutextrm{m}$ decreases during the first 48 hours and then increases up to 72 hours of milling due to cold bonding and subsequently there was continuous refinement to $20\mutextrm{m}$ on milling to 200 hours. Two microstructurally different zones, Zone A, which is fine microstructure area and Zone B, which has the structure of the as-solidified powder, were observed. The average thickness of the Zone A layer increased from about 10 to $15\mutextrm{m}$ in the powder milled for 24 hours. Increasing the milling time to 72 hours resulted in the formation of a thicker and more uniform Zone A layer, whose thickness increased to about $30~50\mutextrm{m}$. The TEM micrograph of ball milled powder for 200 hours shows formation of nano-particles, less than 20 nm in size, embedded in an Al matrix.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.227-228
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• 2006

Powder injection molding (PIM) is a suitable technology for the fabrication of complex shape titanium and its alloys, and has a great potential in many applications. This paper dealt with the injection molding of hydride dehydrogenization (HDH) titanium powder, spheroidized HDH titanium powder and gas atomized titanium powder. Rheological and thermalgravimetric behaviors were compared between the feedstocks of the three powders, and a tentative application of Ti PIM to eye frame temple and bridge was briefed.

• 한국주조공학회지
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• 제41권3호
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• pp.235-240
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• 2021

진공 가스분사법으로 제조된 Fe₇₅B₁₃P₅Nb₂Hf₁C₄ 합금의 응고중 액상의 크기와 이에 따른 냉각속도의 변화가 정출상의 형성에 미치는 영향에 대한 고찰을 하였다. 고온 액상에서 동일한 조건으로 응고된 서로 다른 크기의 액상이 구형의 분말형태로 응고될 때 크기에 따른 임계냉각속도의 차이를 계산하였으며, 액상의 평균 반지름이 3배정도 크기 차이가 날 경우 고상으로 변태할 때 임계냉각속도가 13.5배까지 차이가 나는 것을 알 수 있었다. 이러한 임계냉각 속도의 차이에 따른 정출상의 형성과 정출상의 형태와 크기에 따른 탄화물의 형성 거동을 조사하여 열역학 계산으로 예측된 결과와 비교 분석하였으며, 분말입자의 크기가 20~45 마이크론일 경우 Hf과 Nb이 포함된 MC타입의 탄화물이 초정으로 형성 되는 것을 알 수 있었으며 이때 Hf과 Nb의 비율은 합금의 조성 및 냉각속도에 따라 변화됨을 관찰 할 수 있었다.

• 한국분말재료학회지
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• 제5권2호
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• pp.111-121
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• 1998

Thick and dense deposit of higher than 97% of theoretical density was formed by induction plasma spraying. To investigate the effects of powder morphology on the density of deposit, two different kinds of Yttria-Stabilized-Zirconia powder, METCO202NS (atomized & agglomerated) and AMDRY146 (fused & crushed), were used and compared. After plasma treatment, porous METCO202NS powder was all the more densely deposited and its density was increased. In addition to the effect of powder morphology, the process parameters such as, sheath gas composition, probe position, particle size and spraying distance, and so on, were evaluated. The result of experiment with AMDRY146 powder, particle size and spraying distance affected highly on the density of the deposit. The optimum process condition for the deposition of -75 ${\mu}m$ of 20%-Yttria-Stabilized-Zirconia powder was 120/201/min of Ar/$H_2$ gas rate, 80 kW of plasma plate power, 8 cm of probe position and 150 Torr of spraying chamber pressure, at which its density showed 97.91% of theoretical density and its deposition rate was 20 mm/min. All the results were assessed by statistical approach what is called ANOVA.

• 한국분말재료학회지
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• 제1권1호
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• pp.66-71
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• 1994

Optical microstructures and mechanical properties of Na gas atomized Al-20Si-5Fe alloying powder and its hot extrudates were studied on 3 different types of powder size distribution. This powder showed the size distribution of 10~210 $\mu\textrm{m}$. Also the microstructures of $\alpha$-Al, primary and eutectic Si and needle shaped intermetallic compounds were observed by optical microscope. These needle shaped intermetallic compounds were identified as ${\delta}Al_4FeSi_2$- by XRD and EDX analysis. The ultimate tensile strength(UTS) of these alloy extrudates was increased from 324 to 390 MPa with decreasing powder size range from 120~210 $\mu\textrm{m}$ to 10~64 $\mu\textrm{m}$. A value of Micro-vic-kers hardness was simillar to the result of UTS. These extrudates showed better wear resistance than those of Al-20Si-2X(X : Ni, Cr, Zr), although they are insensitive to the size distribution. These results indicate that the presentation of ${\delta}Al_4FeSi_2$ intermetallic compounds contributed to the wear resistance improvement.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.733-734
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• 2006

Granulated powders, prepared from PF-5F($D_{50}=4(\mu}m$), PF-10F($D_{50}=6{\mu}m$) and PF-20F($D_{50}=10{\mu}m$) water atomized powder, were compacted, debound and sintered to evaluate the properties of sintered parts. As a result, the relative sintered density of about 97% at sintering temperature of 1423K was obtained. It can be considered that by using granulated finer particle size powder, mechanical properties of sintered parts were also improved.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1266-1267
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• 2006

[ $MgZn_{4.3}Y_{0.7}$ ] alloy powders were prepared using an industrial scale gas atomizer, followed by warm extrusion. The powders were almost spherical in shape. The microstructure of powders as atomized and bars as extruded was examined as a function of initial powder size distribution using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscope (EDS) and X-ray Diffractometer (XRD). The grain sizes were decreased with extruding as well as decreasing the initial powder sizes. Both the ultimate strength and elongation were enhanced as the initial powder sizes were decreased.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.568-569
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• 2006

The use of the nickel free, high nitrogen stainless steel powder and nitriding during sintering of iron based materials have been shown as an alternative way to the conventional PM stainless steels containing nickel. Nitrogen as an alloying element for iron improves in an effective way the properties of sintered alloyed steels. The powder metallurgy route is a suitable way to introduce nitrogen into these alloys and, in particular, to produce high nitrogen (close to the solubility limit) stainless steels. The paper presents and discusses the nitriding behavior of nickel-free stainless steels produced by powder metallurgy method. Alloyed melt was atomized by nitrogen and in this way nitrogen was introduced into the powder. Further nitriding occurred during sintering in a nitrogen atmosphere. For comparison, compacts having the same composition as an alloyed powder were produced from elemental powders mixture. Sintering-nitriding behaviour of investigated materials has been controlled by dilatometry, chemical and X-Ray phase analysis and metallography. Mechanical properties of sintered compacts were also measured.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2004년도 International Symposium on Powder Materials and Processing
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• pp.100-101
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• 2004