• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1000-1001
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• 2006

Two atomized alloy powders were pre-compacted by cold and subsequently hot forged at temperatures ranging from 653K to 845K. The addition of Cu and Mg causes a decrease in the eutectic reaction temperature of Al-10Si-5Fe-1Zr alloy from 841K to 786K and results in a decrease of flow stress at the given forging temperature. TEM observation revealed that in addition to Al-Fe based intermetallics, $Al_2Cu$ and $Al_2CuMg$ intermetallics appeared. The volume fraction of intermetallic dispersoids increased by the addition of Cu and Mg. Compressive strength of the present alloys was closely related to the volume fraction of intermetallic dispersoids.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1177-1178
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• 2006

Magnetic Properties of dust cores made of mixtures of atomized pure iron powder and pure alumina powder has been investigated in the temperature range from 673 to 1073K. The effect of annealing on coercivity has been positive effect up to 973K and thus coercivity is gradually reduced form 280A/m (as-compressed) to 160A/m (973K). However, dust cores annealed at 1073K displayed a 15% increasing of coercivity by annealing at 973K. Hysteresis loss shows a tendency similar to coercivity. Microstructure observation of specimens shows grain refinement by recrystallization in the temperature range from 773 to 1073K.

• Journal of Powder Materials
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• v.11 no.2
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• pp.97-104
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• 2004

In this paper processing and mechanical properties of Al-20 wt％ Si alloy was studied. A bulk form of Al-20Si alloy was prepared by gas atomizing powders having the powder size of 106-145 ${\mu}m$ and powder extrusion. The powder extrudate was subsequently equal channel angular pressed up to 8 passes in order to refine grain and Si particle. The microstructure of the gas atomized powders, powder extrudates and equal channel angular pressed samples were investigated using a scanning electron microscope and X-ray diffraction. The mechanical properties of the bulk sample were measured by compressive tests and a micro Victors hardness test. Equal channel angular pressing was found to be effective in matrix grain and Si particle refinement, which enhanced the strength and hardness of the Al-2OSi alloy without deteriorating ductility in the range of experimental strain of 30％.

• Journal of Powder Materials
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• v.24 no.2
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• pp.115-121
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• 2017

In this work, p-type Bi-Sb-Te alloys powders are prepared using gas atomization, a mass production powder preparation method involving rapid solidification. To study the effect of the sintering temperature on the microstructure and thermoelectric properties, gas-atomized powders are consolidated at different temperatures (623, 703, and 743 K) using spark plasma sintering. The crystal structures of the gas-atomized powders and sintered bulks are identified using an X-ray diffraction technique. Texture analysis by electron backscatter diffraction reveals that the grains are randomly oriented in the entire matrix, and no preferred orientation in any unique direction is observed. The hardness values decrease with increasing sintering temperature owing to a decrease in grain size. The conductivity increases gradually with increasing sintering temperature, whereas the Seebeck coefficient decreases owing to increases in the carrier mobility with grain size. The lowest thermal conductivity is obtained for the bulk sintered at a low temperature (603 K), mainly because of its fine-grained microstructure. A peak ZT of 1.06 is achieved for the sample sintered at 703 K owing to its moderate electrical conductivity and sustainable thermal conductivity.

• Journal of Powder Materials
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• v.18 no.5
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• pp.406-410
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• 2011

Green strength is an important property of powders since high green strength guarantees easy and safe handling before sintering. The green strength of a powder compact is related to mainly mechanical and surface characters, governed by interlocking of the particles. In this study, the effect of powder surface roughness on the green strength of iron powders was investigated using a transverse rupture test. Three-dimensional laser profiler was employed for quantitative analyses of the surface roughness. Two different surface conditions, i.e. surface roughness, of powders were compared. The powders having rough surfaces show higher green strength than the round surface powders since higher roughness leads increasing interlocked area between the contacting powders.

• Journal of Powder Materials
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• v.30 no.1
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• pp.41-46
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• 2023

In this study, an Al₈₂Ni₇Co₃Y₈ (at%) bulk metallic glass is fabricated using gas-atomized Al₈₂Ni₇Co₃Y₈ metallic glass powder and subsequent spark plasma sintering (SPS). The effect of powder size on the consolidation of bulk metallic glass is considered by dividing it into 5 ㎛ or less and 20-45 ㎛. The sintered Al₈₂Ni₇Co₃Y₈ bulk metallic glasses exhibit crystallization behavior and crystallization enthalpy similar to those of the Al₈₂Ni₇Co₃Y₈ powder with 5 ㎛ or less and it is confirmed that no crystallization occurred during the sintering process. From these results, we conclude that the Z-position-controlled spark plasma sintering process, using superplastic deformation by viscous flow in the supercooled liquid-phase region of amorphous powder, is an effective process for manufacturing bulk metallic glass.

• Journal of Powder Materials
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• v.15 no.4
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• pp.297-301
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• 2008

The Ni-based bulk metallic glass matrix composites were fabricated by spark plasma sintering of mixture of gas-atomized metallic glass powders and ductile brass powders. The successful consolidation of metallic glass matrix composite was achieved by strong bonding between metallic glass powders due to viscous flow deformation and lower stress of ductile brass powders in the supercooled liquid state during spark plasma sintering. The composite shows some macroscopic plasticity after yielding, which was obtained by introducing a ductile second brass phase in the Ni-based metallic glass matrix.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.933-934
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• 2006

The present study examines the sintering behaviour and effect of manganese addition both mechanically-blended and mechanically alloyed on Cr-Mo low alloyed steels to enhance the mechanical properties. Mn sublimation during sintering provides some specific phenomena which facilitate the sintering of alloying elements with high oxygen affinity. First step is the optimization of milling time to attain a master alloy with 50% of Mn which is diluted in Fe-1.5Cr-0.2Mo water atomized prealloyed powder by normal mixing. These mixtures are pressed to a green density of $7.1g/cm^3$ and sintered at $1120^{\circ}C$ in $90N_2-10H_2$ atmosphere.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.759-760
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• 2006

Ti-6Al-4V has low specific gravity, high corrosion resistance and superior mechanical properties but it is very difficult to control oxygen content in MIM process. It is necessary to use powders with coarse particle size to decrease oxygen content of powders, so feedstocks with poor fluidity and sintered bodies with lower density are obtained in such cases. Fine titanium hydride-dehydride powders were blended with atomized powders to accomplish higher fluidity and sintered density. Sintered bodies had higher sintered density and mechanical properties equivalent to those of wrought materials by controlling oxygen content less than 0.35mass%.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1035-1036
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• 2006

The microstructure and mechanical properties of the $Mg_{97}Zn_Y_2$ alloy prepared by spark plasma sintering of gas atomized powders have been investigated. After consolidation, precipitates were observed to form in the ${\alpha}-Mg$ solid solution matrix of the $Mg_{97}Zn_1Y_2$ alloy. These precipitates consisted of $Mg_{12}YZn$ and $Mg_{24}Y_5$ phases. The density of the consolidated bulk Mg-Zn-Y alloy was $1.86g/cm^3$. The ultimate tensile strength and elongation were dependent on the consolidation temperature, which were in the ranges of 280 to 293 MPa and 8.5 to 20.8 %, respectively.