• Korean Journal of Materials Research
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• v.11 no.12
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• pp.1020-1027
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• 2001

Powder type Ag system insert metals were manufactured by mechanical alloying method. Alloying method was the ball milling process using zirconia ball media, and all alloying variables were constant except the milling time. The milling times were selected 24, 48 and 72 hours. The insert metals made by milling method were observed using scanning electron microscope and x-ray analyses. And also, the evaluation of wettability and microstructures of the insert metals were conducted to investigate the characteristics of the brazed joint. The wettability of the insert metals made by milling of 48 hours, was the best condition. And the insert metals contained Cd shows good wettability, however, there was the oxides residue on the brazing test specimen. The microstructures of the manufactured and the commercial insert metals were almost same displaying the Cu- rich proeutectic and Ag-rich eutectic. Further, there were some porosities. The 48 hours alloyed insert metal was exhibited the most sound brazed joint without containing porosity due to the superior wettability and good alloying condition.

• Journal of Powder Materials
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• v.9 no.2
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• pp.110-115
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• 2002

In order to obtain the nano size $10wt%Cu-TiO_2$composite powders by mechanical alloying method for useful composite catalysis, the effects of mechanical alloying time on the formationof $10wt%Cu-TiO_2$ composite powders were analyzed. The phase transformation behaviors were experimented as the heat treating temperature increased. Homogeneous 10wt% Cu-rutile type $TiO_2$composite powders were synthesized in 40 hours by mechanical alloying. After 60 hours mechanical alloying 50 nm size $TiO_2$powders were obtained. Both the phase of mechanically alloyed 10 wt% $Cu-TiO_2$ and pure $TiO_2$ powders were not transformed to anatase after annealing at the temperature range between 350 to 500 $^{\circ}C$. The intermetallic compound of $Cu_2Ti_4$O was formed after 10 hours mechanical alloying, however it could be considered that this intemetallic phase dose not prevent the transformation of rutile $TiO_2$ to the anatase phase after heat treatment at the temperature between 350 and $550^{\circ}C$.

• Transactions of the Korean hydrogen and new energy society
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• v.16 no.4
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• pp.372-378
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• 2005

Ni/YSZ ($Y_2O_3$-stabilized $ZrO_2$) composite powder for a cathode material in high temperature electrolysis(HTE) was synthesized by a mechanical alloying method with Ni and YSZ powder. Microstructure of the composite and cell thickness for HTE reaction has been analyzed with various techniques of XRD, SEM to investigate effects of fabrication conditions. Employing the composite material, furthermore, the unit cell for HTE has been studied to evolve hydrogen from water. XRD patterns showed that the composites after wet mechanical alloying were composed of respective nano-sized crystalline Ni and YSZ. While ethanol as additive for mechanical alloying increased to $20\;{\mu}m$ of average particle size of the composites, alpha-terpineol effectively decreased to sub-micro size of that. This study has been found out the evolution of hydrogen by HTE reaction employing the fabricated cathode material, showing 1.4 ml/min of $H_2$ generation rate as increasing $20\;{\mu}m$ of cathode thickness.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.4
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• pp.194-203
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• 1993

Rapid solidified splats Al-(1, 3, 5Cr) Alloys were produced by atomization-splat quenching method. Effects of mechanical alloying on the structure and mechanical properties of rapidly solidified Al-(1, 3, 5)Cr alloys were studied. Degree of mechanical alloying of Al-(1, 3, 5)Cr alloys can be determined by observing the microstructural refinement, microhardness and microstructure of Al-(l, 3, 5)Cr splats during processing. In the initial stage of mechanical alloying of the Al-(1, 3, 5)Cr splats fracturing of the grain boundaries occured first, followed after fracturing of zone A regions. Saturation hardness of Al-(1, 3, 5)Cr alloys increased proportionally with increasing concentration of the solute (Cr). Age hardening was not observed in these alloys. Decomposition temperature of Al-1Cr splats after mechanical alloying was higher than that of Al-5Cr splats. The density of $Al_7$ Cr precipitates increased proportionally with increasing chromium content, as a result, there was a transition to finely and spherically dispersed phase after mechanical alloying.

• Journal of Powder Materials
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• v.8 no.2
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• pp.104-109
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• 2001

The semiconducting ${\beta}-FeSi_2$ compound has been recognized as a thermoelectric material with excel-lent oxidation resistance and stable characteristics at elevated temperature. In the present work, we applied mechanical alloying(MA) technique to produce ${\beta}-FeSi_2$ compound using a mixture of elemental iron and silicon powders. The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-K $\alpha$ radiation, thermal analysis and scanning electron microscopy. The single ${\beta}-FeSi_2$ phase has been obtained by mechanical alloying of $Fe_{33}Si_{67}$ mixture powders for 120 hrs or for 70 hrs coupled with the subsequent heat treatment up to $700^{\circ}C$. The grain size of ${\beta}-FeSi_2$ powders analyzed by Hall plot method was 44nm.

• Journal of Powder Materials
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• v.1 no.2
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• pp.167-173
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• 1994

Cu-10wt%W composite powders have been manufactured by a high energy ball milling technique. The composite powders were pressed at 250 MPa and sintered in a dry hydrogen at 103$0^{\circ}C$ for 4 hours. After sintering, Cu-10wt%W composite materials were forged. And the arc-resistance of forged materials which have the same relative density of 94% has been tested. Composite particles, i.e. tungsten particles distributed homogeneously in the copper matrix, was formed after 480 min mechanical alloying. Densities of these sintered materials were ranged from 74 to 84%. Densification degree was due to the formation of composite powders. As the mechanical alloying time increased, the hardness was increased and tungsten particle size was decreased. Arc loss of the forged specimens was decreased as increasing the mechanical alloying time.

• Journal of Integrative Natural Science
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• v.1 no.2
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• pp.84-88
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• 2008

The formation and thermal properties of the $BaO_2$ and $TiO_2$ mixtures were prepared by mechanical alloying method was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA). The rotating speed of 750 rpm shows more effects on the formation of $BaTiO_3$ single phase. The internal strain calculated using Williamson-Hall method was $4.27{\times}10^{-3}$ for the mixture milled for 300 min, the crystallite size was calculated using the Scherrer method decreased with milling time. The $BaTiO_3$ crystal improved crystallinity was formed by thermal annealing at a temperature of $600^{\circ}C$ for 1 h for the mixture milled for 300 min.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.246-252
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• 2011

The semiconducting $MnSi_{1.73}$ compound has been recognized as a thermoelectric material with excellent oxidation resistance and stable characteristics at elevated temperature. In the present work, we applied mechanical alloying (MA) technique to produce $MnSi_{1.73}$ compound using a mixture of elemental manganese and silicon powders. The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-$K{\alpha}$ radiation, thermal analysis and scanning electron microscopy. Due to the observed larger loss of Si relative to Mn during mechanical alloying of $MnSi_{1.73}$, the starting composition of a mixture Mn-Si was modified to $MnSi_{1.83}$ and then $MnSi_{1.88}$. The single $MnSi_{1.73}$ phase has been obtained by mechanical alloying of $MnSi_{1.88}$ mixture powders for 200 hours. It is also found that the grain size of $MnSi_{1.73}$ compound powders analyzed by Hall plot method is reduced to 40 nm after 200 hours of milling.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.151-152
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• 2006

Bi-Te thermoelectric powder was fabricated by mechanical alloying method for 1 to 10 hours under vacuum in planetary mill. We investigated the properties of mechanically alloyed Bi-Te powder by thermal analysis, X-ray diffractometer and FESEM with EDS Bi-Te raw material was formed to $Bi_2Te_3$ phase at condition over 3.5 hours of mechanical alloying time.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.34-41
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• 2004

A new method to fabricate the fine magnetic abrasives by using mechanical alloying is proposed. The mechanical alloying process is a solid powder process where the powder particles are subjected to high energetic impact by the balls in a vial. As the powder particles in the vial are continuously impacted by the balls, cold welding between particles and fracturing of the particles take place repeatedly during the ball milling process using a planetary mill. After the manufacturing process, fine magnetic abrasives which the guest abrasive particles c lung to the base metal matrix without bonding material can be obtained. The shape of the newly fabricated fine magnetic abrasives was investigated using SEM and its polishing performance was verified by experiment. It is very helpful to finishing the injection mold steel in final polishing stage. The areal ms surface roughness of the workpiece after several polishing processes has decreased to a few nanometer scales.