• Transactions of Materials Processing
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• v.19 no.5
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• pp.283-289
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• 2010

Extrusion process in the bulk material for fabrication of miniature helical gears has problems such as a high forming load and short tool life because the cross-section is complex and asymmetry. To overcome these problems, in this study, miniature helical gears were fabricated by Zn-22Al powder hot extrusion. The included die angle for minimum extrusion load and improving die filling was determined by FE-simulation. The Zn-22Al spheroidal powder produced by gasatomization were compacted and sintered for extrusion experiment. The dimension of helical-gear is 0.3mm in module, 3.35mm in pitch diameter, $15^{\circ}$ in helix angle and the number of teeth is 12. All of the extrusion experiments were performed with internal helical gear die which was machined by precision electric discharge machining using the electrode. The experiment was conducted at $190^{\circ}C$ to $310^{\circ}C$ to obtain extrusive and mechanical properties. The extruded helical gears were analyzed through extrusion load, Vickers hardness and SEM images for each extrusion temperature. The powder hot extrusion process was successfully applied to fabricate a miniature helical gear.

• Journal of Powder Materials
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• v.17 no.1
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• pp.44-51
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• 2010

The rheological behavior of a cordierite honeycomb extrusion paste was investigated by measuring torque values in a Brabender plastograph. The extrusion pastes were formulated using binder (methy cellulose, MC), solvent (water), plasticizer (ploy ethylene glycol, PEG) and lubricants (oleic acid, OA). The mixing sequence and optimum organic binder, at least for homogeneous mixed state, can be determined from the rheological point of view. 3%MC-30%$H_2O$-1.5%PEG-1.0%OA with respect to the cordierite powder was chosen as a binder composition for the extrusion process of cordierite powder.

• Journal of Powder Materials
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• v.16 no.1
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• pp.50-55
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• 2009

Numerical simulations of the powder extrusion need an appropriate pressure-dependent constitutive model for densification modeling of the magnesium powders. The present research investigated the effect of representative powder yield function of the critical relative density model. We could obtain reasonable physical properties of pure magnesium powders using cold isostatic pressing. The proposed densification model was implemented into the finite element code. The finite element analysis was applied to simulation of powder extrusion of pure magnesium powder in order to investigate the densification and processing load at room temperature.

• Journal of Powder Materials
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• v.16 no.6
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• pp.438-441
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• 2009

Mg-Cu composites were successively fabricated using a combination of rapid solidification and extrusion processes. In addition, the microstructural variation of the composite was investigated by performing the extrusion repeatedly. It resulted that the composite formed an uniform and dense structure by the extrusion, and the microstructure became fine as the extrusion conducted repeatedly. The microstructural variation was known to be dependent on the number of extrusion and the area reduction ratio. The tensile strength was also measured as a function of the microstructural variation.

• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.427-431
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• 2006

Mg-4.3Zn-0.7Y (at%) alloy powders were prepared using an industrial scale gas atomizer, followed by warm extrusion. The powders were almost spherical in shape. The microstructure of atomized powders and those extruded bars was examined using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscope (EDS) and X-ray Diffractometer (XRD). The grain size of the powders was coarsen as the initial powder size increased. After the extrusion, the grain size became fine due to the severe plastic deformation during the extrusion with the ratio of 10:1. Both the ultimate strength and elongation were enhanced with the decrease of initial particle size.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.449-452
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• 2009

This paper was designed to fabricate the miniature spur gear with pitch circle of 1.8 by hot extrusion process of mechanically alloyed Zn-22wt%Al powder at various temperature. The mechanical alloying was preformed for ball milled times of 8h, 16h and 32h by the planetary ball milling. Mechanically alloyed powders were compacted cylindrical performs. Extrusions of the miniature spur gear using the alloyed powder were carried out at different extrusion temperatures. The extruded spur gear was sintered for 2h at $350^{\circ}C$ in argon atmosphere. The friction between the die and the powdered billet and the internally different density due to complex product shape cause the internal crack. To overcome the mentioned problems, high dimensional accuracy at cross section of the spur gear and uniform Vickers hardness could be obtained by graphite lubricant and controlling holding time.

• Transactions of Materials Processing
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• v.19 no.6
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• pp.352-356
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• 2010

This paper was designed to fabricate the micro-spur gear by the LIGA and hybrid powder extrusion process. It is important to manufacture a micro-die with a high aspect ratio and determine appropriate extrusion conditions for a microforming. Ni has been used to fabricate micro-dies. LIGA process was capable to produce micro-extrusion dies with close tolerance, longer bearing length and adequate surface quality. Superplastic Al-78Zn powders have the great advantage in achieving deformation under low stresses and exhibiting good micro-formability with average strain rate raging from $10^{-3}$ to $10^{-2} s^{-1}$ and constant temperature ranging from 503 to 563K. Al-78Zn powders were compacted into a cylindrical shape ($\Phi3\times$h10mm) under compressive force of 10kN and, subsequently, the compacted powders were extruded by the hybrid powder extrusion process controlling of the temperature holing time for a improvement on formability of Al-22Zn powder. Micro-extrusion has succeeded in forming micro-gear shafts.

• Food Science and Biotechnology
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• v.14 no.6
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• pp.758-765
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• 2005

Instant powders that only require mixing with water prior to consumption can be produced by extrusion for use in products such as instant beverages. Both extrusion processing conditions and particle size of powder are important to end-product characteristics. In this study, a twin-screw extruder was used under various processing conditions (feed moisture, barrel temperature, and screw speed) to produce extrudates from soft wheat flour, which were ground to powders with particle size ranges of less than 93, 93-145, and $145-249\;{\mu}m$. Effects of adding soy lecithin to wheat flour before extrusion were also investigated. Water absorption, solubility, suspension viscosity, and dispersibility of wheat powders were related to specific. mechanical energy measured during extrusion. Powder particle size was important to instant properties, especially ease of dispersal in water and stability to sedimentation. Addition of lecithin significantly improved dispersibility of powders.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.100-103
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• 1998

In this study, Al-Ni-Mm alloy has been produced by a gas atomization technique and consolidated by a powder extrusion method. The powders showed mixed structures of amorphous, fcc-Al phases and intermetallics. Each phase shows different size and quantity with different size of the powders due to the higher cooling rate of the finer powders. Because of the difference of the microstructure, the powders with the different size show differences of the mechanical properites of the powders and extrudates.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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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.