Journal of Powder Materials

[Korean]
Manufacture of Metal Foams and Porous Metal, and Their Application: J Korean Powder Metall Inst. 2001;8(4):215-222.

[Korean]
The Synthesis of Ti-37.5at%Si Powders by MA and Their Sintering Characteristics: J Korean Powder Metall Inst. 2001;8(4):223-230.

Abstract PDF: Ti-37.5at%Si elemental powder mixtures were mechanically alloyed by a high-energy ball mill, followed by CIP (cold isostatic pressing) and HIP (hot isostatic pressing) for different processing conditions. Only elemental phases (Ti and Si) were observed for the 5 min mechanically alloyed (MA 5 min) powder, but only Ti_5Si_3phase was observed for the 30 min mechanically alloyed (MA 30 min) powder. Ti_5Si_3phase was observed for the HIPed compact of MA 5 min and 30 min powders at 150 and 190 MPa for 3 hr at 1000°C. For the HIPed compacts, the highest sintered density was obtained to be 99.5% of theoretical density by a HIP step at 1350°C at 190MPa for 3hr. The hardness values of the HIPed Ti_5Si_3compacts at 1350°C at 150/190 MPa for 3hr were higher than HRC 76. The densification and mechanical property of HIPed Ti_5Si_3compacts was found to depend on more HIP temperature than HIP pressure.

[Korean]
One Step Synthesis of Dense WC-20 vol.% Co Super Hard Material: J Korean Powder Metall Inst. 2001;8(4):231-238.

Abstract PDF: We combined Field-Activated Combustion Synthesis(FACS) with mechanical pressure to produce dense WC-20 vol.%Co composite in one step. The hardness, the fracture toughness and the relative density of the dense WC-20 vol.%Co were investigated. Under the application of 60 MPa pressure and 3000A current on the reactants, the relative density of WC-20 vol.%Co composite was 99.4%. The fracture toughness and hardness were 9.4 MPa.m1/2 and 1672kgtextrmmm2 respectively. The fracture toughness and hardness of WC-20 vol.%Co composite produced by FAPACS were lower than that of nanostructured composite, but similar to commercial ones. Therefore we concluded that the FAPACS method which can produce WC-20 vol.%Co within several minutes in one step is superior to conventional ones.

[Korean]
Selective Laser Sintering of Cu/Polyamide Mixed Powder: J Korean Powder Metall Inst. 2001;8(4):239-244.

Abstract PDF: To investigate the effect of process parameters on selective laser sintering of Cu/polyamide mixed powder, Cu/polyamide mixed powder was sintered by selective laser with changing laser power and scanning speed. The properties of sintered body were evaluated by measuring the density and tensile strength, and analysis of XRD, FT-Raman and microstructure. With an increase in the laser power, the density and ultimate tensile strength of sintered Cu/polyamide body increase and then decrease. The maximum values of the density and ultimate tensile strength were decreased with increasing laser scanning speed. These changes were concerned with the difference of irradiation energy of laser into the powder layer. It was considered that the change of the mechanical property of the sintered body with irradiation energy of laser is due to the changes of amount of copper particle and property of polyamide.

[Korean]
Fabrication of W-10wt.%Cu Powder for the Application of Metal Injection Molding: J Korean Powder Metall Inst. 2001;8(4):245-252.

Abstract PDF: Recent remarkable progress in the semiconductor industry has promoted smaller size of semiconductor chips and increased amounts of heat generation. So, the demand for a substrate material to meet both the characteristics of thermal expansion coefficient and heat radiation has been on the increase. Under such conditions, tungsten(W)-copper(Cu) has been proposed as materials to meet both of the above characteristics. In the present study, the W-10wt.%Cu powders were synthesised by the mixing and hydrogen reduction of the starting mixture materials such as W-Cu, W-CuCl_2and WO_3-CuCl_2 in order to obtain the full densification. The W-10wt.%Cu produced by hydrogen reduction showed the higher interparticle friction than the simple mixed W-10wt%Cu because of the W agglomerates. In the dilatometric analysis the W-10wt.%Cu prepared from the W-CuCl_2was largely shrank by heating up 1400°C at the constant heating rate of 5°C/min. The possibility of application of metal injection molding (MIM) was also investigated for mass production of the complex shaped W-Cu parts in semiconductor devices. The relationship between the temperature of molding die and the pressure of injection molding was analyzed and the heating up stage of 120-290°C in the debinding process was controlled for the most suitable MIM condition.

[Korean]
The Effects of Mechanical Alloying Conditions on the Formation of Mn-sulfide: J Korean Powder Metall Inst. 2001;8(4):253-257.

Abstract PDF: The effects of mechanical alloying conditions on the formation of Mn-sulfide powders were analyzed. Impeller rotating speed, lubricant coating and added amounts of process control agent(stearic acid) were selected as a process control factor. MnS compounds are synthesized in 3 hours by mechanical alloying at the alternative milling condition. Discontinuous rotating speed of 1200rpm for 4 minutes and 1000rpm for 1 minute shows more effects on the compound formation of MnS. After coating of lubricant on the wall, elementary Mn and sulfur were partially remained by mechanical alloying. The friction effects of the wall and grinding media on the powders are significantly important to form the compound of MnS.

[Korean]
Transient Liquid Phase Bonding with Liquid Phase Sintered Insert Metals: J Korean Powder Metall Inst. 2001;8(4):258-267.

Abstract PDF: In this work, the conventional transient liquid phase(TLP) bonding was modified. An attempt was made of using a liquid phase sintered alloy, which will be a liquid phase coexisting with a solid phase at the bonding temperature, as an interlayer for bonding metals. With an aim of revealing the fundamental features of this modified TLP bonding, the kinetics concerned with the growth of solid particles and the isothermal solidification process in Fe-1.16wt%B and Fe-4.5wt%P interlayers for the bonding pure iron, as well as the morphological change of the solid particle, were investigated.

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