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- Volume 9(1); February 2002
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- Synthesis and Applications of Nano-powders
- J Korean Powder Metall Inst. 2002;9(1):1-10.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.001
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- Effect of ECAP on Microstructure of SiCw/6061Al Composites Produced by Powder Metallurgy
- Si-Young Chang
- J Korean Powder Metall Inst. 2002;9(1):11-18.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.011
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Abstract
PDF - The 6061 Al alloy based composites reinforced with 10 vol% SiC whiskers were prepared by powder metallurgy with the powders having the different sizes, i.e. < 30µm and > 30µm The composites were subjected to equal channel angular pressing (ECAP) at various conditions and the microstructural changes during ECAP were examined In the composites SiC whiskers were clustered and randomly aligned. The clusters were relatively well distributed in the composite with the smaller initial powder size. After ECAP, the clusters were aligned parallel to flow direction and became smaller. In addition, the shape of clusters was changed from irregular to round. The microstructure of the ECAPed samples were compared with those of the conventionally hot-extruded composites. The uniform microstructure and enhanced microhardness could be obtained by using the powders having the smaller size, decreasing ECAP temperature and repeating ECAP.
- Nanocrystallization Behavior of Al-Y-Ni with Cu Additions
- J Korean Powder Metall Inst. 2002;9(1):19-24.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.019
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- This paper reports the results of an investigation into the effect of Cu additions upon the nano-crystallization behaviour of an Al-Y-Ni alloy. 1 at.% Cu was added to a base alloy of Al/sub 88/Y₄Ni/sub 8/ either by substitution for Al to form Al/sub 87/Y₄Ni/sub 8/Cu₁, or by substitution for Ni to form Al/sub 88/Y₄Ni/sub 7/Cu₁. Consistent with previous findings in the literature, the substitution of Cu for Al was found to increase the thermal stability of the amorphous phase whereas the substitution of Cu for Ni was found to decrease its thermal stability. Comparing the microstructures of these alloys after heat treatment to produce equivalent volume fractions of Al nanocrystals showed average grain sizes of 14 nm, 12 nm and 9 nm for the alloys Al/sub 88/Y₄Ni/sub 8/, Al/sub 87/Y₄Ni/sub 8/Cu₁respectively. The effect of Cu in refining the size of the nanocrystals was attributed to enhanced nucleation increasing the number density of the nanocrystals, rather than diffusion limited or interface limited growth.
- Solid State Reduction of Haematite by Mechanical Alloying Process
- J Korean Powder Metall Inst. 2002;9(1):25-31.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.025
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- The efects of mechanical aloying conditions and the type of reducing agent on the solid state reductionof haematite Fe_2O_3 have been investigated at room temperature. Aluminium titanium zinc and copper were used as reducing agent. Nanocomposites of metal-oxide in which oxide particles with nano size were dispersed in Fe matrix were obtained by mechanical alloying of Fe_2O_3 with aluminium and titanium respectively However the reduction of Fe_2O_3 by coppe was not occurred Composite materials of iron with Al_2O_3 and TiO_2 were obtained from the system of Fe_2O_3-Al and Fe_2O_3-Ti after ball milling for 20 hrs and 30 hrs respectively. And the system of Fe_2O_3-Zn resulted in the formationof FeO with ZnO after ball milling of 120 hrs. The final grain sizes of iron estimated by X-ray diffraction line-width measurement were in the ranges of 24~33 nm.
- Effects of Convection Gas on Formation of Sn Oxide Nanoparticles
- Niihara K.
- J Korean Powder Metall Inst. 2002;9(1):32-37.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.032
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- In the present study of IGC (Inert Gas Condensation) evaporation-condensation processing study, the effects of IGC convection gas on the crystallographic structure, size and shape of tin oxide nanoparticles were investigated. In addition, the phase transformation of tin oxide nanoparticles was studied after heat treatment. IGC processing was conducted at 1000℃ for 1 hr. The mixture gas of oxygen and helium was used as a convection gas. Metastable tetragonal SnO nanoparticles were obtained at a lower convection gas pressure, whereas amorphous tin oxide nanoparticles were obtained at a higher one. The formation of amorphous phase could be explained by the rapid quenching of the vaporized atoms. The resultant nanoparticles size was about 10 nm with a rounded shape. The tin oxide nanoparticles prepared by IGC were almost transformed to the stable tetragonal SnO₂ after heat treatment.
- Formation of Pores during Sintering of Lead Borosilicate Glass Frits
- J Korean Powder Metall Inst. 2002;9(1):38-42.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.038
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- Effects of chemical compositions on the sintering behavior of the lead borosilicate glass developed for barrier ribs of plasma display panels were investigated in this study. Formation of pores during sintering of the glass was noted and their formation mechanism was investigated using XPS, TG/DTA, and XRD. The results indicated that pores are formed by the oxygen released from Pb-oxides during sintering.
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Citations
Citations to this article as recorded by
- Densification and Dielectric Properties of Glass/Ceramic Composites Sintered with Various Borosilicate Glass
Sang Ok Yoon, Kwan Soo Kim, Shin Kim, Sang Heung Shim, Jong Guk Park
Materials Science Forum.2007; 544-545: 961. CrossRef
- Densification and Dielectric Properties of Glass/Ceramic Composites Sintered with Various Borosilicate Glass
- Microstructural and Mechanical Characteristics of the ECAPed P/M 6061 Al Alloy
- J Korean Powder Metall Inst. 2002;9(1):43-49.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.043
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- Microstructural and mechanical characteristics of P/M 6061 Al alloy subjected to equal channel angular pressing (ECAP) were investigated. The P/M 6061 Al alloy had an intial grain size of approximately 20mutextrmm. An equiaxed ultra-fine grained structure with the mean grain size of ~50 mutextrmm was obtained by four repetitive ECAP at 473 K. The microhardness of P/M 6061 Al alloy was drastically increased from about 40 Hv to 80 Hv by two repetitive ECAP at 373 K. However, the microhardness decreased with increasing ECAP temperature. The tensile stength of as-hot-pressed P/M 6061 Al alloy before ECAP was 95 MPa, whereas it increased to both 248 MPa after two repetitive ECAP at 373 K and 130 MPa after four repetitive ECAP at 473 K. The tensile properties of the ECAPed sample were compared with those of commercial cast 6061-O and 6061-T4 Al alloys.
- On the Fabrication of Porous 316L Stainless Steel by Spark Plasma Sintering
- J Korean Powder Metall Inst. 2002;9(1):50-60.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.050
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- SPS(Spark Plasma Sintering ) is known to be an excellent sintering method for porous materials. In the present work an attempt has been made of fabricating porous 316L Stainless steel with good mechanical properties by using controlled SPS process Porosity was 21%~53% at sintering temperature of 600°C~1000°C The limit of porosity with available mechanical strength was 30% at given experimental conditions. Porosity can be controlled by manipulating the intial height of the compact by means of the supporter and punch length. The applied pressure can be exerted entirely upon the supporter, giving no influence on the specimen. The specimen is then able to be sintered pressurelessly. In this case porosity could be controlled from 38 to 45% with good mechanical strength at sintering temperature of 900°C. As the holding time increased, neck between the particles grew progressively, but shrinkage of the specimen did not occur, implying that the porosity remained constant during the whole sintering process.
- 기계적합금화법의 진전과 응용현황
- J Korean Powder Metall Inst. 2002;9(1):61-65.
- DOI: https://doi.org/10.4150/KPMI.2002.9.1.061
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