Journal of Powder Materials

Volume 7(1); February 2000

Thermoelctric Propretries of Bi2Te3 Fabricated by Mechanical Grinding-Mixing Process: J Korean Powder Metall Inst. 2000;7(1):6-11.

79 View
0 Download

Abstract PDF: Two kinds of Bi2Te3 powders, pure Bi2Te3/2vol.%ZrO2, have been prepared by a mechanical grinding process process. Effect of mixing of the powders on thermoelectric of the sintered body has been investigated by measuring Seebeck Coeffcient, specific electric resistivity and thermal conductivity. With an increase in the weight fraction of the Bi2Te3/2vol.%ZrO2 powder from 0 to 40wt.%. Especially, the figure of merit of the mixedBi2Te3 sintered body increases and thereafter dedreases above 40wt.%. Especially. the figure of merit of the mixed Bi2Te3 sintered bodies with mixing of Bi2Te3/2vol.%ZrO2 powder increased about 1.3time in comparison with the value of the specimen before mixing. Mixing of two kinds of Bi2Te3 powders which have different theramal and electric propertries with each other seemed to be useful methob to increase the figure of merit of Bi2Te3 sintered body.

Effect of the Microstructrure of Rapidly Solidified Al-Pb-Cu-Mg on the Wear ProPerty: J Korean Powder Metall Inst. 2000;7(1):12-18.

80 View
0 Download

Abstract PDF: Effects of the microstrucrure of rapidy solidified Al-Pb-Cu-Mg alloys on the wear investigated. In order to overcome the miscility gap between Al and pb under equilibrium conditions, both in the solid and the liquid states, the alloy were rapidy solidifies to produce them in a segregation-free condition. Although the Pb particles showed relatively fine dispersion in the Al matrix in all the alloys by this process. the Al-16Pb alloy was found to have the most favorable microstructure with discretre with discrete Pb particles of abount 0.5 µm in size. With the addition of Cu and Cu-Mg to Al-16Pb, cellular structures were newly formed; not seen in the binary Al-Pb alloy. Wear properties of the Al-Pb binary alloys measured as a function of the sliding speen, sliding distance, and applied load showed that the Al-16Pb alloy has the best wear resistance, as expected from the fine microstructural features in this alloy. The were resistance of the alloy containing Cu-and Cu-Mg was higher than that of the Al-16Pvb alloy, due to matrix strengthening by precipitation hardeing. The wear mechanism was identified by examining the traces and wear debris.

Effect of Milling Temperature on Formation of Al-Cr-Zr Metal Powder: J Korean Powder Metall Inst. 2000;7(1):19-26.

73 View
0 Download

Abstract PDF: Al-Cr-Zr metal powders were prepared by cryo-milling(-75°C),ambi-milling(25°C) and warm-milling(200°C) to investige the effect of milling temperature. The morphogical changes and microstructural evolution of Al-6wt.%Cr-3wt.%Zr metal powder ball milling were investigated by SEM, OM and XRD. The cryo-milling at -75°C caused the more refinement of powder particle size than ambi-milling and warm-milling. The partic morpholgy of Al-Cr-Zr metal powders changed changes into spheroidal particles at 25°Cand spherical particles at 200°CThe spherical particles were formed by agglomertion and contiuous wrapping of the spheroidal particles. The calculated Al crystallite size in Al-Cr-Zr metal powders by the Scherer equation were refined rapidly for short milling time -75°Ccompared with milling at 25°C and 200°C.

Fabrication Process and Mechanical Properties of High Volume Fraction SiC Particle Preform: J Korean Powder Metall Inst. 2000;7(1):27-34.

74 View
0 Download

Abstract PDF: The fabrication process and mechanical properties of SiC particle prefrrms with high volume fraction ranged 50∼71% were investigated to make metal matrix composites for possible applications as heat sinks in electronic packares. The SiC particle preforms with 50∼71vol% of reinforcement were fabricated by a new modified process named ball milling and pressing method. The SiC particle performs were fabricated by ball milling of SiC particles with single sized of 48µm in diameter or two different size of 8µm and 48µmin diameter, with collodal SiO2 as inorgnic binder in distilled water, and the mixed slurries were cold pressed for consolidation into final prefom. The compressive strengths og calcined SiC particle prefoms increased from 20MPa to 155MPa with increasing the content of inorganis binder, temperature and time for calcination. The increase of compressive strength of SiC particle bridge the interfaces of two neighboring SiC particles.

Mechanical Properties of 2024/(Al2O3.SiC)p Composite Reinforced with Al2O3.SiC Particle Prepared by SHS Process: J Korean Powder Metall Inst. 2000;7(1):35-41.

84 View
1 Download

Abstract PDF: Al2O3.SiC particle was prepared was prepared by the self-propagting high temperature sYthesis(SHS) process from a mixture of SiO2, Al and C powders, The fabricated Al2O3.SiC particle was applied to 2024Al/(Al2O3.SiC)pcomposite as a reinforcement. Aluminum matix composites were fabricares by the powder extrusion method using the synthesized Al2O3.SiC particle and commercial 2024Al powder. Theoptimum preparation conditions for Al2O3.SiC partticle by SHS process were described. The influence of the Al2O3.SiC voiume fraction on the mechanical was composite was also discussed. Despite adiabatic temperature was about 2367K, SHs reaction was completed not by itself, but by using pre-heating. Mean particle size of final particle synthesized was 0.73 µm and most of the particle was smaller than 2µm. Elastic modulus and tensile strength of the composite increased with increase the volume fraction of reinforcement but, tensile strength depreciated at 30 vol% of reinforcement.

A Study on Densification Behvior of Austenitic Stainless Steel Powder Compacts Processed by Warm Compaction: J Korean Powder Metall Inst. 2000;7(1):42-49.

81 View
0 Download

Abstract PDF: Densificationbehavior of conventional austenitic stainless steel powder compacts was studied by comparing the relative density of sintered compact(Ds)with that of green compacts(Dg)prepared with various catbon contents and P/M process. Dg of 304and 316 powders by warm compaction under pressure of 686 MPa at heating temperature of powder(553K) and dies (573K) were 80% and 81%, repectively, whichwere 2 and 3% higher than those of conventional green compacts at the same pressure. Ds of 304 compacts sintered at 1373K in H2 gas has the same value of 84% max. regardless of compacting temperature, and Ds of 316 compacts at the same sintering conditions were 80% by conventional compaction and 83% by warm compaction. Oxygen contents of 304 and 316 sintered compacts were increased 1.43∼2.94% and 0.010∼0.921% higher than those of raw powders and warm green compacts, respectively. In other case, Ds of 316 compacts sintered at 1573K in vacuum had the same value of 86%max. And Ds of 316 compacts at the same sintering conditions were 83% and 86% by conventional and warm compaction, respectively. Oxygen contents of 304 sintered compacts were 0.321% and 0.360%, and in case of 316, they were 0.419% and 0.182% by the respective compating condition. With carbon additions in the range 0.1∼0.6% Ds increased to the extent of 86∼89% in 304 sintered compacts, and to 82∼84% and 85∼87% in 316 according to different two compacting peocesses compared to those of sintered compacts without carbon addition.

Improvement in Sinterability Iorn-Copper- Tin Compact: J Korean Powder Metall Inst. 2000;7(1):50-54.

107 View
0 Download

Abstract PDF: In order to reduce the sintering temperature of iron based sintered parts, sinteing properties of iron-copper prealloyed powder were investigated at various temperatures in the range of 700∼890°C, and than the rusults were compared with those of the conventional iron-copper-tin compact using elemental powders, The using of prealloyed as a new process improved its sintering performance at lower temperature than elemental powder as the conventional process. The relative sintered density and radial crushing stength of the compact using prealloyed were higher than those of using elemental powder at all sintering temperature. For example, the radial curength of the compact using powder was about 50kg/mm2 at 700°C, while that of the compact using elemental powder sintered at 890°C was 43kg/mm2.

First
Prev
Page of 1
Next
Last

Previous issues