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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Journal of Korean Powder Metallurgy Institute
Journal Basic Information
Journal DOI :
Korean Powder Metallurgy Institute
Editor in Chief :
Jin Cheon Kim
Volume & Issues
Volume 5, Issue 4 - Dec 1998
Volume 5, Issue 3 - Sep 1998
Volume 5, Issue 2 - Jun 1998
Volume 5, Issue 1 - Mar 1998
Selecting the target year
The Effect of Ni Addition on the Sintering Kinetics of Ball-milled Mosi
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 241~249
Sintering kinetics of ball-milled
was studied with the addition of Ni.
powder with the average particle size of 1
was obtained from ball-milling of 10
powder. Small amount of Ni was added to the ball-milled
powder by salt solution and reduction method. The powder was compacted into cylindrical shape at 200 MPa and isothermally sintered in a
atmosphere at the temperature range of 1100~
for 3~600 minutes. The changes of linear shrinkage and sintered density were monitored as a function of sintering time. The microstructure was observed by using optical microscopy and scanning electron microscopy. Phases were identified by X-ray diffratometer and electro-probe micro analysis. Sintering kinetics of Ni-added powder was compared to as-milled powder and the apparent activation energy was calculated from Arrhenius plot.
Synthesis of Titanium Silicides by Mechanical Alloying
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 250~257
The synthesis of titanium silicides (
and TiSi) by mechanical alloying has been investigated. Rapid, self-propagating high-temperature synthesis (SHS) reactions were observed to produce the last three phases during room-temperature high-energy ball milling of elemental powders. Such reactions appeared to be ignited by mechanical impact in an intimate, fine powder mixture formed after a critical milling period. During the high-energy ball milling, the repeated impact at contact points leads to a local concentration of energy which may ignite a self-propagating reaction. From in-situ thermal analysis, each critical milling period for the formation of
and TiSi was observed to be 22, 35.5 and 53.5 min, respectively.
, however, have not been produced even till the milling period of 360 min due to lack of the homogeneity of the powder mixtures. The formation of titanium silicides by mechanical alloying and the relevant reaction rates appeared to depend upon the critical milling period, the homogeneity of the powder mixtures, and the heat of formation of the products involved.
Initial Sintering Behaviour of the Powder Injection Molded W-15wt%Cu Nanocomposite Powder
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 258~264
The initial sintering behaviour of the powder injection molded (PIMed) W-l5wt%Cu nanocomposite powder was investigated. The W-Cu nanocomposite powder was produced by the mechanochemical process consisting of high energy ball-milling and hydrogen reduction of W blue powder-CuO mixture. Solid state sintering of the powder compacts was conducted at
for 2~10 hours in hydrogen at mosphere. The sintering behaviour was examined and discussed in terms of microstructural developments such as W-Cu aggregate formation, pore size distribution and W grain growth. The volume shrinkage of PIM specimen was slightly larger than that of PM(conventional PM specimen), being due to fast local densification in the PIM. Remarkable decrease of carbon and oxygen in the PIM enhanced local densification in the early stage of solid state sintering process with eliminating very fine pores less than 10 nm. In addition, such local densiflcation in the PIM is presumably responsible for mitigating of W-grain growth in the initial stage.
Effect of Sintering Atmosphere and Carbon Addition on Sintered Density of M3/2 Grade High Speed Steel Powder
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 265~272
For the purpose of investigating the effect of sintering atmosphere and carbon addition on sintered density and microstructural characteristics, the M3/2 grade high speed steel powders with the addition of carbon are sintered in vacuum and
gas atmosphere. With the addition of 0 wt%C, 0.45wt%C and 1.15 wt%C the optimum sintering temperatures decrease down to
respectively for the vacuum sintered specimen, and also decrease down to
for the gas sintered specimen. The threshold temperatures for full densification decrease steeply with increasing carbon content of the sintered specimen, while this temperatures are slowly decreased at high carbon content. The vacuum sintered specimen shows the primary carbides of MC and
type at the optimum sintering temperature, and eutectic carbides of
and Fe-Cr type are produced in the oversintered specimen. The gas sintered specimen exhibits M6C and Fe-Cr type primary carbides at the optimum sintering temperature. The eutectic carbides of
and Fe-Cr type and MX type carbonitride are shown for the oversintered specimen in the gas atmosphere. The hardness of gas sintered specimen shows high value of 830-860 Hv due to the increment of carbide precipitation.
Microstructures and Repeated Usage-Properties of de-
Transition Metals/ZSM-5 Catalyst Made by Mechanical Alloying Method
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 273~278
transition metals(Cu, Co)/ZSM-5 catalyst was made by mechanical alloying method, and their microstructures and repeated usage-properties were investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The conversions ability of NO in the catalyst was measured. A part of ZSM-5 in CO/ZSM-5 composite powders was amorphous and the amorphous phase became less stable with increasing Co content. Conversion ability of NO in 10Cu/ZSM-5 powders decreased from 89% to 12% and that in 10Co/ZSM-5 decreased from 22% to 17% by 7 times conversion tests.
Microstructures and Mechanical Properties of HIPed Submicron WC-(5~20) mass% Co Cemented Carbides
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 279~285
The microstructures and mechanical properties of submicron WC-Co cemented carbides were investigated in relation to cobalt content. To inhibit the WC grain growth during sintering, VC was added as a inhibitor in each alloy with 3 mass% to the cobalt content. The WC-(5, 8, 10, 15, 20) mass% Co compacts were sintered at
for 30 min in vacuum. Some of WC-(5, 8, 10) mass% Co sintered compacts were HIPed with 120 atm at 130
for 1 hr. The shrinkages of all HIPed alloys were increased without depending on the cobalt contents and the sintered densities of them. The relative densities of the alloys were increased with the cobalt content and HIPing. The less the cobalt content, the larger the WC grain. Many contiguities of WC grains were found in WC-5 mass% Co alloy. The sizes and numbers of pores in the alloys were decreased by HIPing. And also the strength and the hardness of each alloy were increased. The maximum hardness was about 18.95 GPa in the WC-5 mass% Co alloy HIPed and the maximum transverse-rupture strength (T.R.S.) 3.2 GPa in the WC-20 mass% Co alloy sintered.
Microstructures and Mechanical Properties of
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 286~292
Al intermetallic compound has been tested as a binder phase, in order to improve the oxidation resistance and the mechanical properties of TiC-Ni cermet at a high temperature. The wettability of
on TiC and the optimum sintering condition were investigated in TiC-(30, 40) vol%
cermets with the sintering temperature (1380~
) and time (30~99 min). The results are summarized as follows: 1) Ni
Al showed good wettability on TiC above
; 2) The shrinkages of the specimens increased with the sintering temperature, the sintering time and the binder content, whereas the relative densities were decreased; 3) Any other phase did not appeared in the microstructures of all sintered cermets. The grain sizes of TiC became larger as the sintering temperature and the sintering time as well as the binder content increased; 4) The hardness of the cermets decreased with increase in the sintering temperature and the sintering time as well as the binder content; 5) The transverse-rupture strength of the cermets increased with the sintering temperature and the sintering time, whereas it decreased with the binder content.
Improvments in Cost Reduction for Vacuum Sintering and Vacuum and Overpressure Sintering for Tungsten Carbides
Ermel, Dieter ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 293~298
In all larger hardmetal workshops furnaces for dewaxing, vacuum sintering or vacuum and overpressure sintering are today's standard. The furnace technology is well established. Equipment specifications such as operating overpressure, determine sintering cost, product quality, safety and reliability of the furnace and ultimately influence the competitiveness of the hard metal procucer in the global market. Essential furnace requirements are an efficient utilization of the furnace, an environmental friendly dewaxing system, high temperature uniformity, metallurgical treatment with process gases, as well as reduced cooling time by means of rapid cooling. Examples of reduced sintering costs are described achieved using a new design of vacuum sintering furnace with an improved rapid cooling device, cooling times are reduced by up to 45%. Additionally, a cost comparison of two different designs of vacuum overpressure sintering furnaces are included.
The factors of dimensional change of Fe-Cu-C sintered objects
Fujinaga, Masashi ; Suzuki, Yoshitomo ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 299~302
Dimensional accuracy is one of the most important issues in the production of sintered parts. The iron-copper-carbon system is commonly used alloys in sintered structural parts production. The dimensional control of these alloys, however, is not easy because of their complex sintering behavior. This study is an effort to clarify the influence of common factors on dimensional change of Fe-Cu-C sintered structural parts. We determined the effect of such various parameters as chemical composition, particle diameter, compact density, sintering temperature and sintering time on dimensional changes. Consequently, we obtained a useful formula to predict the final dimension in function of these parameters. The effect of typical impurities in copper powder on the dimensional change of sintered parts has also been described.
Recent Development of Science and Technology of Hard Materials in Japan
Hayashi, Koji ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 303~311
Hard materials such as hardmetal, coated hardmetal, cermet, ceramics and diamond or c-BN sintered compact are a kind of grain-dispersed alloy with high volume of hard particles. These are used for cutting tools, wear-resistant tools, rock bits, high pressure apparatus, etc. The annual production in Japan is about 1.7 billion dollars (200 billion yen). This is greatly owed to the development in science and technology which has been accomplished by applying new concepts such as fine or uniform grain microstructure, orientation of crystal grains, functionally graded material, artificial lattice and coherent bonding in recent years. In this review, the development in recent years in Japan is briefly summarized.
Effect of Mechanical Alloying on Combustion Densification of MoSi
Park, Hyung-Sang ; Park, Jin-Seong ; Ka, Mi-da ; Shin, Kwang-Seon ; Kim, Yong-Seong ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 312~318
The effect of the mechanical alloying of elemental Mo and Si powders on the combustion densification behavior of MoSi
was investigated. The ignition temperature of the combustion reaction of the mechanically alloyed powder was measured to be significantly lower than that of the powder mixture prepared by the low energy ball milling process. The densification of the products after the combustion reaction under compressive pressure from the mechanically alloyed powders, however, was found to be poorer than that of the products from the ball milled powder.
Powder Forging of Rapidly Solidified hi-Si Alloy with Back Pressure
Kohno, T. ; Kawase, K. ; Otsuki, M. ; Morimoto, K. ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 319~323
Powder forging with a back pressure was investigated for production of automobile and compressor parts made of a rapidly solidified Al-Si alloy powder. Disk-shaped green compacts made of a rapidly solidified Al-Si alloy powder were hot forged, and hubs were formed by loading back pressure on their top. The influences of the back pressure and die temperatures on forgeabiliy and properties of parts made of a rapidly solidified Al-Si alloy powder were examined. This method was also applied to the production of a scroll part. The results of these studies are summarized as follows : 1. A back pressure on the hub top is very effective for consolidation and preventing crack formation in the hub. 2. When a back pressure tess than 98 MPa is applied, the forging pressure increases by the same amount of the applied back pressure. With more than 98 MPa, the forging pressure increases further due to an increased friction at the hub side. 3. Die temperatures higher than approximately 670k are needed in order to consolidate well the hub top without cracks.
Computer Simulation of Sintering and Grain Growth
Matsubara, Hideaki ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 324~328
This paper is aimed to study the computer simulation of sintering process for ceramics by Monte Carlo and molecular dynamics methods. Plural mechanisms of mass transfer were designed in the MC simulation of sintering process for micron size particles; the transfer of pore lattices for shrinkage and the transfer of solid lattices for grain growth ran in the calculation arrays. The MD simulation was performed in the case of nano size particles of ionic ceramics and showed the characteristic features in sintering process at atomic levels. The MC and MD simulations for sintering process are useful for microstructural design for ceramics.
Development of Tungsten Dispersed Copper Based Alloy and its Physical Property
Mishima, Akira ; Sakaguchi, Shigeya ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 329~333
Copper-10 wt. % tungsten alloyed powder was obtained by co-reduction of mixed tungsten-trioxide and copper oxide powders at 973 K for 7.2 Ks. In the alloy obtained by pressure-assisted sintering of this co-reduced powder, ultra fine tungsten particles (about 100nm) were dispersed uniformly in the copper matrix. At room temperature, the hardness of this alloy was Hv151 and the electrical conductivity was 85% IACS. After annealing at 1173 K for 3.6 Ks, the hardness and electrical conductivity were Hv147 and 84% IACS, respectively, and were same as before annealing. It was confirmed that the hardness and electrical conductivity of this alloy were hardly influenced by annealing condition since the microstructure of this alloy is highly stabilized.
Microstructure and Properties of Nano-Sized Ni-Co Particulate Dispersed
Oh, Sung-Tag ; Mutsuo Sando ; Koichi Niihara ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 334~339
In purpose of introducing the inverse magnetostrictive properties into the structural ceramics,
based nanocomposites dispersed with nano-sized Ni-Co particles were studied. The composites were fabricated by the hydrogen reduction and hot-pressing of
and NiO-CoO mixed powders. The mixtures were prepared by using Ni- and Co-nitrate
as source materials for the Ni-Co particles. Microstructural observations revealed that nano-sized Ni-Co particles were dispersed homogeneously at
grain boundaries. High strength above 1 GPa was obtained for the
wt% Ni-Co nanocomposite fabricated by a controlled powder preparation process. The inverse magnetostrictive response to applied stress was obtained due to the presence of dispersed Ni-Co particles, which indicates a possibility to incorporate new functions into the structural ceramics without loosing the mechanical properties.
Advancement in Powder Metallurgy of Aluminum Alloys
Takeda, Yoshinobu ;
Journal of Korean Powder Metallurgy Institute, volume 5, issue 4, 1998, Pages 340~344
Along with the growth of conventional ferrous powder metallurgy (PM), PM of aluminum alloys has been intensively investigated in Japan. Although rapidly solidified aluminum alloy powder was first used in the USA,/sup 1)/ commercialization for consumer market was first realized in Japan./sup 2)/ In order to achieve the viable cost-performance including Near Net Shape (NNS) formability, we developed three processes, powder extrusion, powder forging and sintering. The new powder extrusion process does not use either capsulation or vacuum degassing. The new powder forging does not need lateral flow. The new sintering process does not use liquid phase. The performance achieved by the processes is outstanding mechanical or physical properties that has potential to substitute cast iron, steel, titanium Metal Matrix Composite (MMC) or Ingot Metallurgy (IM) aluminum alloys. Cooperation with customers, powder suppliers and research associations contributed to the advancement of PM aluminum alloys in Japan.