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- 저자 : Weissgaerber, (검색결과 5 건)
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Nanodispersion-Strengthened Metallic Materials
Weissgaerber, Thomas,Sauer, Christa,Kieback, Bernd The Korean Powder Metallurgy Institute 2002 한국분말재료학회지 (KPMI) Vol.9 No.6
Dispersions of non-soluble ceramic particles in a metallic matrix can enhance the strength and heat resistance of materials. With the advent of mechanical alloying it became possible to put the theoretical concept into practice by incorporating very fine particles in a flirty uniform distribution into often oxidation- and corrosion- resistant metal matrices. e.g. superalloys. The present paper will give an overview about the mechanical alloying technique as a dry, high energy ball milling process for producing composite metal powders with a fine controlled microstructure. The common way is milling of a mixture of metallic and nonmetallic powders (e.g. oxides. carbides, nitrides, borides) in a high energy ball mill. The heavy mechanical deformation during milling causes also fracture of the ceramic particles to be distributed homogeneously by further milling. The mechanisms of the process are described. To obtain a homogeneous distribution of nano-sized dispersoids in a more ductile matrix (e.g. aluminium-or copper based alloys) a reaction milling is suitable. Dispersoid can be formed in a solid state reaction by introducing materials that react with the matrix either during milling or during a subsequent heat treatment. The pre-conditions for obtaining high quality materials, which require a homogeneous distribution of small dis-persoids, are: milling behaviour of the ductile phase (Al, Cu) will be improved by the additives (e.g. graphite), homogeneous introduction of the additives into the granules is possible and the additive reacts with the matrix or an alloying element to form hard particles that are inert with respect to the matrix also at elevated temperatures. The mechanism of the in-situ formation of dispersoids is described using copper-based alloys as an example. A comparison between the in-situ formation of dispersoids (TiC) in the copper matrix and the milling of Cu-TiC mixtures is given with respect to the microstructure and properties, obtained.
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Carbon-Nanofiber Reinforced Cu Composites Prepared by Powder Metallurgy
Weidmueller, H.,Weissgaerber, T.,Hutsch, T.,Huenert, R.,Schmitt, T.,Mauthner, K.,Schulz-Harder, S. The Korean Powder Metallurgy Institute 2006 한국분말재료학회지 (KPMI) Vol.13 No.5
Electronic packaging involves interconnecting, powering, protecting, and cooling of semiconductor circuits fur the use in a variety of microelectronic applications. For microelectronic circuits, the main type of failure is thermal fatigue, owing to the different thermal expansion coefficients of semiconductor chips and packaging materials. Therefore, the search for matched coefficients of thermal expansion (CTE) of packaging materials in combination with a high thermal conductivity is the main task for developments of heat sink materials electronics, and good mechanical properties are also required. The aim of this work is to develop copper matrix composites reinforced with carbon nanofibers. The advantages of carbon nanofibers, especially the good thermal conductivity, are utlized to obtain a composite material having a thermal conductivity higher than 400 W/mK. The main challenge is to obtain a homogeneous dispersion of carbon nanofibers in copper. In this paper, a technology for obtaining a homogeneous mixture of copper and nanofibers will be presented and the microstructure and properties of consolidated samples will be discussed. In order to improve the bonding strength between copper and nanofibers, different alloying elements were added. The microstructure and the properties will be presented and the influence of interface modification will be discussed.
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Weidmueller H.,Weissgaerber T.,Hutsch T.,Huenert R.,Schmitt T.,Mauthner K.,Schulz-Harder J. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
For microelectronic circuits, the main type of failure is thermal fatigue. Therefore, the search for matched coefficients of thermal expansion (CTE) of packaging materials in combination with a high thermal conductivity is the main task for developments of heat sink materials electronics, and good mechanical properties are also required. The aim of this work is to develop copper matrix composites reinforced with carbon nanofibers to meet these requirements. In this paper, a technology for obtaining a homogeneous mixture of copper and nanofibers will be presented and the microstructure and properties of consolidated samples will be discussed.
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고상공정에 의해 제조된 AIN-Cu 나노복합재료의 조직 특성과 열팽창계수 측정에 관한 연구
Lee, Gwang-Min,Lee, Ji-Seong,Lee, Seung-Ik,Kim, Ji-Sun,Weissgaerber, T.,Kieback, B. 한국재료학회 2001 한국재료학회지 Vol.11 No.10
The present study was carried out to investigate the effect of MA processing variables on the microstructural properties of composite powders and the coefficient of thermal expansion of pulse electric current sintered AlN-Cu powder compacts. The AlN-Cu powders had a size of less than 15 $\mu\textrm{m}$ with 25 nm size of copper crystallite after MA 32 hours. The finely distributed AlN-Cu powder compacts were completely achieved after PECS. The residual oxygen was considerably removed after hydrogen reduction treatment. The residual carbon was completely removed to 97%. The CTE of AlN-Cu powder compacts showed a good consistency with Kingery-Tuner model when the volume fraction of copper was less than 60%. When it was more than 60%, the CTE had a good agreement with Series model.
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Synthesis of Intermetallics and Nanocomposites by High-Energy Milling
Bernd F. Kieback,H. Kubsch,Alexander Bohm,M. Zumdick,Thomas Weissgaerber The Korean Powder Metallurgy Institute 2002 한국분말재료학회지 (KPMI) Vol.9 No.6
Elemental powders are used in high energy milling processes for the synthesis of new compounds. The low temperature solid state reactions during milling in inert gas atmosphere may result in intermetallic phases, carbides, nitrides or silicides with a nanocrystalline structure. To obtain dense materials from the powders a pressure assisted densification is necessary. On the other side the defect-rich microstructure can be used for activated sintering of elemental powder mixtures to obtain dense bodies by pressureless sintering. Results are discussed for nanocrystalline cermet systems and for the sintering of aluminides and silicides.
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