Papers by Keyword: Powder Metallurgy (PM)

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Authors: Kazunari Shinagawa, Y. Hirashima
Authors: K.E. Belyavin, D.V. Minko, N.V. Reshnetikov
Abstract: A technology of hardening porous materials of titan powders has been elaborated. The technology is based on passing alternating current with duration of ~10-1…101 s through porous (35…40%) blanks made by method of Sintering by Electric Discharge (SED) by passing a pulse of current with duration of ~10-5…10-3 s. The influence of technological regimes of porous blanks treatment on their structure and properties is investigated. Geometry and dimension of contact necks between powder particles of obtained samples are evaluated. Variations of porosity and strengths as well as microstructure of porous samples materials before and after treatment are investigated. Optimum range of treatment technological regimes is determined within which porosity of 30…35% with maximum strength values.
Authors: Luisa N. Mîtcă, Mustafa Günay, Radu Liviu Orban, Ulvi Şeker
Abstract: In this study, the machinability of the Cu matrix composites reinforced with 5, 10, 15 and 20 vol.% of Al2O3 particulates produced by powder metallurgy have been investigated. The effects of compaction pressure, sintering duration and volume fraction of reinforcing component on the surface roughness during machining of the considered composites, obtained by the appropriate Cu-Al2O3 powder mixtures cool die pressing at 500, respectively 700 MPa, and sintered at 800 °C for durations of 45 and 60 minutes in an argon atmosphere were determined. The machining tests were performed on a CNC machining centre, by means of samples face milling in dry conditions, at two different feed rates and four different cutting speeds, while the depth of cut was kept constant. As cutting tools have been adopted commercial grade (H13A) uncoated cemented carbide inserts manufactured by Sandvik Coromant with the geometry of TPKN1603 PP-R. After the machining tests, the surface roughness measurements clearly showed an increasing trend in surface roughness when the feed rate is increased from 300 mm/min to 400 mm/min for both sintering durations. Surface damages created on the machined surface through release from the matrix of particles negatively impact surface roughness. The most stable results in terms of surface roughness were obtained at 20% reinforcing ratio for 700 MPa compacting pressure and 60 minutes sintering duration.
Authors: Tungwai Leo Ngai, Yuan Yuan Li, Zhao Yao Zhou
Abstract: Increasing density is the best way to increase the performance of powder metallurgy materials. Conventional powder metallurgy processing can produce copper green compacts with density less than 8.3g/cm3 (a relative density of 93%). Performances of these conventionally compacted materials are substantially lower than their full density counterparts. Warm compaction, which is a simple and economical forming process to prepare high density powder metallurgy parts or materials, was employed to develop a Ti3SiC2 particulate reinforced copper matrix composite with high strength, high electrical conductivity and good tribological behaviors. Ti3SiC2 particulate reinforced copper matrix composites, with 1.25, 2.5 and 5 mass% Ti3SiC2 were prepared by compacting powder with a pressure of 700 MPa at 145°C, then sintered at 1000°C under cracked ammonia atmosphere for 60 minutes. Their density, electrical conductivity and ultimate tensile strength decrease with the increase in particulate concentration, while hardness increases with the increase in particulate concentration. A small addition of Ti3SiC2 particulate can increase the hardness of the composite without losing much of electrical conductivity. The composite containing 1.25 mass% Ti3SiC2 has an ultimate tensile strength of 158 MPa, a hardness of HB 58, and an electrical resistivity of 3.91 x 10-8 Ω.m.
Authors: Angela Popa, Irina Carceanu, Cristian Coman, Viorel Candea, Gabi Matache
Abstract: The present research’ goal is the fabrication of Fe-based composite reinforced with oxide particles with special characteristics (wear, friction coefficient) for friction applications usually the Fe-based composite are obtained through melting and castings followed by other finishing operations. These technologies do not ensure a homogeneous distribution of reinforcement particles and that is why, the authors approached a PM specific technologies to obtained Fe-based composite. The Fe-based powder reinforcement with oxide particles obtained through mechanical alloying the powder was analyzed and characterized and then underwent the operation of milling in the planetary milling with ball, pressing and sintering at different temperatures and durations. SEM analysis had of identifying the distribution compounds into the Fe- matrix, their quantitative evolution and the influence of different parameters. The mechanical characteristics, wear and friction coefficient, were determined.
Authors: Jean François Silvain, Valérie Denis-Lutard, Pierre Marie Geffroy, Jean Marc Heintz
Abstract: Today, there is a strong push to improve the thermal management of electronic components in order to increase the performance and the reliability of electronic devices. Up to now, most of the heat sinks are mainly made of Copper that presents a good thermal conductivity (TC) but a coefficient of thermal expansion (CTE) much higher than the ceramic of the DBC (direct bonding Copper). It induces interfacial thermal stresses and indeed it decreases the reliability of the global electronic system. Therefore, there is a strong need for the development of novel heat dissipation material having low CTE combined with high TC. Carbon fibres reinforced copper matrix offers a good compromise between thermo mechanical properties (i.e. CTE) and medium TC. In order to increase surface TC, pure Copper can be added on the top surface and/or on the bottom one of the composite heat sink playing the role of heat spreader for hot spots linked with the Si components. The fabrication technique of these materials is based on powder metallurgy technique. The thermal properties of adaptive materials, TC and CTE, have been measured for different Copper thicknesses and architectures ([C/Cu], [Cu – C/Cu] and [Cu – C/Cu – Cu]). Simulation of the TC and CTE have been performed and compared to the experimental results.
Authors: José M. Gallardo, Juan M. Montes, Francicso Gomez Cuevas
Authors: Gyu-Sam Shim, Mok Soon Kim, Won Yong Kim, Hiroshi Yamagata
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