Browsing by Author "Shu, KM"

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Fabrication and characterization of Cu-SiCp composites for electrical discharge machining applications
(2001)
Shu, KM
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Tu, GC
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材料科學與工程學系
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Department of Materials Science and Engineering
Cu-SiCp composites made by the powder metallurgy method were investigated. To avoid the adverse effect of Cu-SiCp reaction, sintering was controlled at a reaction temperature less than 1032 K. Electroless plating was employed to deposit a copper film on SiCp powder before mixing with Cu powder in order to improve the bonding status between Cu and SiC particles during sintering. It was found that a continuous copper film could be deposited on SiCp by electroless copper plating, and a uniform distribution of SiCp in Cu matrix could be achieved after the sintering and extrusion process. The mechanical properties of Cu-SiCp composites with SiCp contents from 0.6 to 10 wt% were improved evidently, whereas electrical properties remained almost unchanged as compared with that of the pure copper counterpart. In the electrical discharge machining (EDM) test, the as-formed composite electrodes exhibited a character of lower electrode wear ratio, justifying its usage. The optimum conditions for EDM were Cu-2 wt% SiC. composite electrode operating with a pulse time of 150 mu sec.
Study of electrical discharge grinding using metal matrix composite electrodes
(2003-06-01)
Shu, KM
;
Tu, GC
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材料科學與工程學系
;
Department of Materials Science and Engineering
An investigation was made into the combined technologies of electrical discharge machining and grinding (EDMG). A metal matrix (Cu/SiCp) electrode with a rotating device was made and employed to study the EDMG technology. It was found that 3-7 times the normal electrical discharge machining (EDM) material removal rate (MRR) could be achieved in EDMG under suitable conditions of electrode rotating speed, SiCp particle size and current. This novel achievement is attributed to the fact that, under appropriate conditions, the hump-shaped melted material created by the EDM mechanism is vulnerable to attack by the grinding mechanism during the EDMG operation, greatly increasing the removal rate. Conversely, under inappropriate conditions, in which hump-shaped material solidifies prior to the non-conductive ceramic particle grinding, the above function becomes negligible and results in much lower MRR. (C) 2003 Elsevier Science Ltd. All rights reserved.
The microstructure and the thermal expansion characteristics of Cu/SiCp composites
(2003-05-25)
Shu, KM
;
Tu, GC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Copper/silicon carbide composites (Cu/SiCp) were made by the powder metallurgy method. Electroless plating was employed to deposit a copper film on SiCp powder before mixing with Cu powder in order to improve the bonding status between Cu and SiC particles during sintering. Thermal expansion property of as-formed product was measured in the temperature range from 50 to 550 degreesC. The results showed that copper coating on silicon carbide particles could render uniform distribution of SiCp in the copper matrix. The composites exhibited positive thermal hysteresis behavior when cooled down from the peak temperature to room temperature, which can be explained in terms of the residual stresses and the interfacial bonding between copper and silicon carbide. The magnitude of this strain was a function of the SiCp volume fraction and the number of thermal cycles. The thermal expansion property of composites was measured and compared with those predicted from various theoretical models. (C) 2002 Published by Elsevier Science B.V.