Fracture Properties of SPS Tungsten Copper Powder Composites
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INTRODUCTION
TUNGSTEN-COPPER (W-Cu) composites are characterized by high thermal conductivity, low thermal expansion and high wear resistance combined with excellent electrical conductivity.[1] The high thermal conductivity of copper and the low thermal expansion coefficient of tungsten make W-Cu composites attractive for thermal management materials in microelectronic devices.[2] Some of the potential applications can be summarized in electrical applications and high voltage arc contacts such as, electronic application includes, heat sinks and spreaders, microwave carriers, hermetic package bases, ceramic substrate carriers, and laser diode mounts.[3] Tungsten-copper composites are also reported to be used in wireless telecommunication devices as well as other power and radio-frequency packages for the microelectronics industry.[4,5] However, the W-Cu system exhibits mutual insolubility or negligible solubility.[6] W-Cu powder compacts show very poor sinterability, even by liquid phase sintering above the melting point of the Cu phase.[6] The properties of composites depend strongly on the preparation method, particle size, and particle matrix interface adhesion. Particle size has a great role on the properties of the final composites. For example Bera et al.[7] have synthesized copper alloys with extended MEDHAT AWAD EL-HADEK, Associate Professor, is with the Department of Mechanical Design & Production, Faculty of Engineering at Port-Said, Port-Said University, Port-Fouad, PortSaid 42523, Egypt. Contact e-mail: [email protected] SALEH HAMADA KAYTBAY, Assistant Professor, is with the Department of Mechanical Engineering, Faculty of Engineering at Benha, Benha University, Benha, Egypt. Manuscript submitted August 31, 2011. Article published online September 19, 2012 544—VOLUME 44A, JANUARY 2013
solid solubility and nano Al2O3 dispersion by mechanical alloying and equal channel angular pressing. It was found that the copper-Al2O3 alloys[7] appear to have high-strength, wear/erosion-resistant and Cu-based electrical contacts with nano-ceramic dispersion. Furthermore, Bera et al.[8] have developed a wear-resistant Cu-Cr-Ag electrical contacts alloy with nano-Al2O3 dispersion by mechanical alloying and high pressure sintering. It was reported[8] that the hardness and wear resistance of the Cu-Cr-Ag alloy with nano-Al2O3 dispersion increase significantly with the addition of nano-Al2O3 particles. El-Hadek, and Kaytbay[9] have reported that copper-Al2O3 composites with nano size Al2O3 particles have the lowest electrical resistivity values. This was attributed to the higher densification, generating a break in the continuous copper matrix network. As the Al2O3 particles sizes in the metal increases, the failure stresses decrease.[9] This leads to the reduction of the elastic modulus with the increase of Al2O3 particles sizes. Approximately 75 pct reduction in the elastic modulus between composites with Al2O3 particle size 100 nm, and 20 lm was evident.[9] The classic conventional method for fabrication W-Cu composites
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