Tungsten Copper Superfine Powder Fully Dense Act

With excellent thermal and electricity behaviorm, high strength and hardness, W-Cu composites have been used widely in the fields of electrical materials, electron, ordnance industry and spaceflight. Along with the further progress on the electronic industrial, the need of high performance W-Cu composite is more and mare urgently.
However, because of the mutual insolubility between W and Cu, it is difficult to get densified W-Cu composites by traditional methods. In this dissertation, Salgel and spray drying are used to prepare ultrafine W-Cu composite powders. And then produce the W/Cu composite material by Compression Molding and Powder Injection Molding sintering method. The powder and the sintered composite have been studied by means of SEM、EDX, Chemical composition and Lsser instrument for thermal conduction, and discussion of garameters, which can  affect the proprieties and microstructure of W/Cu composites, the following main results can be obtained.

Firstly, tungsten copper superfine powder fully dense act is the series of W/Cu ultrafine composite powders were synthesized by sol-spray drying, calcination and subsequent hydrogen reduction process with reaction of ammonium paratungstate and copper nitrate. Through comparative analysis, a better craft is: copper nitrate 5.448, ammonium paratungstate 18.38g, citric acid 3.50g, deionized water 30m1, and then mix them under 90℃ in a beaker until it change to gel, and then dry it by spray drying tower, the collected precursor power were calcined under 600℃ with a furnace in the air, and reduction it under 800℃ at last. The morphology of the powder on the scanning electron microscope, found that the powder has the following characteristics: its shape present spherical; the particle diameter were under lum; the W and Cu phase distributes homogeneously.

Secondly, the series powder were melded to green parts by micro-isostatic press, and then sintered under different temperature. The density of the sintered compacts was measured using the Archimedes method, the microstructure of sintered body was observed by scanning electron micrascope (SEM). The physical and electrical properties o, the obtained W-Cu composites wore also tested. It was found that: the powders' Maximum pressure molding is 350MPa; the best sintering temperature: W-10Cu is 1350℃，W-15Cu is 1350℃，W-20Cu is 1200℃, W-25Cu is 1200℃，W-30Cu is 1150℃，W-60Cu is 1120℃，the relative density reach almost 99%, and the
W particles and Cu phase distributes homogeneously in the parts; The electrical conductivity of thesintered bodies increased with the copper content and the relative increase of the density, but the Rockwell hardness of the sintered bodies reduced with the copper content.

Thirdly, for developing W-Cu thermal management components in complex shapes, MIM process has been tested by using the W-10Cu ultrafine composite powder. The poor flowability of the powder leads to a law critical solid loading as 47 vol.% with 2IN .m of Torque for MIM feedstock. However, experiments based an the feedstock with solid loading of 45 vol.% have been successfully carried out and no defects are found in injection and dehinding stages, and the best sintered temperature is 1400℃，The relative density of sintered parts reaches 99% and no Cu is extruded to the surface of the parts during sintering.

Lastly, the thermal properties、conductivity、Rockwell hardness and the microstructure of the mold pressing parts, MIM parts and the Cu infiltration parts were studied. It found that: the relative density of the MIM parts (99.3%) is a litter more than the mold pressing parts(98.9%) .Microstructures of the MIM parts using W-10Cu ultrafine composite powder are more homogeneous than those of the mold pressing parts and Cu infiltrated parts. Due to more homogeneous microstructure and finer grain sine, thermal、mechanical and electrical properties of the W-l0Cu MIM parts are close or better than those made by Cu infiltration.