The Fabrication Of W-Cu Nano-crystalline Precursor Composite Powders By Mechanical Alloying

Tungsten is such a metal that combines high strength, high rigidity and high resistance to abrasion and corrosion. Copper has excellent electrical and thermal conductivity. The preparation of W-Cu composites is expected to combine the advantages of two individual metals. Currently, the W-Cu composite materials are widely applied in various industrial fields such as electrical industry and military weapons manufacturing. Generally, the W-Cu composite powders fabricated by conventional methods have poor sinterability. However, when the grain sizes of the powders reduce to the nanometer-scale, the bulk sintered part can achieve a nearly full densification.The process of mechanical alloying (MA) has been an efficient method for fabrication of nano-structured materials from its beginning. The present paper reports the studies on W-Cu nano-structured precursor composite powders prepared by MA. Based on the former studies, the author set some proper parameters. The experimental analyses were made on three different kinds of raw materials. The analyses and investigations were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).First, the experiments were based on the raw materials of W-CuO. The experimental analyses concluded the changes of grain size, morphologies and phases of the powders, and the microstructure. The experiments were carried out at the condition of different milling speed. The results show that the nano-crystalline powders can be obtained faster under the high milling speed and the grain size was smaller. During the milling process, the solid reaction of W-CuO occurred. Through the further experiment for the studies on the mechanism of the reaction, the author found that the reaction was finished in a short time.Based on the results of the experiments of the W-CuO raw materials, the experiments using the WO3-CuO and W-Cu as raw materials were carried out. Then, the experimental results about the three different kinds of raw materials were compared. The results show that there were chemical reactions during the milling of the WO3-CuO and W-Cu powders, finding that the CuWO4 formed in the former while a little amount of WO2 in the latter. The reactive mechanism was the same with the solid reactive mechanism of W-CuO. Through the comparison, it can be gotten conclusion that it is the relative proper choice to use the W-CuO as raw materials for fabrication of W-Cu nano-structured precursor composite powders.