The Preparation Of Copper-tungsten Nanocomposite And The Discussional Research Into Its Composing Mechanics

The copper-tungsten nanocomposite is a king of "artificial alloy" composed by tungsten with high melting point and degree of hardness and copper with high electricity and thermal conduction. Because of its resistance against electric arc erosion and fusion welding and its high degree of hardness and intensity, it is widely used with electric contacting material, electric resistance welding, electric spark manufacture, plasma electric pole material, electrothermal alloy and high density alloy, special lathe-hand material (such as air spout in rocket, throat-substrate in plane), central processing system in computer, leading wire frame in large scale compound integration, solid-stated microwave tube, etc. With the rapid development of science, all kinds of applications in reality require higher and higher performance on copper-tungsten nanocomposite. The materials made by copper-tungsten nanocomposite powders possess extremely high density (even nearly fully dense) and so much high conduction of electricity and thermal which the normal materials can not possess. So the essential point of this research is researching key manufacture technologies and manufacturing much better W-Cu composite than normal material in performance and requirement aspects.This research illustrates as the W-15Cu, selects the best manufacturing way forit, discussional researches into its composing mechanics and optimizes its processing or controlling parameter. This research composes the nano-copper powder which has very good industrialization prospect and is manufactured by direct current plasma evaporating-coacervating way with nano-tungsten powder which is multitudinously manufactured by reduction method in industry. The research uses so mature heating pressing-liquid phase sintering method by which the high equality and good organiza -tion with close grain can be manufactured. The specific contents are listed as the following several parts:This thesis simply discusses the process and fundamentals that the nano -copper powder is manufactured by direct current plasma evaporating-coacervating way, describes the whole process that the spherical homogeneous dispersed nano- copper powder (average particle size is 100 nanometer) is manufactured through appropriate processing parameter. This thesis researches the pattern of the nano -copper powder and the both components' relative distributions in W-Cu composite powers, and analyzes how the particle size, degree of fineness, degree of homogene- ity and the collocation of the composite powders effect the manufacturing process and the alloy's performance. This thesis simply researches the non-homogeneous pheno -menon of the pressed compact and fairly deep researches the relationship between the pressure and the density in normal or heat pressing processes. This thesis is divided into three parts to discussionally research the densification process of the copper-tungsten composite and the growth mechanics of the sintering-neck. This thesis discussionally research what the sintering body has happened, such as the reversion, recrystallization, the flowing of the liquid phase, the solvency-separation of the solid phase and the growth of the grains, etc. This thesis as well researches the phenomena of the abnormal growth of the grains, the dissipation of the copper, and the distribution of the extraneous components. Trough a series of sintering trials and the discussionally researches of the sintering process, this thesis summarizes the best technological parameters of the manufacturing process of copper-tungsten nanocomp- osite in heating pressing-liquid phase sintering method.The research has found that the sample's density follows the increment of the pressure and both the parameters nearly accord with the double-logarithm equation. The sintering process of copper-tungsten nanocomposite powders is mainly the liquid phase sintering process, and is also the important processes of the tungsten grain's growth and shift and the copper phase's shift. The growth of the sintering-neck is by the following three manners: surface diffusion, grain boundary diffusion and capacity diffusion. The manner of the tungsten grain's growth is tentatively determined as the merging-growth way. The excessive high temperature or heating-up velocity can lead into the abnormal growth of the grains. The extraneous components in the sample's organizations mainly gather into the big hole which can not contract completely. In the end, through the researches into the mentioned above, the trail obtains nearly completely dense copper-tungsten nanocomposite in the best processing parameters. Its density attains to 15.94 g/cm3, and its Vicker's diamond hardness attains to 310~ 340 which is much more than 0.12 times as the latest copper-tungsten alloy in use. This research's main conclusions provide many experimental foundations and bases for the industrialization and widely uses of high quality copper-tungsten nanocompos -ite.