Powder Granularity Effect on Tungsten Copper Composite Materials

Tungsten copper composite materials not only have advantages of W, such as high hardness, high strength, high density, low coefficient of thermal expansion and excellent wear and corrosion resistance, but also have good plasticity and excellent thermal and electrical conductivity of Cu, which have been widely used in electronic industry, high-temperature resistant devices fields. But there is a big difference in melting point and physical properties between W and Cu, and they are immiscible. So it makes tungsten copper composite material preparation process simpler, commonly used PM (Powder Metallurgy) process, which limits the rang of applications. Therefore, we through analyzing powder granularity effect on the density of tungsten copper composite materials, optimizing the sintering process, the properties will be further promoted.

Take mass ratio of 85% of tungsten copper composite material manufacture as example, the particle size of not more than 1.0μm nano-crystalline copper with particle size of not more than 0.8μm nano-crystalline tungsten powder mass ratio of 85:15 were mixed in a ball mill planetary, milling medium is ethanol. After ball milling, take powder and dried in a vacuum glove box under Ar protection; after drying, pressed and vacuum sintered. Viewed from SEM image, with increasing milling time, the granularity of powder reduced and the degree of mixing and mechanical alloying of the number of particles has been significantly increased. Although tungsten particle has high hardness, sharp edge portion is worn continuously, and shape gradually becomes more regular ball; Copper particles are constantly impact occurs between the ball, the tank and the tungsten particles, grinding and tearing, particle size becomes smaller. So the mutual attraction between particles become greater, the rearrangement faster. In addition, small powder size, large surface area, surface activity and lattice activity also increased, which is beneficial for sintering process and improving the density and structure of tungsten copper composite materials.

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