Tungsten Copper Electrode Sintering Mechanism and Densification

Tungsten copper has been widely used in electrode (EDM or ECM), electronic packaging materials and some fields because of its high density, strength and excellent thermal and electrical conductivity. Due to the large differences physicochemical property between two metals (tungsten and copper), which called binary psudoalloy, tungsten copper uses powder metallurgy (PM) to manufacture replace casting process. It uses tungsten and copper powder with fine grain and high purity, the general process is: powder milling → mixed → compacting → sintering → infiltration → cold working.

This paper concentrates on analyzing the relation between sintering mechanism and densification of tungsten copper material. Generally, the traditional sintering theory said that if a system intend to achieve higher densification, it should has good wettability and the solid phase can dissolve in the liquid phase and proper amount of liquid phase. According to the relationship of tungsten and copper in the process of sintering, the copper-tungsten binary phase diagram can be drew as follow:

The diagram shows that tungsten copper system belongs to completely insoluble system. In addition, the wettability of copper solution is not so well to tungsten skeleton in common conditions. Recently, more and more researchers and scholars find that tungsten copper powder with nano composite structure has better sintering properties. It is due to tungsten copper compacts in solid phase state, although tungsten copper powder with nano composite structure does not dissolve the segregation. They though it is related with one solid phase sintering and liquid particle rearrangement effects.

Except the cementation of powder particle, densification and the change of constituent of pure metal, there is no dissolve and appear new phase in the process of one solid phase sintering. Then we will use the model of tungsten copper pressed compact to show the varieties of powder in the process of solid phase, which will intuitively describe the relation between sintering mechanism and densification of tungsten copper electrode.

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