Tungsten Copper Liner Warm Flow Compaction

Tungsten copper liner is a kind of psudoalloy that composed of W and Cu, which is immiscible and forming compound with each other. So it is difficult to fabricate by common pressing-sintering process, the most widely used in tungsten copper products is powder metallurgy (PM), which includes infiltration and activated liquid-phase sintering. Infiltration presses tungsten powder into a compact, at a certain temperature pre-sinter the porous tungsten skeleton with density and strength. And then the low melting point of the molten liquid copper is infiltrated tungsten skeleton in order to obtain tungsten copper alloy with fully densified. The main mechanism is the liquid metal wetting porous matrix metal, under the effect of capillary forces along the inter-particle pore liquid copper flows and fills pores of the porous tungsten skeleton.

According to the sintering temperature, infiltration process can be specifically divided into sinter tungsten skeleton at high temperature + Cu infiltrated and sinter composite powder at low temperature + Cu infiltrated. Sinter tungsten skeleton at high temperature + Cu infiltrated presses tungsten powder into a compact before sinter and infiltrated Cu at 1800-2200℃. Since the tungsten powder at a high temperature to fully restore the remaining low-melting impurities and sub-oxides can be restored by evaporation gasification and thermal decomposition was removed, thus prepared tungsten copper shaped relative density of 99.2% comprehensive and excellent performance.

However, it also has some disadvantages, such as long production cycle, the control parameters are many and complex and high production cost. While sinter composite powder at low temperature + Cu infiltrated is mixed with a small amount of induced copper before sintering and infiltration. Generally, induced copper content of about 2.5% -3.5% and the granularity is similar to tungsten powder, which can effectively improve the compacting performance and the flowability of liquid Cu. But too much of the added amount of copper will result in enrichment-induced infiltration of copper, so that the overall the density of tungsten copper liner decreases.

Overall, compared with the injection molding suitable for the smaller components, warm flow compaction is more suitable for the larger components with complex structure and shape. It has higher requirements on the granularity of raw material and is sensitive to the temperature changes and the amounts of binder. Low temperature may cause mixing powder flow properties deteriorated, so that the tungsten copper shaped charge density distribution can not be molded or uneven. High temperature may obviously separate the two phase (the mixed powder and the binder). The excessive amount of adhesive may cause infiltrated tungsten skeleton pore through the large, so that the density decreases and easily deformed. In addition, warm flow compaction combines the advantages of injection molding and warm compacting process, and it can effectively improve the density, the penetration depth and armor capability of tungsten copper liner, which is the ideal choice for tungsten copper liner manufacturing in the future.