Large Size Tungsten Copper Alloy Preparation by Powder Coating Thermal Deformation

Tungsten copper alloys have been widely used in large capacity vacuum circuit breakers and microelectronics due to their excellent properties. Tungsten and copper are mainly used in electrical materials, including electrical contact materials and electrode materials. Tungsten copper alloy sheet has been used in power electronic devices as a new type of electronic packaging material due to its small expansion coefficient and good conductivity and thermal conductivity.

In recent years, the powder-coated hot deformation method has been developed to increase the relative density (>98%) of W-Cu alloys, with fine grain structure, high hardness and good conductivity. However, there are some limitations in hot extrusion: firstly, it is difficult to obtain large-sized wide and thin tungsten-copper plates due to the limitation of extrusion process; secondly, the tungsten copper alloy is hot deformed at 800-1000 ℃, because the heating temperature is below the copper melting point (1083 ℃), the copper phase is still in solid state, the fluidity and filling pore properties are poor, and segregation and macropore are prone to occur. At the same time, tungsten phase growth will greatly reduce the hardness of the material during sintering process. Therefore, there is still room for improvement in the thermal deformation method of powder coating. Some scholars have upgraded the scheme accordingly. The contents of preparation and upgrade are as follows:

According to the quality ratio of tungsten powder to copper powder of 30:70, tungsten powder diameter of 1.2 um, copper powder diameter of 50 um, ball milling speed of 150 rpm and ball milling time of 2.5 h, the mixed powder was molded into 400 mm *200 mm *10 mm tungsten-copper cold-pressing slab under 600 MPa, and the tungsten-copper cold-pressing slab was coated with 5 mm low carbon steel sleeve, heated to 1100 ℃ with heating rate of 30 min, and kept warm for 30 min, and several times on the mill of 400 *400 mm. Tungsten-copper sheet was obtained by hot rolling. The density, conductivity and hardness of the W-Cu sheet are 99.3%, 82% IACS and 95HV respectively.

The principle of the above-mentioned method is that the tungsten-copper powder cold-compacted blank is wrapped without sintering and directly deformed at the temperature near the melting point of copper. The fluidity of copper phase and the filling property of pore can be greatly improved by utilizing the transient liquid phase effect produced by the copper phase temperature approaching or exceeding its own melting point in the process of high temperature deformation. This scheme provides a low-cost and large-scale production process for the preparation of large-size tungsten-copper sheets with high performance. By rolling at temperatures beyond the melting point of copper, filling the pore adequately through the rapid flow of liquid copper under rolling pressure, and forming a complete conductive copper network, tungsten copper alloy sheets with close compactness, high hardness and good conductive and thermal properties can be obtained.

• < Prev
• Next >