About research on tungsten copper composite materials
Tungsten-copper composite materials have high electrical and thermal conductivity, low expansion coefficient, good high-temperature strength and arc ablation resistance, and have been widely used in electrical engineering, mechanical processing, electronic information and other fields. This paper introduces the traditional process and new preparation technology of tungsten-copper composite materials, reviews its applications in the fields of electrical switches, electrodes, microelectronics and military industry, and prospects its preparation technology and application development.
Preface
The research and development of tungsten-copper composite materials can be traced back to the 1930s. Due to its good voltage resistance and resistance to electrical ablation, it was widely used in industrial sectors such as high-voltage electrical switches. In the 1960s, tungsten-copper composite materials gradually found applications in fields such as resistance welding electrodes and aerospace high-temperature resistant components. Since then, with the gradual improvement of preparation technology and the continuous expansion of application fields, the development and application of tungsten-copper composite materials have gradually matured. In the 1990s, as electronic packaging and heat sink materials, they began to be used in large-scale integrated circuits and high-power applications. Electronic devices and other fields have received widespread attention. Entering the 21st century, tungsten-copper composite materials have been used in military and high-tech fields as armor-piercing ammunition cover materials, missile nozzle materials and target materials [1].
Tungsten-copper composite materials are composed of tungsten with high melting point, high density and low expansion coefficient and copper with high electrical and thermal conductivity. It has the superior properties of both and is widely used in industrial sectors such as electronics, electrical appliances, machinery and aerospace [2 ~ 4], has broad application prospects in many high-tech fields. However, there is a large gap between the melting points of tungsten and copper and they are incompatible with each other. The density of tungsten-copper composite materials prepared by powder metallurgy is not high, which usually results in insufficient electrical conductivity, thermal conductivity and mechanical properties of the material. In order to continuously meet the new requirements put forward by industrial development, The preparation technology and application development of tungsten-copper composite materials have experienced a series of complex development processes.
1. Preparation technology of tungsten-copper composite materials
1.1 Infiltration method
The infiltration method is to press tungsten powder or a mixture of tungsten powder and a small amount of copper powder into a billet, and prepare a porous tungsten skeleton through pre-sintering at a certain temperature, and then melt the metallic copper and use capillary force to make it flow along the gaps between tungsten particles. The skeleton is gradually filled to obtain a tungsten-copper composite material [5]. Since the pore connectivity and size consistency of the tungsten skeleton are difficult to control, it is difficult to ensure the uniform distribution of the copper phase after infiltration, and the copper-rich skin after infiltration must be processed later, which is not conducive to the manufacture of parts with complex shapes [ 6～8]. However, as one of the widely used traditional methods for preparing tungsten-copper composite materials, the materials prepared by the solution infiltration method have the advantages of high density, good sintering performance, and ideal electrical and thermal conductivity.
1. 2 High temperature liquid phase sintering method
The high-temperature liquid phase sintering method mixes and shapes a certain proportion of tungsten powder and copper powder, and sinters them at a temperature above the melting point of copper to obtain a tungsten-copper composite material. Due to the poor surface wettability of liquid copper and tungsten, the sintering densification process of tungsten-copper composite materials prepared using this process is mainly particle rearrangement, which affects the sintering density of the final material. However, as one of the traditional preparation methods of tungsten-copper composite materials, the high-temperature liquid phase sintering method has the advantages of simple production process, easy operation and control [9, 10].
1. 3 Activated liquid phase sintering method
The activated liquid phase sintering method refers to adding trace amounts of Pd, Ni, Co, Fe and other activation elements during the high-temperature liquid phase sintering process to prepare tungsten-copper composite materials to improve the sintering effect and obtain tungsten-copper composite materials. Since the addition of activation elements will affect the electrical and thermal conductivity of the material to varying degrees, it is not conducive to its application in thermal, electrical control and other materials.
