Copper-tungsten (tungsten-copper, CuW, or WCu) alloy is a pseudo-alloy of copper and tungsten. As copper and tungsten are not mutually soluble, the material is composed of distinct particles of one metal dispersed in a matrix of the other one. The microstructure is therefore rather a metal matrix composite than a true alloy.
The alloy combines the properties of both metals, resulting in a material that is heat-resistant, ablation-resistant, highly thermally and electrically conductive, and easy to machine.
Parts are made from the CuW alloy by pressing the tungsten particles into a desired shape, sintering the compacted part, then infiltrating with molten copper. Sheets, rods and bars of the alloy are available as well.
Commonly used copper tungsten alloy contains 10 to 50 wt. % of copper, the remaining portion being substantially all tungsten. The typical properties of the alloy depend on its composition. The alloy with less wt.% of copper has higher density, higher hardness and higher resistivity. The typical density of CuW90 alloy, with 10% of copper, is 16.75g/cm3 and 11.85g/cm3 for CuW50 alloy. CuW90 has higher hardness and resistivity of 260 HB kgf/mm2 and 6.5 µΩ.cm than CuW50.
Typical Properties of Commonly Used Copper Tungsten Composition
| Composition | Density | Hardness | Resistivity | IACS | Bending Strength |
|---|---|---|---|---|---|
| wt. % | g/cm3≥ | HB Kgf/mm2≥ | µΩ.cm≤ | %≥ | Mpa≥ |
| W50/Cu50 | 11.85 | 115 | 3.2 | 54 | -- |
| W55/Cu45 | 12.30 | 125 | 3.5 | 49 | -- |
| W60/Cu40 | 12.75 | 140 | 3.7 | 47 | -- |
| W65/Cu35 | 13.30 | 155 | 3.9 | 44 | -- |
| W70/Cu30 | 13.80 | 175 | 4.1 | 42 | 790 |
| W75/Cu25 | 14.50 | 195 | 4.5 | 38 | 885 |
| W80/Cu20 | 15.15 | 220 | 5.0 | 34 | 980 |
| W85/Cu15 | 15.90 | 240 | 5.7 | 30 | 1080 |
| W90/Cu10 | 16.75 | 260 | 6.5 | 27 | 1160 |
CuW alloys are used where the combination of high heat resistance, high electrical and/or thermal conductivity, and low thermal expansion are needed. Some of the applications are in electric resistance welding, as electrical contacts, and as heat sinks. As contact material the alloy is resistant to erosion by electric arc. WCu alloys are also used in electrodes for electrical discharge machining and electrochemical machining.[2]
The CuW75 alloy, with 75% of tungsten, is widely used in chip carriers, substrates, flanges and frames for power semiconductor devices. The high thermal conductivity of copper together with the low thermal expansion of tungsten allows thermal expansion matching to silicon, gallium arsenide, and some ceramics. Other materials for this applications are CuMo alloy, AlSiC, and Dymalloy.
Alloy with 70-90% of tungsten is used in liners of some specialty shaped charges. The penetration is enhanced by factor 1.3 against copper for homogeneous steel target, as both the density and the break-up time are increased.[3] Tungsten powder based shaped charge liners are especially suitable for oil well completion. Other ductile metals can be used as binder in place of copper as well. Graphite can be added as lubricant to the powder.[4]
For different application should choice the different grade copper tungsten composition. The key factor is evaluate the hardness, electrical conductivity. thread tapping is better use the CuW(72% by weight)tungsten composition. for some EDM electrode since it need to be maching after periode of using. the W-70% to 75% composition is recommended.[5]