Copper-tungsten
Encyclopedia
Copper-tungsten 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
s. 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.
The CuW75 alloy, with 75% of tungsten, is widely used in chip carrier
s, substrates, flanges and frames for power semiconductor device
s. The high thermal conductivity of copper together with the low thermal expansion of tungsten allows thermal expansion matching to silicon
, gallium arsenide, and some ceramic
s. 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 charge
s. 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. 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.
For different application should choice the different grade copper tugnsten 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.
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
is a pseudo-alloy of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
and tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
. 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
Microstructure
Microstructure is defined as the structure of a prepared surface or thin foil of material as revealed by a microscope above 25× magnification...
is therefore rather a metal matrix composite
Metal matrix composite
A metal matrix composite is composite material with at least two constituent parts, one being a metal. The other material may be a different metal or another material, such as a ceramic or organic compound. When at least three materials are present, it is called a hybrid composite...
than a true alloy.
The alloy combines the properties of both metals, resulting in a material that is heat-resistant, ablation
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
-resistant, highly thermally
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
and electrically conductive, and easy to machine
Machining
Conventional machining is a form of subtractive manufacturing, in which a collection of material-working processes utilizing power-driven machine tools, such as saws, lathes, milling machines, and drill presses, are used with a sharp cutting tool to physical remove material to achieve a desired...
.
Parts are made from the CuW alloy by pressing the tungsten particles into a desired shape, sintering
Sintering
Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature...
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 |
Applications
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 sinkHeat sink
A heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator in a car...
s. As contact material the alloy is resistant to erosion by electric arc. WCu alloys are also used in electrodes for electrical discharge machining
Electrical discharge machining
Electric discharge machining , sometimes colloquially also referred to as spark machining, spark eroding, burning, die sinking or wire erosion, is a manufacturing process whereby a desired shape is obtained using electrical discharges...
and electrochemical machining.
The CuW75 alloy, with 75% of tungsten, is widely used in chip carrier
Chip carrier
A chip carrier, also known as a chip container or chip package, is a container for a transistor or an integrated circuit. The carrier usually provides metal leads, or "pins", which are sturdy enough to electrically and mechanically connect the fragile chip to a circuit board. This connection may be...
s, substrates, flanges and frames for power semiconductor device
Power semiconductor device
Power semiconductor devices are semiconductor devices used as switches or rectifiers in power electronic circuits . They are also called power devices or when used in integrated circuits, called power ICs....
s. The high thermal conductivity of copper together with the low thermal expansion of tungsten allows thermal expansion matching to silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, gallium arsenide, and some ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
s. Other materials for this applications are CuMo alloy, AlSiC
AlSiC
AlSiC, pronounced "alsick", is a metal matrix composite consisting of aluminium matrix with silicon carbide particles. It has high thermal conductivity , and its thermal expansion can be adjusted to match other materials, e.g. silicon and gallium arsenide chips and various ceramics...
, and Dymalloy
Dymalloy
Dymalloy is a metal matrix composite consisting of 20% copper and 80% silver alloy matrix with type I diamond. It has very high thermal conductivity of 420 W/, and its thermal expansion can be adjusted to match other materials, e.g. silicon and gallium arsenide chips...
.
Alloy with 70-90% of tungsten is used in liners of some specialty shaped charge
Shaped charge
A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, to initiate nuclear weapons, to penetrate armor, and in the oil and gas industry...
s. 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. 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
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
can be added as lubricant to the powder.
For different application should choice the different grade copper tugnsten 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.