Wood's metal, also known as Lipowitz's alloy or by the commercial names Cerrobend, Bendalloy, Pewtalloy and MCP 158, is a fusible metal alloy (having a low melting point) that is useful for

soldering Soldering (; ) is a process of joining two metal surfaces together using a filler metal called solder. The soldering process involves heating the surfaces to be joined and melting the solder, which is then allowed to cool and solidify, creatin ...

and making custom metal parts. The alloy is named for Barnabas Wood, who invented and patented the alloy in 1860. It is a

eutectic alloy A eutectic system or eutectic mixture ( ) is a type of a homogeneous mixture that has a melting point lower than those of the constituents. The lowest possible melting point over all of the mixing ratios of the constituents is called the ''eut ...

of 50%

bismuth Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...

, 26.7%

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

, 13.3%

tin Tin is a chemical element; it has symbol Sn () and atomic number 50. A silvery-colored metal, tin is soft enough to be cut with little force, and a bar of tin can be bent by hand with little effort. When bent, a bar of tin makes a sound, the ...

, and 10%

cadmium Cadmium is a chemical element; it has chemical symbol, symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12 element, group 12, zinc and mercury (element), mercury. Like z ...

by mass. It has a

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...

of approximately . Its fumes are toxic, as well as being toxic on skin exposure.

Applications

Wood's metal is used for making fusible links in the sprinkler heads of commercial building automatic

fire sprinkler system A fire sprinkler system is an active fire protection method, consisting of a water supply system providing adequate pressure and flowrate to a water distribution piping system, to which fire sprinklers are connected. Although initially used on ...

s. Due to the fire, ambient temperature increases enough to melt the link, releasing the water. A similar use is fusible plugs in boilers. Uses also include making custom-shaped apertures and blocks (for example, electron-beam cutouts and lung blocks) for medical radiation treatment, and making casts of keys that are hard to otherwise duplicate. Like other fusible alloys, e.g. Rose's metal, Wood's metal can be used as a heat-transfer medium in hot baths. Hot baths with Rose's and Wood's metals are not used routinely but are employed at temperatures above . At room temperature, Wood's metal has a

modulus of elasticity An elastic modulus (also known as modulus of elasticity (MOE)) is a quantity that describes an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. Definition The elastic modu ...

of 12.7 GPa and a

yield strength In materials science and engineering, the yield point is the point on a stress–strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and w ...

of 26.2 MPa.

Toxicity

Wood's metal is toxic because it contains lead and cadmium, and contamination of bare skin is considered harmful. Vapour from cadmium-containing alloys is also known to pose a danger to humans.

Cadmium poisoning Cadmium is a naturally occurring toxic metal with common exposure in industrial workplaces, plant soils, and from smoking. Due to its low permissible exposure in humans, overexposure may occur even in situations where only trace quantities of ca ...

carries the risk of

cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

anosmia Anosmia, also known as smell blindness, is the lack of ability to detect one or more smells. Anosmia may be temporary or permanent. It differs from hyposmia, which is a decreased sensitivity to some or all smells. Anosmia can be categorized int ...

(loss of sense of smell), and damage to the liver, kidneys, nerves, bones, and respiratory system. Field's metal is a non-toxic alternative. The dust may form flammable mixtures with air.

Related alloys

References

Bibliography

* ''Birchon's Dictionary of Metallurgy'', London, 1965 * ''Experimental techniques in low-temperature physics'', G. K. White, Oxford University Press, Third Edition

External links

* Making your own low-melting point eutectic:
Science Toys: A metal that melts in hot water
'
Burdakin ''et al.'', "Melting points of gallium and of binary eutectics with gallium", ''Metrologia'', 2008
* {{authority control fusible alloys Bismuth alloys Tin alloys Cadmium alloys Lead alloys