A fusible alloy is a

metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...

alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys. Sometimes the term "fusible alloy" is used to describe alloys with 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 ...

below . Fusible alloys in this sense are used for

solder Solder (; North American English, NA: ) is a fusible alloy, fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces aft ...

Introduction

Fusible alloys are typically made from low melting metals. There are 14 low melting metallic elements that are stable for practical handling. These are in 2 distinct groups: The 5 alkali metals have 1 s electron and melt between +181 (Li) and +28 (Cs) Celsius; The 9 poor metals have 10 d electrons and from none (Zn, Cd, Hg) to three (Bi) p electrons, they melt between -38 (Hg) and +419 (Zn) Celsius. From a practical view, low-melting

s can be divided into the following categories: * Mercury-containing alloys *Only

alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...

-containing alloys *

Gallium Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, elemental gallium is a soft, silvery metal at standard temperature and pressure. ...

-containing alloys (but neither alkali metal nor mercury) *Only

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 ...

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 ...

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 ...

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 ...

zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...

indium Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...

, and sometimes

thallium Thallium is a chemical element; it has Symbol (chemistry), symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Che ...

-containing alloys *Other alloys (rarely used) A practical reason here is that the chemical behaviour of alkali metals is very distinct from poor metals. Of the 9 poor metals Hg (mp -38 C) and Ga (mp +29 C) have each their distinct practical issues, and the remaining 7 poor metals from In (mp +156 C) to Zn (mp +419 C) can be viewed together. Of elements which might be viewed as related but do not share the distinct properties of poor metals: Po is estimated to melt at 254 C and might be poor metal by properties but is too radioactive (longest halflife 125 years) for practical use; At same reasoning as Po; Sb melts at 630 C and is regarded as semimetal rather than poor metal; Te is also regarded as semimetal not poor metal; of other metals, next lowest melting point is Pu, but its melting point at 640 Celsius leaves a 220 degree gap between Zn and Pu, thus making the "poor metals" from In to Zn a natural group. Some reasonably well-known fusible alloys are

Wood's metal 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 and making custom metal parts. The alloy is n ...

Field's metal Field's metal, also known as Field's alloy, is a fusible alloy that becomes liquid at approximately . It is named after its inventor, Simon Quellen Field. It is a eutectic alloy of bismuth, indium, and tin, with the following mass fractions: ...

, Rose metal,

Galinstan Galinstan is a brand name for an alloy composed of gallium, indium, and tin which melts at and is thus liquid at room temperature. In scientific literature, galinstan is also used to denote the eutectic alloy of gallium, indium, and tin, which ...

, and NaK.

Applications

Melted fusible alloys can be used as

coolant A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corr ...

s as they are stable under heating and can give much higher thermal conductivity than most other coolants; particularly with alloys made with a high

thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...

metal such as

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

. Metals with low

neutron cross-section In nuclear physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. The neutron cross section σ can be defined as the area in cm2 for which the number of ...

are used for cooling

nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...

s. Such alloys are used for making the fusible plugs inserted in the furnace crowns of

steam boiler file:Dampfkessel für eine Stationärdampfmaschine im Textilmuseum Bocholt.jpg, An industrial boiler, originally used for supplying steam to a stationary steam engine A boiler or steam generator is a device used to create steam by applying heat ...

s, as a safeguard in the event of the water level being allowed to fall too low. When this happens the plug, being no longer covered with water, is heated to such a temperature that it melts and allows the contents of the boiler to escape into the furnace. In automatic

fire sprinkler A fire sprinkler or sprinkler head is the component of a fire sprinkler system that discharges water when the effects of a fire have been detected, such as when a predetermined temperature has been exceeded. Fire sprinklers are extensively used ...

s the orifices of each sprinkler is closed with a plug that is held in place by fusible metal, which melts and liberates the water when, owing to an outbreak of fire in the room, the temperature rises above a predetermined limit. Bismuth on solidification expands by about 3.3% by volume. Alloys with at least half of bismuth display this property too. This can be used for mounting of small parts, e.g. for machining, as they will be tightly held.

Low-melting alloys and metallic elements

Well-known alloys

Other alloys

Starting with a table of component elements and selected binary and multiple systems ordered by melting point: Then organized by practical group and alphabetic symbols of components: Most of the pairwise phase diagrams of 2 component metal systems have data available for analysis, like at https://himikatus.ru/art/phase-diagr1/diagrams.php Taking the pairwise alloys of the 7 poor metals other than Hg and Ga, and ordering the pairs (total 21) by alphabetic of these elements Bi, Cd, In, Pb, Sn, Tl, Zn are as follows: *Bi-Cd https://himikatus.ru/art/phase-diagr1/Bi-Cd.php simple eutectic (Bi at 271 C, Cd at 321, eutectic at 146) *Bi-In https://himikatus.ru/art/phase-diagr1/Bi-In.php has ordered phases, eutectic at +72 - in table above *Bi-Pb https://himikatus.ru/art/phase-diagr1/Bi-Pb.php eutectic at +125 - in table above *Bi-Sn https://himikatus.ru/art/phase-diagr1/Bi-Sn.php eutectic at +139 - in table above *Bi-Tl https://himikatus.ru/art/phase-diagr1/Bi-Tl.php an intermetallic alloy and the lower melting eutectic at +188 *Bi-Zn https://himikatus.ru/art/phase-diagr1/Bi-Zn.php eutectic at +255 *Cd-In https://himikatus.ru/art/phase-diagr1/Cd-In.php eutectic at +128 *Cd-Pb https://himikatus.ru/art/phase-diagr1/Cd-Pb.php eutectic at +248 *Cd-Sn https://himikatus.ru/art/phase-diagr1/Cd-Sn.php eutectic at +176 *Cd-Tl https://himikatus.ru/art/phase-diagr1/Cd-Tl.php eutectic at +204 *Cd-Zn https://himikatus.ru/art/phase-diagr1/Cd-Zn.php eutectic at +266 *In-Pb https://himikatus.ru/art/phase-diagr1/In-Pb.php is NOT eutectic because Pb solid solution in In only raises melting point *In-Sn https://himikatus.ru/art/phase-diagr1/In-Sn.php eutectic at +120 *In-Tl https://himikatus.ru/art/phase-diagr1/In-Tl.php also NOT eutectic because Tl solid solution in In raises melting point *In-Zn https://himikatus.ru/art/phase-diagr1/In-Zn.php eutectic at +143 *Pb-Sn https://himikatus.ru/art/phase-diagr1/Pb-Sn.php eutectic at +183 - in table above *Pb-Tl https://himikatus.ru/art/phase-diagr1/Pb-Tl.php also NOT eutectic because the solid solution is higher melting than components *Pb-Zn https://himikatus.ru/art/phase-diagr1/Pb-Zn.php eutectic at +318 *Sn-Tl https://himikatus.ru/art/phase-diagr1/Sn-Tl.php eutectic at +168 *Sn-Zn https://himikatus.ru/art/phase-diagr1/Sn-Zn.php eutectic at +198 - in table above *Tl-Zn https://himikatus.ru/art/phase-diagr1/Tl-Zn.php eutectic at +292 Considering the binary systems between alkali metals: Li only has appreciable solubility in pair *Li-Na https://himikatus.ru/art/phase-diagr1/Li-Na.php eutectic at +92 The other three alkali metals: *K-Li https://himikatus.ru/art/phase-diagr1/K-Li.php *Li-Rb https://himikatus.ru/art/phase-diagr1/Li-Rb.php *Cs-Li https://himikatus.ru/art/phase-diagr1/Cs-Li.php practically do not dissolve Li even when liquid and therefore their melting points are not lowered by presence of Li Na is in liquid phase miscible with all three heavier alkali metals, but on freezing forms intermetallic compounds and eutectics: *K-Na https://himikatus.ru/art/phase-diagr1/K-Na.php eutectic at -12,6 - in table above *Na-Rb https://himikatus.ru/art/phase-diagr1/Na-Rb.php eutectic at -4,5 *Cs-Na https://himikatus.ru/art/phase-diagr1/Cs-Na.php eutectic at -31,8 The 3 binary systems between the three heavier alkali metals are all miscible in solid at melting point, but all form poor solid solutions that have melting point minima. This is distinct from eutectic: at eutectic point, two solid phases coexist, and close to eutectic point, the liquidus temperature rises rapidly as just one separates, whereas at poor solid solution melting point minimum, there is a single solid phase, and away from the minimum the liquidus temperature rises only slowly. *K-Rb https://himikatus.ru/art/phase-diagr1/K-Rb.php solid solution minimum mp +34 *Cs-K https://himikatus.ru/art/phase-diagr1/Cs-K.php solid solution minimum mp -38 - in table above *Cs-Rb https://himikatus.ru/art/phase-diagr1/Cs-Rb.php solid solution minimum mp +10

References

External links

Fusible (Low Temp) Alloys
Archived fro

on 2012-10-12.
Jenson, W.B. "Ask the Historian - Onion's fusible alloy"
{{Webarchive, url=https://web.archive.org/web/20160304023444/http://www.che.uc.edu/Jensen/W.%20B.%20Jensen/Reprints/178.%20Fusible%20Alloys.pdf , date=2016-03-04 Coolants