Fusible alloy

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A fusible alloy is a metal alloy 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 below 150 °C (302 °F). Fusible alloys in this sense are used for solder.

Introduction[edit]

From practical view, low melting alloys can be divided up into:

  • Mercury-containing alloys
  • Only alkali metal-containing alloys
  • Gallium-containing alloys (but neither alkali metal nor mercury)
  • Only bismuth, lead, tin, cadmium, zinc, indium and sometimes thallium-containing alloys
  • Other alloys (rarely used)

Some reasonably well known fusible alloys are Wood's metal, Field's metal, Rose metal, Galinstan, and NaK.

Applications[edit]

Melted fusible alloys can be used as coolants 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 metal such as indium or sodium. Metals with low neutron cross-section are used for cooling nuclear reactors.

Such alloys are used for making the fusible plugs inserted in the furnace crowns of steam boilers, 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 sprinklers 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.[1]

Low melting alloys and metallic elements[edit]

Low melting alloys and metallic elements
Composition in weight-percent °C eutectic? Name or remark
Cs 73.71, K 22.14, Na 4.14 [2] −78.2 yes
Hg 91.5, Tl 8.5 −58 yes used in low readings thermometers
Hg 100 −38.8 (yes)
Cs 77.0, K 23.0 −37.5
Ga 68.5, In 21.5, Sn 10 −19 no Galinstan
K 76.7, Na 23.3 −12.7 yes
K 78.0, Na 22.0 −11 no NaK
Ga 61, In 25, Sn 13, Zn 1 8.5 yes
Ga 62.5, In 21.5, Sn 16.0 10.7 yes
Ga 69.8, In 17.6, Sn 12.5 10.8 no
Ga 75.5, In 24.5 15.7 yes
Cs 100 28.6 (yes)
Ga 100 29.8 (yes)
Rb 100 39.30 (yes)
Bi 40.3, Pb 22.2, In 17.2, Sn 10.7, Cd 8.1, Tl 1.1 41.5 yes
Bi 40.63, Pb 22.1, In 18.1, Sn 10.65, Cd 8.2 46.5
Bi 32.5, In 51.0, Sn 16.5 60.5 yes Field's metal
Bi 49.5, Pb 27.3, Sn 13.1, Cd 10.1 70.9 yes Lipowitz's alloy
Bi 50.0, Pb 25.0, Sn 12.5, Cd 12.5 71 no Wood's metal
In 66.3, Bi 33.7 72 yes
Bi 50, Pb 30, Sn 20, Impurities 92 no Onions' Fusible Alloy[3]
Bi 52.5, Pb 32.0, Sn 15.5 95 yes
Bi 50.0, Pb 31.2, Sn 18.8 97 no Newton's metal
Bi 50.0, Pb 28.0, Sn 22.0 109 no Rose's metal
Bi 56.5, Pb 43.5 125 yes
Bi 58, Sn 42 139 yes
In 100 157 (yes)
Sn 62.3, Pb 37.7 183 yes
Sn 63.0, Pb 37.0 183 no Eutectic solder
Sn 91.0, Zn 9.0 198 yes
Sn 92.0, Zn 8.0 199 no Tin foil
Bi 100 271.5 (yes)
Zn 100 419.5 (yes)

See also[edit]

References[edit]

  1. ^  Chisholm, Hugh, ed. (1911). "Fusible Metal". Encyclopædia Britannica (11th ed.). Cambridge University Press. 
  2. ^ Oshe, Ed. R.W., "Handbook of Thermodynamic and Transport Properties of Alkali Metals", Oxford. UK, Blackwell Scientific Publications Ltd, 1985, p. 987
  3. ^ Jenson, W.B. "Ask the Historian - Onion's fusible alloy", J. Chem. Ed., 2010, 87, 1050-1051.

Further reading[edit]

  • "ASTM B774—Standard Specification for Low Melting Point Alloys". ASTM International. 1900. doi:10.1520/B0774 .
  • Weast, R.C., "CRC Handbook of Chemistry and Physics", 55th ed, CRC Press, Cleveland, 1974, p. F-22

External links[edit]