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Fusible alloy

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 183 °C (361 °F; 456 K). Fusible alloys in this sense are used for solder.

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 alloys can be divided into the following categories:

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, Field's metal, Rose metal, Galinstan, and NaK.

Applications

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]

Bismuth on solidification expands by about 3.3% by volume. Alloys with at least half of bismuth display this property too.[2] This can be used for mounting of small parts, e.g. for machining, as they will be tightly held.[citation needed]

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:

Considering the binary systems between alkali metals: Li only has appreciable solubility in pair

The other three alkali metals:

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:

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.

See also

References

  1. ^  One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Fusible Metal". Encyclopædia Britannica. Vol. 11 (11th ed.). Cambridge University Press. p. 369.
  2. ^ "F.A.Q." Archived from the original on 2004-08-07.
  3. ^ Oshe, R.W. (ed.), "Handbook of Thermodynamic and Transport Properties of Alkali Metals", Oxford. UK, Blackwell Scientific Publications Ltd, 1985, p. 987
  4. ^ a b c d e White, Guy Kendall; Meeson, Philip J. (2002). Experimental techniques in low-temperature physics. Clarendon. pp. 207–. ISBN 978-0-19-851428-2.
  5. ^ Johnson Manufacturing Co, MSDS for Chip Quik Alloy w/Lead. Retrieved on February 6, 2015.
  6. ^ "Lens Blocking alloy 136 58oC". Archived from the original on 2016-10-17.
  7. ^ a b c "A Guide to Low Temperature Solder Alloys | Indium Corporation® | Indium Corporation Blogs | Indium | Solder Alloys". indium.com. Retrieved 2022-10-08.
  8. ^ François Cardarelli (2008-03-19). Materials Handbook: A Concise Desktop Reference. Springer Science & Business Media. pp. 210–. ISBN 978-1-84628-669-8.
  9. ^ Jensen, William B. (2010-10-01). "The Origin of the Name "Onion's Fusible Alloy"". Journal of Chemical Education. 87 (10): 1050–1051. Bibcode:2010JChEd..87.1050J. doi:10.1021/ed100764f. ISSN 0021-9584.
  10. ^ a b John H. Lau (1991). Solder joint reliability: theory and applications. Springer. p. 178. ISBN 0-442-00260-2.[permanent dead link]
  11. ^ a b Ray P. Prasad (1997). Surface mount technology: principles and practice. Springer. p. 385. ISBN 0-412-12921-3.
  12. ^ Charles A. Harper (2003). Electronic materials and processes. McGraw-Hill Professional. pp. 5–8. ISBN 0-07-140214-4.
  13. ^ Karl J. Puttlitz, Kathleen A. Stalter (2004). Handbook of lead-free solder technology for microelectronic assemblies. CRC Press. ISBN 0-8247-4870-0.
  14. ^ Qualitek. Technical Data Sheet Sn42/Bi58 Solid Wire Rev.A 03/14 (PDF). Retrieved 3 May 2018.
  15. ^ "Oregon State University". Oregon State University. Retrieved 2022-04-06.
  16. ^ T.Q. Collier (May–Jun 2008). "Choosing the best bumb for the buck". Advanced Packaging. 17 (4): 24. ISSN 1065-0555.
  17. ^ msl747.PDF. (PDF). Retrieved 2010-07-06.
  18. ^ Qualitek. Technical Data Sheet Sn42/Bi58 Solid Wire Rev.A 03/14 (PDF). Retrieved 3 May 2018.
  19. ^ "Tin-Zinc Solders for Aluminium to Aluminium and Copper". Kapp Alloy & Wire, Inc. Archived from the original on 16 July 2013. Retrieved 23 October 2012.
  20. ^ Madara Ogot, Gul Okudan-Kremer (2004). Engineering design: a practical guide. Trafford Publishing. p. 445. ISBN 1-4120-3850-2.
  21. ^ Howard H. Manko (8 February 2001). Solders and soldering: materials, design, production, and analysis for reliable bonding. McGraw-Hill Professional. pp. 396–. ISBN 978-0-07-134417-3. Retrieved 17 April 2011.

Further reading

External links