7. Various alloys

7.1 Low-melting metals and alloys

Tin and lead are the reference metals for low-melting alloys.

• Pewter

  At the limit of the metals in the periodic table, tin is a semi-metal, which explains its low melting point (T _f = 232°C), its double crystalline structure: face-centered tetragonal ("gray" tin, density 5.8, at T < 18°C) and cubic ("white" tin, density 7.3, at T > 18°C).

  Its good corrosion resistance and high malleability have justified its centuries-old use in household instruments.

  The change in crystalline structure at 18°C, which is accompanied by strong contraction leading to pulverization ("tin plague"),...