Precious, Refractory, and Specialty Metals

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Chapter 24

• Precious, Refractory, and Specialty Metals

Precious Metals Refractory Metals Specialty
Metals
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• Industrial applications of the precious metals
  utilize the unique properties they exhibit.

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• Pure silver has the lowest electrical resistivity
  of any metal and is an excellent conductor of
  heat.

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• Gold is commonly alloyed with copper and silver
  to increase hardness, increase strength, and
  minimize cost.

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• The platinum group can be divided into three sets
  of twins by the crystal structures and properties
  they exhibit.

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• The recrystallization temperatures of pure metals
  is approximately 40 of their melting
  temperatures.

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• Wrought tantalum alloys have good ductility at
  cryogenic temperatures.

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• Niobium is solid solution hardened by tantalum,
  tungsten, molybdenum, titanium, and zirconium.

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• The major use of molybdenum is as an alloying
  element in steels, cast irons, heat-resistant
  alloys, and corrosion-resistant alloys.

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• An important use of tungsten is as an alloying
  element in steels, high-speed tool steels, and
  nickel-cobalt alloys.

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• The major use of beryllium is as an alloying
  element in copper and nickel to produce
  age-hardening alloys for springs, electrical
  contacts, spot welding electrodes, and
  nonsparking tools.

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• The major use of zirconium is as zircon sand in
  foundries.

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• Most zirconium alloys are dilute alpha alloys and
  consist of alpha phase at room temperature.