Low Expansion Iron-Nickel Alloy

Iron-nickel alloys demonstrate a very low expansion rate at room temperature. These low thermal expansion alloys have found use in modern applications which require joining of a metal to glass or ceramics and in areas that demand same thermal expansion rates for materials to be joined in order to prevent associated problems within the joint area.

The coefficient of thermal expansion of nickel and iron is more or less the same. However, adding nickel to iron can result in an alloy with a reduced coefficient of thermal expansion by an order of magnitude. These characteristics make them suitable for use in a myriad of applications, including medical, electronics, aerospace engineering, telecommunications and cryogenic components.

Alloy 42 (K94100/ASTM F30)

Alloy 42 is a binary nickel-iron alloy consisting of ~41% nickel. This material demonstrates low and typically consistent thermal expansion characteristics over a wide temperature range of 20-300 °C. Its coefficient of thermal expansion is matched to materials such as silicon, beryllia, alumina and vitreous glass compounds. This characteristic makes it suitable for tooling for aerospace composites and glass-to-metal and ceramic sealing applications.

Properties of Alloy 42

The following are the typical physical properties of Alloy 42:

Coefficient of thermal expansion: 4.0-4.7 at 30-300 °C; 6.7-7.4 at 30-450 °C
Density: 8.15 g/cm3
Melting point: 1425 °C
Curie point: 330 °C
Thermal conductivity: 12.5 W/m°C
Specific heat: 0.5 J/g.°C
Young's modulus (MPa): 145,000

Applications of Alloy 42

Alloy 42 is used as a sealing material in electric industrial lamps, vacuum devices, thermostat rods, microelectronic components, CRT electron guns, electronic tubes, and semiconductor packages.

This information has been sourced, reviewed and adapted from materials provided by Columbia Metals.

For more information on this source, please visit Columbia Metals.

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