Low Expansion, Magnetic & Shape Memory Alloys

Some nickel alloys are selected for their special physical properties.  The iron-36% nickel alloy is unique in having almost zero coefficient of thermal expansion around room temperature.  The first application was for pendulums of high precision clocks.  Today, the largest application is for liquefied natural gas (LNG) tanks.  Other alloys in the same family can have their expansion coefficients tailored to match the expansion of the plastics used to encapsulate integrated circuits.

Nickel-iron alloys can also have very high magnetic permeability, making them suitable for shielding electronic equipment from electromagnetic interference.  Permanent magnets based on aluminium-nickel-cobalt-iron were widely used but have been superseded in many applications by ferrites and rare-earth magnets.

55% Nickel-titanium alloys have shape memory properties: if formed at one temperature and then deformed at a lower temperature, they regain their original form when heated up again.  The transition temperatures can be adjusted by careful control of the composition.  Medical devices and specialised connectors are just two of the applications.  The same alloys can also undergo considerable elastic deformation and still return to their original shape super-elastic alloys).  This has been exploited for spectacle frames and shock absorbers to provide earthquake resistance for historic stone buildings.  Properties can be found in manufacturers’ brochures.