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the common name for a group of iron-nickel-base alloys characterized by elastic properties that are virtually unaffected by changes in temperature. The first elinvar was a binary alloy containing 45 percent Ni (the rest being Fe); subsequently, elinvars containing Cr, Mo, and W were developed.
The anomalies in the elastic properties of elinvars are magnetic in their physical nature, and consequently above the Curie point they disappear. The principal reasons for the anomalies are the reduction of the binding forces in the crystal lattice during the transition to the magnetic state and the change in the magnetic domain structure during the deformation of the lattice. The domain structure is secured by means of precipitation hardening, in the course of which one of the following elements is added to the alloy: Ti, Al, Nb, or Be.
Elinvars are used to make springs for watches, ultrasonic delay lines, resonators for electromechanical filters, diaphragms, springs, and other parts requiring that the elastic properties be independent of temperature.