nickeliron

Nickel-iron is a family of alloys composed primarily of nickel and iron. The two elements are highly soluble in each other, allowing a wide range of compositions from roughly 20 to 80 percent nickel by weight, with the balance iron. These alloys are ferromagnetic at room temperature and can be heat treated and mechanically worked to tailor magnetic, thermal, and mechanical properties for different applications.

Among the best-known grades are Invar, a Fe-Ni alloy typically around 36 percent nickel, which exhibits an unusually low coefficient of thermal expansion and is used in precision instruments and clock mechanisms. Other important grades include Permalloy, which is rich in nickel (about 80 percent) and exhibits very high magnetic permeability and low coercivity, making it valuable for transformer cores and magnetic sensors. Related high-permeability alloys, such as mu-metal and similar compositions, are widely used for magnetic shielding.

Key properties of nickel-iron alloys include soft magnetic behavior, high permeability, and low coercivity in many grades, along with good ductility and corrosion resistance. Some compositions are optimized for minimal magnetostriction, and Invar-type alloys offer excellent dimensional stability over temperature. The magnetic and thermal characteristics can vary significantly with composition and heat treatment.

Processing typically involves melting and alloying followed by annealing or other heat treatments to relieve stress and optimize magnetic performance. Common applications include electrical transformer cores, inductors, magnetic shielding, sensors, precision instruments, and, in some cases, components requiring stable dimensions over temperature.