There are two main Fe-Ni and Fe-Co soft magnetic alloys in general use, depending on the application requirements. Of course, there are several variants for these alloys, but the variants typically use the same annealing specifications as the parent alloy. The alloy of nominal composition Fe-48%Ni is referred to in the industry as High Permeability “49”® (Carpenter Technology), Permenorm® 5000 (Vacuumschmelze GmbH) or Magnifer® 50 (VDM Metals), and is available in various grades and forms. Because of its moderately high permeability and saturation induction of 1.5T, it is widely used for instrument transformers, magnetic shields, oscillators and solenoid cores. A related alloy is the Fe-80%Ni-5%Mo composition historically known as Mu-metal. Depending on the supplier, it is called HyMu “80”® (Carpenter Technology), Magnifer® 7904 (VDM Metals), Ultraperm® 250 (Vacuumschmelze GmbH) or Moly Permalloy (Allegheny Technologies Inc.). This alloy boasts very high permeability, low saturation and low coercivity, making it ideal for use in tape wound toroids, transformer laminations, electromagnetic relays and stepping motors.
The alloy historically called vanadium permendur, is an alloy with a nominal composition of 49%Fe-49%Co-2%V. The alloy is referred to in the industry as Hiperco® 50A (Carpenter Technology) or Vacoflux® 50 (Vacuumschmelze GmbH). This alloy combines very high saturation induction (2.4 T) and high permeability with low coercivity and core loss, making it ideal for use in generators, specialty transformers, magnetic bearings, high magnetic flux devices and as pole pieces in electromagnets. A related alloy has a composition of Fe-27%Co and is known as Hiperco® Alloy 27 (Carpenter Technology) or Vaocoflux® 27. This alloy has high saturation induction and permeability, but also with higher coercivity. However, because it is quite ductile and tough, it is excellent for use in high performance actuator systems, motors, generators, relays and electromagnet pole pieces.