Alperm (alsoalfenol oralfer) is a class ofalloys comprising 83-90% ofiron and 10-17% ofaluminium. The most widely used composition is with 16% Al.[1]
An alloy with 13% Al is also sometimes referred to asalfer. It exhibits largemagnetostriction and it is used in magnetoelastic sensors. Later during the WW2, Japanese used the alloy with 12.7-12.9% aluminium as a replacement ofnickel for the magnetostrictive transducers used in their Type 93 model 5, Type 3, and Simple navalsonars.[2]
Alperm ismagnetically soft and exhibits highmagnetic permeability. The material can be produced in 0.5 mm thick sheets, as well as 50-60 μm thick ribbons.[3]
Thecoercivity is usually below 5 A/m (for alfer it is around 50 A/m) and permeability 55 000 (for alfer 4000). Saturation flux density is 0.8 T (for alfer 1.28 T).
The addition of Al increases electricalresistivity of alloy up to 140 μΩm, which is almost four times the value in commonly used 3% SiFeelectrical steel. For this reason alperm can be used in higher frequency range. However, because of the Al content the material is more susceptible tooxidation.
The alloy was first synthesized and characterized byJapanese researchers H. Masumoto and Hideo Saito in 1939.
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