Permalloy
Permalloy is a nickel-iron magnetic alloy, with about 80% nickel and 20% iron content. Invented in 1914 by physicist Gustav Elmen at Bell Telephone Laboratories, it is notable for its very high magnetic permeability, which makes it useful as a magnetic core material in electrical and electronic equipment, and also in magnetic shielding to block magnetic fields. Commercial permalloy alloys typically have relative permeability of around 100,000, compared to several thousand for ordinary steel.
In addition to high permeability, its other magnetic properties are low coercivity, near zero magnetostriction, and significant anisotropic magnetoresistance. The low magnetostriction is critical for industrial applications, allowing it to be used in thin films where variable stresses would otherwise cause a ruinously large variation in magnetic properties. Permalloy's electrical resistivity can vary as much as 5% depending on the strength and the direction of an applied magnetic field. Permalloy typically have the face centered cubic crystal structure with a lattice constant of approximately 0.355 nm in the vicinity of a nickel concentration of 80%. A disadvantage of permalloy is that it is not very ductile or workable, so applications requiring elaborate shapes, such as magnetic shields, are made of other high permeability alloys such as mu metal. Permalloy is used in transformer laminations and magnetic recording heads.
Permalloy widely used in radio-electronic industry, precision instruments, remote control and automatic control system.
Normal composition%
| Ni | Fe | Mn | Si | Mo | Cu | C | P | S |
|---|---|---|---|---|---|---|---|---|
| 78.5~80.0 | Bal. | 0.6~1.1 | 0.3~0.5 | 3.8~4.1 | ≤0.2 | ≤0.03 | ≤0.02 | ≤0.02 |
Typical Mechanical properties
| Yield strength | Tensile Strength | Elongation |
|---|---|---|
| Mpa | Mpa | % |
| 980 | 1030 | 3~50 |
Typical Physical properties
| Property Name | Value |
|---|---|
| Density (g/cm3) | 8.6 |
| Electrical resistivity at 20ºC(Om*mm2/m) | 0.55 |
| Coefficient of linear expansion(20ºC~200ºC)X10-6/ºC | 10.3~11.5 |
| Saturation magnetostriction coefficient λθ/ 10-6 | 2.0 |
| Curie point Tc/ ºC | 450 |
High permeability soft magnetic alloy mainly nickel base alloy, nickel content is over 75%, this kind of alloy has the very high initial permeability and permeability.Often referred to as permalloy, also known as the early high magnetic conductivity alloy.They all have good processing performance, can be rolled into thin strip.Alloy is suitable for application in the ac weak magnetic field.Such as TV and instrumentation in various audio transformer, the high accuracy bridge transformer, transformer, magnetic shielding, magnetic amplifier, magnetic modulator, audio head, choke, precision electric meter of the piece and piece, etc.