Overview

1J79 is a nickel-ferromagnetic alloy with a nickel content of about 80% and an iron content of about 20%. In 1914, Gustav Ehrmann, a physicist at Bell Telephone Laboratories, invented the alloy. Due to its high magnetic permeability, 1J79 is widely used as a magnetic core material for electrical and electronic devices, as well as a magnetic shielding material for shielding magnetic fields.

In commercial permalloy, its relative permeability is usually around 100,000, while the relative permeability of ordinary steel is only thousands. In addition to high permeability, 1J79 has other magnetic properties such as low coercivity, near zero magnetostriction, and significant anisotropic magnetoresistance. Low magnetostriction is very important for industrial applications because it allows 1J79 to be used in thin films that would otherwise result in large changes in magnetic properties under variable stress.

At 80% nickel concentration, Permalloy typically has a face-centered cubic crystal structure with a lattice constant of about 0.355 nm. However, one disadvantage of Permalloy is that it is not very malleable, so for applications requiring complex shapes, such as magnetic shielding, it is often made of other alloys with high magnetic conductivity, such as mu metal.

Nevertheless, 1J79 is still widely used in transformer pieces and magnetic recording heads. In addition, 1J79 is also widely used in the radio electronics industry, precision instruments, remote control and automatic control systems and other fields.

Limiting Chemical Composition, %

Nickel...................................................................................................................................................................................78.50-80.00

Molybdenum............................................................................................................................................................................3.80-4.10

Manganese..............................................................................................................................................................................0.60-1.10

Carbon......................................................................................................................................................................................0.03 max.

Copper......................................................................................................................................................................................0.20 max.

Iron........................................................................................................................................................................................13.03-16.60

Phosphorous............................................................................................................................................................................0.02 max.

Silicon.......................................................................................................................................................................................0.30-0.50

Sulfur.........................................................................................................................................................................................0.02 max.

Physical Constants

Tensile Properties

Heat treatment

Intermediate annealing: In order to eliminate all strain and return the alloy to a soft state suitable for further cold rolling or drawing, forming, bending or similar operations, annealing at 1020 to 1080 ° C for no more than 1 hour. Because high-nickel, high-permeability alloys readily absorb carbon, sulfur, oxygen, and other contaminants from combustion furnace gases, annealing should be carried out in dissociated ammonia, hydrogen, vacuum, or inert gas atmospheres during the process.

Final annealing: In order to obtain maximum softness and best magnetoelectric properties, the cold-deformed 1J79 alloy should be annealed at 1180 ° C for 3 to 5 hours in an oxygen-free dry hydrogen atmosphere with a dew point below -40 ° C, and then tempered.

Oil, grease, paint and all other contaminants must be removed before annealing. During hydrogen annealing, the individual parts should be separated by inert insulating powders such as magnesium and alumina.

Vacuum heat treatment can be used, but it usually results in a loss of magnetism compared to heat treatment in a dry hydrogen atmosphere.

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