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Permalloy 80 (1J79)
1. Product Overview
Permalloy 80 is a high-nickel Permalloy composed of about 79% nickel, 4% molybdenum, and balance iron; the Chinese equivalent grade is 1J79 (Ni79Mo4), a high-nickel Ni-Fe-Mo Permalloy, whose nominal composition is commonly written as Ni79Mo4, a Ni-Fe-Mo soft magnetic precision alloy, a high-nickel, high-permeability Permalloy for weak magnetic fields. After adequate hydrogen or vacuum annealing of the finished product, its initial relative permeability can reach 30000–60000, a maximum relative permeability of 200000–320000, and coercivity as low as 1.2–2.4 A/m, so that it responds markedly to very small applied fields.
The high-nickel matrix brings magnetocrystalline anisotropy and magnetostriction down to a low level, and together with molybdenum and strict impurity control it allows magnetic domains to rotate easily in very weak external fields, yielding very high initial and maximum permeability and very low coercivity. Typical trade names include Permalloy 80, HyMu 80, Mumetal and 4-79 Mo-Permalloy.
2. Chemical Composition
Permalloy 80 / 1J79 reference chemical composition (wt%)
Element | Reference range or max. | Role and control notes |
Ni | 78.5–80.0; 79.0–81.0 in some systems | Forms the basis of high-nickel Permalloy; governs magnetic anisotropy and cost |
Mo | 3.8–4.1; 4.8–5.2 in some Permalloy systems | Improves permeability, resistivity, and structural characteristics |
Mn | 0.60–1.10 | Assists metallurgy and property control |
Si | 0.30–0.50 | Alloying or residual element controlled per standard |
C | ≤0.03 | Even a slight excess significantly degrades magnetic properties |
P | ≤0.020 | Harmful impurity; affects processing and magnetic properties |
S | ≤0.020 | Harmful impurity; must be strictly controlled |
Cu | ≤0.20 | Residual element |
Fe | Balance | Matrix constituent element |
3. Grades, Standards, and Equivalents
Permalloy has many trade names, and different systems may specify different molybdenum contents, magnetic property units, and product form requirements, so "similar names" does not mean that all technical data are directly interchangeable.
Permalloy 80 (1J79) common grade and standard equivalents
Country or system | Grade / Name | Relevant standards | Notes |
China | 1J79 (Ni79Mo4) | GB/T 15018, GB/T 32286.1 | Precision alloy and magnetic material system; select according to product condition |
International trade names | Permalloy 80, HyMu 80, Mumetal | Manufacturer specifications or technical agreements | Widely used trademarks and common names; actual composition and properties may differ |
USA | 4-79 Mo-Permalloy, ASTM A753 Alloy 4 | ASTM A753 | Verify product form and performance grade |
Russia | 79HM | Relevant GOST system | Units, heat treatment, and test methods require written confirmation |
Japan | PC | Related material system | For grade identification only; substitution must be verified item by item |
France | Anny-sterM | Manufacturer or regional system | Trade names do not replace the material certificate |
4. Key Performance Parameters
Magnetic Properties
Permalloy 80 (1J79) typical magnetic properties in the fully annealed condition
Property | Symbol | Typical or reference range | Engineering notes |
Initial relative permeability | μi | 30000–60000 | Key metric for weak-field response; strongly affected by stress |
Maximum relative permeability | μm | 200000–320000 | Peaks within a specific field range |
Coercivity | Hc | ≤1.2–2.4 A/m | In the optimized ultra-thin strip condition, about 0.7–0.8 A/m |
Saturation magnetic induction (Bs) | Bs | 0.70–0.78 T | Noticeably lower than 1J50 and 1J22; saturates readily in strong fields |
Curie temperature | Tc | ≈450–455 °C | Does not represent the allowable long-term service temperature |
Electrical resistivity | ρ | 0.55–0.58 µΩ·m | AC performance also depends on strip thickness and lamination insulation |
Saturation magnetostriction coefficient | λs | ≈2×10⁻⁶ | Low magnetostriction helps reduce noise and stress-induced magnetic effects |
Permalloy 80 (1J79) permeability requirements expressed in mH/m and conversion between permeability and relative permeability values
Product form | Initial permeability | Maximum permeability | Conversion notes |
Cold-rolled strip | ≥25–31 mH/m | 125–250 mH/m | 1 mH/m ≈ 796 relative permeability |
Bar / wire / plate | ≥25 mH/m | ≥125 mH/m | Specific guaranteed values are determined by the product standard and performance grade |
By approximate conversion, 25 mH/m corresponds to a relative permeability of about 19900, 31 mH/m corresponds to about 24700, 125 mH/m corresponds to about 99500, 250 mH/m corresponds to about 199000. The two representations may differ in test conditions and definitions; at acceptance, use the units and methods of the standard specified in the contract, and do not judge conformity on numerical conversion alone.
Permalloy 80 (1J79) reference lower limits of AC elastic permeability for strip (peak field 0.1 A/m)
Strip thickness | Test frequency | Lower limit of AC elastic permeability | Selection notes |
0.02 mm | 1 kHz | ≥17.5 mH/m | Ultra-thin strip reduces eddy currents; suited to precision cores at higher frequencies |
0.02 mm | 10 kHz | ≥12.5 mH/m | Permeability decreases at higher frequency but remains at a relatively high level |
0.10 mm | 400 Hz | ≥22.5 mH/m | Suited to mutual inductors and precision transformers at low to medium frequencies |
0.10 mm | 1 kHz | ≥15 mH/m | Requires coordinated winding, annealing, and insulation control |
0.35 mm | 60 Hz | ≥25 mH/m | Maintains a relatively high response at power frequency |
0.35 mm | 400 Hz | ≥8.8 mH/m | With thicker strip, higher frequency significantly increases eddy current effects |
Physical and Mechanical Properties
Permalloy 80 (1J79) typical physical and service properties
Item | Typical value | Item | Typical value |
Density | 8.60 g/cm³ | Electrical resistivity | 0.55–0.58 µΩ·m |
Curie temperature | ≈450–455 °C | Saturation magnetostriction coefficient | ≈2×10⁻⁶ |
Long-term service temperature | Approx. −60–120 °C | Short-term temperature | ≤180 °C |
Material system | Ni-Fe-Mo | Nominal composition | Ni79Mo4 |
Permalloy 80 (1J79) typical room-temperature mechanical properties
Condition | Tensile strength | Yield strength | Elongation | Hardness |
Soft / annealed | 450–560 MPa | ≈150 MPa | ≥30%, up to 50% | HV 120–160; HBS approx. 120 |
Cold-worked (hard) condition | ≈1030 MPa | ≈980 MPa | ≈3% | HV 210–280 |
Permalloy 80 (1J79) has good ductility in the soft condition and is suitable for stamping, deep drawing, bending, and winding shielding cans or cores; however, cold working markedly raises strength and hardness and degrades magnetic properties. A material that"forms easily" is not necessarily ready for use after forming; critical magnetic parts still require final annealing in the finished or near-finished condition.
5. Available Forms and Specification Range
Permalloy 80 (1J79) common available forms and specification ranges
Form | Common specification range | Typical condition | Main applications |
Cold-rolled strip | Thickness 0.005–3.00 mm, width ≤300 mm | Cold-rolled, soft, or as agreed | Toroidal cores, laminations, shielding cans, and precision cores |
Ultra-thin strip | Down to 0.005 mm thick | Precision rolled, with controlled surface and flatness | Higher-frequency, small pulse, and high-sensitivity devices |
Hot-rolled flat bar | Thickness 4.5–20 mm | Hot-rolled or subsequent processing blank | Thicker magnetic circuit parts, machining blanks |
Hot-forged bar | Φ20–100 mm | As-forged, machining blank | Axisymmetric parts, pole pieces, and structural magnetic parts |
Wire and plate | Supplied as agreed | Drawn, rolled, soft, or semi-finished | Precision elastic magnetic parts, shielding, and machined components |
Toroidal cores | Customized by inner diameter, outer diameter, height, and strip thickness | Tape-wound, final annealed | Current transformers, chokes, pulse transformers |
Laminated / cut cores | Customized to drawing | Stamped, cut, stacked, final annealed | Relays, magnetic amplifiers, and special-shaped magnetic circuits |
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