1J79 Alloy

1J79 (also known as Supermalloy in international standards) is a premium iron-nickel (Fe-Ni) based high-permeability soft magnetic alloy, belonging to the Permalloy family, specifically engineered for high-precision low-frequency magnetic applications requiring ultra-high initial magnetic permeability, extremely low coercivity, and excellent magnetic stability. Unlike 1J50 (a standard Permalloy with balanced soft magnetic properties), 1J79 achieves superior magnetic performance through optimized nickel content (≈80%), strict impurity control (especially C, S, P), and specialized annealing processes — the high nickel content forms a more homogeneous austenitic structure, minimizing magnetic domain pinning sites and enabling ultra-smooth domain movement. This alloy excels in ultra-low-frequency (5-400Hz) and weak magnetic field environments, making it the material of choice for high-precision magnetic sensors, magnetic shielding for sensitive electronics, and low-noise magnetic components.

Notably, 1J79 maintains exceptional magnetic stability over a wide temperature range (-60℃ to 120℃) and exhibits extremely low magnetic hysteresis loss, ensuring ultra-high signal-to-noise ratio (SNR) in magnetic circuits. Its excellent cold workability allows for manufacturing of ultra-thin strips (down to 0.005mm) and micro-sized components, while its good corrosion resistance (superior to 1J50) extends service life in humid or mild corrosive environments. It is widely used in aerospace precision instruments, medical imaging equipment, quantum technology, and high-end consumer electronics where ultra-high magnetic performance and reliability are critical. The following is a comprehensive breakdown of its chemical composition, physical properties, magnetic properties, and application products.

1. Chemical Composition (Mass Fraction, %)

2. Key Magnetic Properties (After Standard Heat Treatment: 1100-1150℃ vacuum annealing for 4-6h, furnace cooling to 500℃ at ≤20℃/h, then air cooling)

Magnetic properties are the defining characteristics of 1J79, with performance metrics significantly superior to standard soft magnetic alloys like 1J50:

Key Notes on Magnetic Properties:

• Ultra-high Initial Permeability (μᵢ ≥80,000μ₀): 3-4 times higher than 1J50, enabling the alloy to detect extremely weak magnetic fields (down to 10⁻⁸T) — critical for quantum sensors and medical imaging equipment;
• Extremely Low Coercivity (Hc ≤1.5A/m): 3-5 times lower than 1J50, minimizing magnetic hysteresis loss and ensuring ultra-low noise in magnetic circuits (e.g., low-noise amplifiers);
• Moderate Saturation 磁感应强度 (Bs ≥0.70T): Lower than 1J50, but sufficient for low-power, high-precision applications (e.g., sensor cores), where permeability and noise performance take priority over flux density;
• Excellent Permeability Stability (Δμᵢ/μᵢ ≤8%): Maintains consistent performance under thermal stress and long-term use, ensuring reliability in aerospace and medical devices with strict lifespan requirements;
• Low Curie Temperature (Tc ≥390℃): Limits high-temperature applications (practical use ≤120℃), but sufficient for most precision electronic and instrument scenarios.
• Density: Approximately 8.70g/cm³ at room temperature (25℃), higher than 1J50 (8.20g/cm³) due to higher nickel and molybdenum content, but lower than high-alloyed soft magnetic materials (e.g., Fe-Co-V alloys: 8.90g/cm³). This density is acceptable for precision components (e.g., micro-sensor cores) where performance outweighs weight concerns.
• Melting Temperature Range: 1420-1470℃ (liquidus: ~1470℃; solidus: ~1420℃). The narrow melting range, combined with vacuum melting, ensures minimal composition segregation — critical for uniform magnetic properties across large batches of ultra-thin strips.
• Thermal Expansion Coefficient (CTE):

3. Physical Properties

3.1 Basic Physical Parameters

◦ 20-100℃: ~11.8×10⁻⁶/℃

◦ 20-300℃: ~12.8×10⁻⁶/℃

◦ 20-400℃: ~13.5×10⁻⁶/℃

The lower and more gradual CTE compared to 1J50 minimizes thermal stress during temperature fluctuations (e.g., in aerospace electronics), reducing magnetic property drift and component deformation.

• Thermal Conductivity (λ):

◦ 100℃: ~16.5W/(m·K)

◦ 300℃: ~19.0W/(m·K)

◦ 400℃: ~21.0W/(m·K)

Lower thermal conductivity than 1J50 reduces heat transfer between magnetic components and sensitive electronics (e.g., quantum chips), preventing thermal interference with ultra-precision measurements.

3.2 Mechanical Properties (After Cold Rolling + Vacuum Stress-Relief Annealing)

Key Notes:

• Exceptional Cold Workability: The combination of high elongation (δ₅ ≥30%) and reduction of area (ψ ≥65%) allows rolling into ultra-thin strips (0.005-0.1mm) and drawing into fine wires (0.01-0.5mm) — essential for miniaturized components in microelectronics and MEMS (Micro-Electro-Mechanical Systems);
• Low Hardness (HV 110-140): Easier to punch, bend, and cut than 1J50, enabling the production of complex microstructures (e.g., multi-layer magnetic shielding for chip-scale devices);
• Stress Sensitivity: Mechanical stress (e.g., from bending or assembly) can reduce permeability by 10-15% — vacuum stress-relief annealing after processing is mandatory to restore optimal magnetic performance.

4. Application Products & Industry Scenarios

4.1 Precision Instrumentation & Quantum Technology Field

As the gold standard for ultra-high-precision magnetic components, 1J79 is used for:

• Quantum Sensors: Cores of SQUID (Superconducting Quantum Interference Device) magnetometers and atomic magnetometers, leveraging ultra-high initial permeability (μᵢ ≥80,000μ₀) to detect magnetic fields as weak as 10⁻¹⁵T — critical for brain imaging (MEG), geological exploration, and dark matter research;
• Precision Current Transformers: Cores of micro-current transformers (for measuring currents ≤1mA) in electrical metering and semiconductor manufacturing, where extremely low coercivity (Hc ≤1.5A/m) ensures measurement accuracy (error ≤±0.01%);
• Optical Isolators: Magnetic cores in fiber optic isolators and circulators, maintaining stable magnetic flux density (Bs 0.75-0.85T) to prevent signal interference in high-speed optical communication networks (100Gbps+).

4.2 Aerospace & Defense Field

In aerospace and defense systems requiring ultra-low-noise and stable magnetic performance, 1J79 is applied to:

• Aerospace Magnetic Shielding: Multi-layer shielding enclosures for satellite-borne quantum sensors, inertial navigation systems (INS), and atomic clocks, blocking external magnetic interference (≤1nT) and ensuring positioning accuracy (≤0.1m/h);
• Missile Guidance Components: Cores of magnetic torque rods and attitude control sensors in missile guidance systems, where permeability stability (Δμᵢ/μᵢ ≤8%) ensures trajectory accuracy under extreme temperature fluctuations (-60℃ to 80℃);
• Secure Communication Equipment: Low-noise transformer cores in encrypted communication systems, minimizing magnetic interference-induced signal distortion (bit error rate ≤10⁻⁹).

4.3 Medical & Biomedical Field

In medical devices requiring ultra-high magnetic sensitivity and biocompatibility, 1J79 is used for:

• Medical Imaging Accessories: Magnetic shielding for MRI (Magnetic Resonance Imaging) gradient coils and patient monitoring sensors, reducing external magnetic noise and improving image resolution (down to 0.1mm);
• Biomedical Sensors: Cores of magnetocardiography (MCG) and magnetoencephalography (MEG) sensors, detecting weak magnetic fields from the heart (≤10⁻¹⁰T) and brain (≤10⁻¹²T) without invasive procedures;
• Drug Delivery Systems: Magnetic cores in targeted drug delivery microdevices, enabling precise control of drug release via external weak magnetic fields (H ≤0.1A/m).

4.4 High-End Electronics & Consumer Tech Field

In high-end electronics demanding low-noise and miniaturization, 1J79 is used for:

• Chip-Scale Magnetic Shielding: Ultra-thin (0.005-0.01mm) shielding films for 5G RF chips, AI processors, and quantum computing chips, blocking on-chip magnetic crosstalk (isolation ≥60dB at 100Hz);
• High-End Audio Equipment: Cores of ultra-low-noise audio transformers in high-fidelity (Hi-Fi) amplifiers and headphones, minimizing hysteresis loss (P₀.₈/50 ≤0.35W/kg) and achieving signal-to-noise ratio (SNR) ≥120dB;
• Wireless Charging for Precision Devices: Cores of wireless charging coils in medical wearables (e.g., glucose monitors) and smartwatches, ensuring efficient energy transfer (efficiency ≥90%) with minimal magnetic interference to sensitive sensors.
• Smelting: Vacuum induction melting (VIM) with secondary vacuum refining is mandatory to control impurity content (C ≤0.02%, S ≤0.015%) — air melting is prohibited, as it introduces oxide and sulfide inclusions that destroy magnetic performance;
• Cold Working:

5. Processing & Heat Treatment Recommendations

◦ Ultra-thin Strips (≤0.01mm): Multi-pass rolling with intermediate vacuum annealing (900-950℃, 2h) after every 10-15% deformation to avoid cracking; rolling speed must be controlled (≤1m/s) to prevent work hardening-induced magnetic degradation;

◦ Strips/Wires (>0.01mm): Single-pass rolling/drawing with 20-30% deformation, followed by final stress-relief annealing;

• Heat Treatment:

◦ Magnetic Property Optimization Annealing: 1100-1150℃ vacuum annealing (vacuum degree ≤10⁻⁴Pa) for 4-6h, furnace cooling to 500℃ at ≤20℃/h (slow cooling critical for homogeneous grain growth), then air cooling — this process maximizes permeability and minimizes coercivity;

◦ Post-Processing Stress-Relief Annealing: 850-900℃ vacuum annealing for 1-2h, air cooling — required after any bending, stamping, or assembly to eliminate residual stress (restores 95% of optimal magnetic performance);

• Machining & Assembly:

◦ Machining must be done with sharp, low-friction tools (e.g., diamond tools) to minimize surface stress; dry machining is preferred to avoid contamination;

◦ Assembly should use non-magnetic fasteners (e.g., titanium, plastic) to prevent magnetic shunting; components must be handled with clean gloves to avoid oil/grease contamination (which degrades annealing effectiveness).

This comprehensive performance and application profile establishes 1J79 as the premier soft magnetic alloy for ultra-high-precision, low-frequency magnetic applications. Its unique combination of ultra-high permeability, extremely low coercivity, and excellent stability makes it irreplaceable in fields where magnetic performance directly determines the accuracy, sensitivity, and reliability of critical systems.