Nickel Base Magnetic Shielding Alloy - Mu Metal,Permalloy C, Mumetal, Mu-Metal,E FORU

### **Mu Metal (Permalloy C) - High Permeability Nickel-Iron Magnetic Shielding Alloy** #### **Overview** **Mu Metal** (commercially known as Mumetal, Mu-Metal, or Permalloy C) is a nickel-iron soft magnetic alloy renowned for having one of the highest magnetic permeabilities of any commercial alloy. Developed in the early 20th century, this specialized material exhibits extremely low coercivity and high magnetic saturation, making it exceptionally effective for shielding sensitive electronic components from static or low-frequency magnetic fields. The alloy's remarkable magnetic properties are achieved through a precise chemical composition followed by a critical final heat treatment in a pure hydrogen atmosphere, which removes impurities and creates large, strain-free grain structures essential for optimal magnetic performance. --- #### **Chemical Composition (Weight % - Typical)** | Element | Content (%) | | :--- | :--- | | **Nickel (Ni)** | **75.0 - 80.0** | | **Iron (Fe)** | **15.0 - 20.0** | | **Copper (Cu)** | **3.0 - 6.0** | | **Molybdenum (Mo)** | **2.0 - 4.0** | | **Chromium (Cr)** | **≤ 1.0** | | **Manganese (Mn)** | **0.50 - 1.50** | | **Silicon (Si)** | **0.30 - 0.70** | | **Carbon (C)** | **≤ 0.03** | | **Sulfur (S)** | **≤ 0.01** | *The high nickel content combined with copper and molybdenum creates the unique magnetic properties. The extremely low carbon and sulfur content is crucial for achieving high permeability.* --- #### **Physical & Magnetic Properties** | Property | Value / Description | | :--- | :--- | | **Density** | 8.70 - 8.80 g/cm³ | | **Melting Point** | ~1300-1350 °C (2370-2460 °F) | | **Curie Temperature** | **350-400 °C** (662-752 °F) | | **Electrical Resistivity** | 0.55-0.65 μΩ·m | | **Thermal Conductivity** | 20-25 W/m·K | | **Coefficient of Thermal Expansion** | 10-12 × 10⁻⁶/°C (20-100°C) | | **Initial Permeability (μi)** | **30,000 - 60,000** (0.002 T) | | **Maximum Permeability (μmax)** | **80,000 - 150,000** | | **Saturation Induction (Bsat)** | **0.70 - 0.82 T** (7000-8200 Gauss) | | **Coercivity (Hc)** | **< 0.5 - 2.0 A/m** (Extremely low) | | **Retentivity (Br)** | **0.2 - 0.4 T** | --- #### **Key Characteristics & Applications** **Key Characteristics:** 1. **Extremely High Magnetic Permeability**: Provides exceptional shielding effectiveness against low-frequency magnetic fields 2. **Very Low Coercive Force**: Requires minimal energy to magnetize and demagnetize 3. **Low Hysteresis Loss**: Minimal energy loss during AC magnetization cycles 4. **Sensitivity to Mechanical Stress**: Properties degrade significantly with cold working or mechanical shock, requiring careful handling 5. **Limited High-Temperature Use**: Magnetic properties deteriorate above ~400°C due to Curie temperature limitation **Typical Applications:** - **Magnetic Shielding**: CRT displays, electron microscopes, MRI rooms, photomultiplier tubes - **Aerospace & Defense**: Inertial navigation systems, satellite components, sensitive avionics - **Medical Equipment**: EEG, MEG systems, brain scanning equipment - **Research Instruments**: Mass spectrometers, particle accelerators, precision sensors - **Consumer Electronics**: High-end audio equipment, hard disk drives, smartphone sensors - **Power Electronics**: Current transformers, magnetic sensors, flux concentrators --- #### **International Standards & Trade Names** | Category | Designation | Description | | :--- | :--- | :--- | | **ASTM** | **A753 Type 4** | Standard specification for nickel-iron soft magnetic alloys | | **Military** | **MIL-N-14411C** | Military specification (Composition 1) | | **Trade Names** | **Mumetal®** | Original trade name (Telegraph Construction & Maintenance Co.) | | | **Permalloy C** | Western Electric designation | | | **HyMu 80** | Carpenter Technology designation | | **European** | **EN 10095 / Ni77Cr** | European norm for high permeability alloys | | **UNS** | **K94890** | Unified Numbering System classification | --- #### **Summary** **Mu Metal** represents the pinnacle of soft magnetic materials for low-frequency magnetic shielding applications. Its extraordinary permeability, approximately 100 times greater than that of ordinary steel, makes it indispensable for protecting sensitive electronic equipment from external magnetic interference. While the material is mechanically delicate and requires specialized annealing after fabrication, its unparalleled magnetic performance ensures its continued use in critical applications across medical, aerospace, research, and electronics industries. The alloy's effectiveness, combined with established international standards and multiple commercial sources, maintains its status as the benchmark material for challenging magnetic shielding requirements.

Packing of Standard Packing: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 3212 gallon liquid totes Special package is available on request.