Moly Permalloy Electrical Alloy,ASTM A-753; MIL-N-14411，1

### **Product Datasheet: Molybdenum Permalloy (Mo-Permalloy)** **A High-Performance Soft Magnetic Nickel-Iron Alloy** --- #### **1. Overview** **Molybdenum Permalloy**, commonly referred to as **Mo-Permalloy**, is a soft magnetic nickel-iron alloy with a significant addition of molybdenum. It is part of the "Permalloy" family, which is renowned for its high magnetic permeability, low coercivity, and high electrical resistivity. The primary advantage of the molybdenum addition is to significantly enhance the alloy's **electrical resistivity** and improve its **workability and ductility**, all while maintaining the exceptional soft magnetic properties of the binary nickel-iron system. This makes it ideal for AC applications where low core loss and high magnetic induction are critical. It is typically used in an annealed condition to develop its optimal magnetic properties. #### **2. Chemical Composition (Typical Weight %)** The composition is precisely controlled to achieve the desired magnetic and electrical characteristics. | Element | Content (%) | Role in the Alloy | | :--- | :--- | :--- | | **Nickel (Ni)** | Balance (~79 - 81) | Primary element for achieving high initial permeability and low magnetostriction. | | **Iron (Fe)** | ~15 - 17 | Balances the magnetic structure and saturation induction. | | **Molybdenum (Mo)** | ~4 - 5 | Key additive that increases electrical resistivity (reducing eddy current losses), improves ductility, and enhances magnetic stability. | | **Manganese (Mn)** | ~0.30 - 0.70 | Added as a deoxidizer and to control sulfur. | | **Silicon (Si)** | ≤ 0.30 | Residual element. | | **Carbon (C)** | ≤ 0.03 | Kept very low to prevent detrimental carbide formation that harms magnetic softness. | | **Sulfur (S)** | ≤ 0.02 | Residual element, kept low to prevent embrittlement. | #### **3. Physical & Magnetic Properties (Typical, Annealed Condition)** | Property | Value / Condition | | :--- | :--- | | **Density** | 8.74 g/cm³ | | **Curie Temperature** | ~460 °C (~860 °F) | | **Electrical Resistivity** | ~55 μΩ·cm | *[Significantly higher than pure iron or silicon steel]* | | **Saturation Induction (Bₛₐₜ)** | ~0.78 Tesla (7800 Gauss) | | **Initial Permeability (μᵢ)** | ~20,000 - 50,000 (depending on processing and annealing) | | **Maximum Permeability (μₘₐₓ)** | ~100,000 - 200,000 | | **Coercivity (H꜀)** | ~0.02 Oe | *[Very low, indicating soft magnetic character]* | | **Saturation Magnetostriction** | ~2 x 10⁻⁶ | *[Very low, leading to low magnetic noise]* | #### **4. Key Characteristics** * **High Permeability:** Allows for high magnetic flux with a low magnetizing force. * **Low Coercivity:** Requires very low energy to demagnetize, resulting in low hysteresis losses. * **High Electrical Resistivity:** Directly reduces eddy current losses, making it efficient for high-frequency AC applications. * **Low Magnetostriction:** Minimizes dimensional changes and acoustic noise under magnetic fields. #### **5. Heat Treatment** To develop its optimal soft magnetic properties, Moly Permalloy must undergo a final **high-temperature anneal in a pure, dry hydrogen atmosphere**. This process: * Relieves stresses from cold working. * Promotes grain growth. * Removes impurities (like carbon, sulfur, and oxygen) that pin magnetic domain walls. The cooling rate from the annealing temperature is critical and must be controlled to achieve the desired magnetic properties. #### **6. Product Applications** Mo-Permalloy is used in a wide array of sensitive electronic and electrical components, including: * **Magnetic Shields:** Enclosures to protect sensitive components from external magnetic fields. * **Transformers & Inductors:** Especially for low-level signal, pulse, and high-frequency applications. * **Toroidal Cores and Tape-Wound Cores:** For instruments and communication equipment. * **Saturable Core Reactors & Magnetic Amplifiers.** * **Recording Heads** in older tape and disk drive technologies. #### **7. International and Industry Standards** The alloy is covered by several key material specifications. * **ASTM:** * **ASTM A-753 - Type 4:** This is the primary standard, titled "Standard Specification for Wrought Nickel-Iron Soft Magnetic Alloys (UNS K94490)". Type 4 specifically covers the 79% Nickel - 4% Molybdenum - balance Iron alloy. * **Military Standard:** * **MIL-N-14411C (COMPOSITE):** This military specification covers "Nickel-Iron Alloy, Magnetic Core, Lamination and Tape, 79 Percent Nickel, 4 Percent Molybdenum". It details requirements for material supplied in strip form for magnetic cores. * **UNS:** K94490 * **Common Forms:** Cold-rolled strip, foil, sheet, and laminations. --- **Disclaimer:** The information provided herein is for reference purposes only. Magnetic and physical properties are highly dependent on the final heat treatment, cold work reduction, and exact composition. For design and procurement, the official, latest issue of the relevant material specification (ASTM A-753, MIL-N-14411) must be consulted. "Permalloy" is a historic trademark.

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 3373 gallon liquid totes Special package is available on request.