Magnesium HM31A O Wrought Alloy (UNS M13312)，Mg-3Th-1.2Mn， UNS M13312,E FOUR

### **Product Datasheet: Magnesium HM31A O (Annealed) Wrought Alloy (UNS M13312)** **Introduction** Magnesium HM31A-O (UNS M13312) is a high-temperature wrought magnesium alloy supplied in the annealed ("O") temper. The provided composition, Mg-3Th-1.2Mn, indicates a thorium-containing alloy, which aligns with the historical development of high-temperature magnesium alloys. **It is critical to note that the designation "HM31A" in modern standards typically refers to a rare-earth (e.g., Cerium, Neodymium) and zirconium-containing alloy, not a thorium-containing one.** The composition provided (Mg-3Th-1.2Mn) is characteristic of an earlier thorium-bearing alloy, which may be covered by older specifications. The "-O" temper indicates the material has been annealed, resulting in a soft, ductile state ideal for subsequent forming operations. **Key Features** * **Excellent Creep Resistance:** Designed to maintain strength at elevated temperatures, typically up to 345°C (650°F). * **High-Temperature Stability:** Suitable for applications requiring long-term exposure to heat. * **Good Formability in Annealed State:** The "O" temper provides maximum ductility for complex shaping and fabrication. * **Low Density:** Offers significant weight savings over aluminum and steel. ***Important Clarification:*** *This datasheet is based on the provided composition Mg-3Th-1.2Mn. Thorium-containing alloys are classified as low-level radioactive materials, subjecting them to specific handling, shipping, and disposal regulations. The modern, non-radioactive successor to these alloys is HM31A with a Rare Earth-Zirconium composition (UNS M13312), which has largely superseded the thorium-containing version for new applications.* --- #### **1. Chemical Composition (Weight %) - Based on Provided Data** The composition for this specific thorium-containing variant is as follows: | Element | Content (%) | | :---------------- | :---------------------------------- | | **Thorium (Th)** | 2.5 - 3.5 (Nominal 3.0) | | **Manganese (Mn)** | 1.0 - 1.5 (Nominal 1.2) | | **Magnesium (Mg)** | Remainder | | **Other Impurities** | ≤ 0.30 (total) | --- #### **2. Physical Properties** | Property | Value | | :---------------------------- | :-------------------------------------------- | | **Density** | ~1.80 g/cm³ (0.065 lb/in³) | | **Melting Point** | ~ 645°C (1195°F) | | **Thermal Conductivity** | 105 - 115 W/m·K | | **Coefficient of Thermal Expansion** | 25.0 - 26.0 µm/m·K at 20-200°C | | **Modulus of Elasticity** | 44 - 45 GPa (6.4 x 10⁶ psi) | --- #### **3. Mechanical Properties (Typical for O Temper)** The annealed ("O") temper offers lower strength but higher ductility, making it suitable for severe forming operations. Properties will be enhanced after subsequent aging treatments (e.g., to a T5 temper). **Room Temperature Properties (Annealed - O Condition):** | Property | Value | | :----------------------------- | :-------------------------------------------- | | **Tensile Strength, Ultimate** | 200 - 230 MPa (29,000 - 33,000 psi) | | **Tensile Strength, Yield (0.2% Offset)** | 130 - 160 MPa (19,000 - 23,000 psi) | | **Elongation** | 10% - 15% | **Elevated Temperature Properties (Aged Condition - indicative):** * **At 345°C (650°F):** Retains useful strength and excellent creep resistance. --- #### **4. International Standards** This specific thorium-containing alloy variant may be covered by historical or specific standards. The modern, rare-earth HM31A is covered by the standards below, which are often incorrectly associated with the thorium composition. * **ASTM:** * **ASTM B90 / B90M** - Standard Specification for Magnesium-Alloy Sheet and Plate (Covers HM31A, typically the RE-Zr type). * **AMS:** * **AMS 4392** - Sheet and Plate, Magnesium Alloy HM31A, As-Fabricated (Likely the modern composition). * *Older versions of AMS standards may have referenced the thorium-containing variant.* * **UNS:** **M13312** (This UNS designation is now associated with the rare-earth containing HM31A). * **SAE:** **J465** - Wrought Magnesium Alloys (Covers chemical requirements). --- #### **5. Product Applications** The primary application for this alloy, in its thorium-containing form, was in high-temperature aerospace components. The "O" temper was used for parts requiring significant forming before final heat treatment. * **Aerospace (Historical/Legacy):** * **Missile and Rocket Skin Panels:** Where aerodynamic heating is a factor. * **Engine Casings and Cowlings:** Non-critical structural components near jet engines. * **Aircraft Wing and Fuselage Skins:** For supersonic or high-performance aircraft. * **General Engineering:** * **Prototyping and Forming Trials:** The soft "O" temper is ideal for developing forming processes. **Fabrication & Heat Treatment Notes:** * **The O Temper Process:** The material is heated to a specific temperature and cooled slowly to relieve internal stresses and maximize ductility. * **Subsequent Heat Treatment:** Components fabricated from "O" temper material are often subsequently aged (T5 temper) to increase their strength. * **Welding:** Can be welded using Gas Tungsten Arc Welding (GTAW/TIG). Post-weld heat treatment is often required. * **Forming:** The "O" condition is the preferred state for complex or severe forming operations, which are typically performed hot. --- **Disclaimer:** This information is for reference purposes, specifically for the historical thorium-containing variant as per the provided composition. Properties can vary based on product form and processing. **Due to the thorium content, this specific alloy variant is subject to stringent regulatory controls.** For new designs, the modern, non-thorium HM31A (RE-Zr) or alloys like WE43 are strongly recommended. Always consult the latest and specific official material specifications for design, procurement, and manufacturing.

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 3341 gallon liquid totes Special package is available on request.