Magnesium AZ31B-O，UNS M11311;,E FOUR

Magnesium AZ31B-O (UNS M11311) Wrought Alloy Product Introduction** **Product Description:** Magnesium AZ31B-O is the annealed version of the common AZ31B wrought magnesium alloy. Designated under the Unified Numbering System as **UNS M11311**, the "-O" temper indicates that the material has been fully annealed. This heat treatment process involves heating the alloy to a specific temperature and cooling it slowly to relieve internal stresses from cold working or hot working, resulting in a soft, ductile, and dimensionally stable condition. This makes AZ31B-O ideal for subsequent severe forming operations where maximum ductility is required. --- #### **1. Chemical Composition (Weight %)** The chemical composition is identical to other tempers of AZ31B, conforming to strict international standards. | Element | Minimum (%) | Maximum (%) | Key Function | | :--- | :--- | :--- | :--- | | **Aluminum (Al)** | 2.5 | 3.5 | Primary strengthener, improves strength. | | **Zinc (Zn)** | 0.6 | 1.4 | Enhances strength and corrosion resistance. | | **Manganese (Mn)** | 0.2 | 1.0 | Crucial for improving corrosion resistance. | | **Silicon (Si)** | - | 0.10 | Impurity control. | | **Copper (Cu)** | - | 0.05 | Impurity control (minimized for corrosion resistance). | | **Iron (Fe)** | - | 0.005 | Impurity control (strictly limited). | | **Nickel (Ni)** | - | 0.005 | Impurity control (strictly limited). | | **Other Elements** | - | 0.30 (total) | - | | **Magnesium (Mg)** | **Balance** | | | *Note: The strict control of Fe, Cu, and Ni impurities is a hallmark of the "B" grade, ensuring superior corrosion resistance compared to the older AZ31A.* --- #### **2. Physical Properties** The physical properties are inherent to the alloy and are not significantly affected by the annealed temper. | Property | Value / Description | Condition | | :--- | :--- | :--- | | **Density** | 1.77 g/cm³ (0.064 lb/in³) | At 20°C | | **Melting Point** | ~ 605 - 630 °C (1121 - 1166 °F) | - | | **Thermal Conductivity** | 76 - 96 W/m·K | At 25°C | | **Coefficient of Thermal Expansion** | 26.0 μm/m·°C | 20 - 100°C | | **Electrical Resistivity** | ~ 92 nΩ·m | At 20°C | | **Modulus of Elasticity** | 45 GPa (6.5 x 10⁶ psi) | - | | **Shear Modulus** | 17 GPa (2.4 x 10⁶ psi) | - | | **Poisson's Ratio** | 0.35 | - | --- #### **3. Mechanical Properties (Typical for O Temper - Annealed)** The "-O" temper is characterized by lower strength and significantly higher ductility compared to the H24 or T1 tempers. | Property | Typical Value (Sheet, Annealed) | | :--- | :--- | | **Tensile Strength** | 225 - 240 MPa (33 - 35 ksi) | | **Yield Strength (0.2% Offset)** | 110 - 150 MPa (16 - 22 ksi) | | **Elongation** | 18 - 27% | | **Hardness** | 45 - 55 HB | *Note: The primary advantage of the O-temper is this high elongation, which allows for complex and deep forming operations.* --- #### **4. International Standards** AZ31B-O is specified in major international standards for wrought magnesium products. | Standard Organization | Standard Designation for AZ31B | | :--- | :--- | | **ASTM International** | **ASTM B90** (Sheet and Plate - includes O temper)
**ASTM B107/B107M** (Extruded Rod, Bar, Shapes) | | **SAE International** | **SAE J465** | | **UNS (Unified Numbering System)** | **M11311** | | **ISO (International Org. for Standardization)** | **ISO 3116** (Wrought Magnesium and Magnesium Alloys) | | **AMS (Aerospace Material Spec.)** | **AMS 4375** (Sheet and Plate - may specify annealed condition) | --- #### **5. Product Application & Forming** The AZ31B-O temper is primarily specified not for its final application strength, but for its superior formability. * **Primary Use: Severe Forming Operations** * **Deep Drawing:** Excellent for drawing complex, deep-shaped components. * **Stretch Forming:** Allows for significant deformation without cracking. * **Spinning:** Ideal for metal spinning processes to create axisymmetric parts. * **Any process requiring high ductility and low residual stress.** * **Final Applications (after forming, parts may be re-heat treated):** * **Aerospace:** Complexly shaped interior panels, housings, and ducts that are formed in the O-temper and may be used as-is or lightly hardened for final use. * **Automotive:** Intricately shaped inner door panels, seat shells, and structural brackets that undergo heavy deformation during manufacturing. * **Electronics:** Deep-drawn casings for specialized equipment. * **General Industry:** Complex-shaped covers, housings, and containers. --- #### **6. Key Characteristics & Considerations** * **Advantages of the O Temper:** * **Maximum Ductility:** Offers the highest formability of any AZ31B temper. * **Low Residual Stress:** The annealing process eliminates internal stresses from previous working, ensuring dimensional stability during and after machining or forming. * **Excellent Workability:** The soft condition is ideal for complex cold-forming operations. * **All Standard AZ31B Benefits:** Retains the alloy's lightweight, good machinability, and damping capacity. * **Considerations:** * **Lower Strength:** In its annealed state, it has the lowest strength of the AZ31B tempers. For final applications requiring high strength, the component is often formed in the O-temper and then heat-treated to a stronger temper (like T4 or T5). * **Corrosion:** The same considerations apply as for all magnesium alloys; protection is needed for harsh environments. * **Flammability:** Standard precautions for machining magnesium are required. **Summary:** **Magnesium AZ31B-O (UNS M11311)** is the soft, annealed condition of the widely used AZ31B alloy. Its primary value lies in its **exceptional ductility and formability**, making it the preferred choice for manufacturing processes that involve severe deformation. It serves as the optimal starting condition for forming complex components that may later be heat-treated to achieve higher strength for their final application.

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 3293 gallon liquid totes Special package is available on request.