Magnesium HK31A-T6，UNS M13310;,E FOUR

### **Technical Datasheet: Magnesium Alloy HK31A-T6, UNS M13310** --- #### **1. Material Overview** HK31A-T6 is a high-temperature magnesium-thorium alloy supplied in the solution heat-treated and artificially aged condition. This alloy was developed for applications requiring exceptional elevated temperature performance, offering excellent creep resistance and mechanical properties retention at temperatures up to 350°C. While thorium-containing alloys have seen reduced usage due to radioactivity concerns, HK31A remains important for certain high-temperature applications. --- #### **2. Key Features** - **Exceptional high-temperature strength** up to 350°C - **Outstanding creep resistance** - **Good castability** for complex components - **Excellent thermal stability** - **Good corrosion resistance** - **Superior strength retention** at elevated temperatures --- #### **3. Chemical Composition (Weight %)** | Element | Composition (%) | |---------|-----------------| | **Thorium (Th)** | 2.5–4.0% | | **Zirconium (Zr)** | 0.4–1.0% | | **Zinc (Zn)** | ≤ 0.30% | | **Manganese (Mn)** | ≤ 0.20% | | **Silicon (Si)** | ≤ 0.05% | | **Copper (Cu)** | ≤ 0.10% | | **Iron (Fe)** | ≤ 0.05% | | **Nickel (Ni)** | ≤ 0.01% | | **Other Elements** | ≤ 0.30% | | **Magnesium (Mg)** | Balance | *Note: Thorium content provides the exceptional high-temperature properties through precipitation strengthening mechanisms. Special handling requirements apply due to low-level radioactivity.* --- #### **4. Mechanical Properties (T6 Temper)** | Property | Room Temperature | 300°C (572°F) | 350°C (662°F) | |----------|------------------|---------------|---------------| | **Ultimate Tensile Strength** | 230–260 MPa | 120–140 MPa | 90–110 MPa | | **Tensile Yield Strength (0.2%)** | 170–200 MPa | 90–110 MPa | 70–90 MPa | | **Elongation (% in 50mm)** | 4–8% | 8–15% | 10–20% | | **Compressive Yield Strength** | 170–200 MPa | 90–110 MPa | 70–90 MPa | | **Hardness (Brinell)** | 70–80 HB | 45–55 HB | 35–45 HB | | **Shear Strength** | 140–160 MPa | 80–100 MPa | 60–80 MPa | | **Fatigue Strength** | 100–120 MPa | 60–80 MPa | 40–60 MPa | --- #### **5. Physical Properties** | Property | Value | |----------|-------| | **Density** | 1.78 g/cm³ | | **Melting Range** | 565–650°C | | **Specific Heat** | 1.04 kJ/kg·K | | **Thermal Conductivity** | 118 W/m·K | | **Coefficient of Thermal Expansion** | 27.0 μm/m·K | | **Modulus of Elasticity** | 44 GPa | --- #### **6. Heat Treatment Cycle (T6)** - **Solution Treatment:** 565°C ± 5°C for 4–8 hours - **Quenching:** Hot water (70–100°C) - **Artificial Aging:** 200°C ± 5°C for 16–24 hours - **Cooling:** Air cool - **Microstructure:** Fine-grained with thorium-containing precipitates --- #### **7. Applicable Standards** - **ASTM International:** - **ASTM B80** – Standard Specification for Magnesium-Alloy Sand Castings - **ASTM B199** – Standard Specification for Magnesium-Alloy Permanent Mold Castings - **Aerospace Standards:** - **AMS 4380** – Magnesium Alloy Castings, Sand 3Th-0.7Zr (HK31A-T6) - **SAE International:** - **SAE J465** – Magnesium Alloy Castings - **Unified Numbering System:** - **UNS M13310** - **Military Standards:** - **MIL-M-46062** – Magnesium Alloy Castings, High Strength --- #### **8. Manufacturing Characteristics** - **Casting Methods:** Sand casting, permanent mold casting - **Pouring Temperature:** 750–810°C - **Fluidity:** Good - **Hot Tearing Resistance:** Good - **Machinability:** Good (standard magnesium machining practices) - **Weldability:** Good (TIG welding with proper filler) --- #### **9. Applications** - **Aerospace Components:** - Jet engine compressor casings - Missile components - Rocket motor cases - Aircraft firewalls - High-temperature structural components - **Nuclear Applications:** - Nuclear reactor components (historical applications) - Radiation shielding components - **Industrial Equipment:** - High-temperature pump components - Compressor parts - Specialized high-temperature machinery --- #### **10. Special Handling Requirements** - **Radiation Safety:** Low-level radioactive material requiring proper handling - **Disposal:** Special disposal procedures required - **Documentation:** Complete traceability and documentation mandatory - **Regulatory Compliance:** Subject to nuclear regulatory controls --- #### **11. Corrosion Performance & Protection** - **Atmospheric Corrosion:** Good resistance - **High-Temperature Oxidation:** Excellent up to 400°C - **Recommended Coatings:** High-temperature conversion coatings, specialized paints - **Galvanic Corrosion:** Standard isolation practices required --- #### **12. Design Guidelines** - **Maximum Service Temperature:** 350°C continuous, 400°C short-term - **Section Thickness:** 4–60 mm recommended - **Thermal Considerations:** Excellent for thermal cycling applications - **Regulatory Compliance:** Ensure compliance with radiation safety regulations --- #### **13. Comparison with Similar Alloys** - **vs. HZ32A-T5:** Better high-temperature strength - **vs. WE43-T6:** Higher maximum service temperature - **vs. Conventional Mg Alloys:** Significantly superior high-temperature performance --- **Note:** HK31A-T6 represents a specialized class of high-temperature magnesium alloys with exceptional thermal stability. While thorium-containing alloys offer outstanding high-temperature properties, their usage is increasingly restricted due to radioactivity concerns. For new designs, consider non-radioactive alternatives like WE43 or WE54 alloys. For existing applications, strict adherence to radiation safety protocols is essential. Always consult with materials engineering and radiation safety specialists when working with this alloy.

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 3333 gallon liquid totes Special package is available on request.