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Understanding AZ91D Alloy Composition & Properties

    AZ91D Magnesium Alloy Composition


     Magnesium alloys have long been celebrated for their lightweight yet sturdy properties, and among them, AZ91D stands out as a versatile and widely used option. In this article, we delve into the composition, properties, applications, processing techniques, challenges, and future prospects of AZ91D magnesium alloy.

    AZ91D Magnesium Alloy Composition

    AZ91D comprises primarily magnesium (Mg), aluminum (Al), zinc (Zn), and traces of manganese (Mn) and other elements. This alloy boasts excellent mechanical strength, corrosion resistance, and thermal conductivity, making it a popular choice across industries.

    ElementContent (%)
    Aluminum, Al8.3-9.7
    Manganese, Mn0.15-0.50
    Zinc, Zn0.35-1
    Silicon, Si0.1
    Copper, Cu0.03
    Iron, Fe0.005
    Nickel, Ni0.002
    Others, each max0.02
    Magnesium, MgRemainder
    AZ91D Magnesium Alloy Composition

    Physical and Mechanical Properties

    Density1.8 g/cm³
    Melting Point536°C (997°F)
    Tensile Strength230 MPa (33,000 psi)
    Yield Strength140 MPa (20,000 psi)
    Elongation at Break3-5%
    Modulus of Elasticity45 GPa (6.5 x 10^6 psi)
    Poisson’s Ratio0.35
    Hardness (Brinell)60-70 HB
    Physical and Mechanical Properties of AZ91D Magnesium Alloy

    Thermal Properties

    Thermal expansion co-efficient (at 20-100°C/68-212°F)26 µm/m°C14.4 µin/in°F
    Thermal conductivity (at 20°C/68°F)72.7 W/mK504 BTU in/hr.ft².°F
    Magnesium Alloy AZ91D Thermal Properties

    Advantages and Disadvantages

    LightweightPoor elevated temperature strength
    High strength-to-weight ratioSusceptibility to stress corrosion cracking
    Good corrosion resistanceDifficulty in welding
    Excellent castabilityLimited availability of fabrication processes
    Good machinabilityLimited ductility and formability at room temperature
    High damping capacityHigher cost compared to some other alloys
    AZ91D Magnesium Alloy Advantages and Disadvantages


    The automotive industry utilizes AZ91D for lightweight components that enhance fuel efficiency and performance. In aerospace, it finds use in aircraft structures and components. Moreover, electronics and consumer goods benefit from its lightweight yet durable characteristics. Biomedical applications also leverage its biocompatibility and corrosion resistance. a

    Processing Techniques for AZ91D Magnesium Alloy

    1. Casting:
      • Sand Casting: Involves forming molds made of sand and then pouring molten AZ91D alloy into the mold cavity.
      • Die Casting: Utilizes reusable metal dies to produce complex-shaped components with high dimensional accuracy by injecting molten AZ91D alloy into the die cavity at high pressure.
      • Permanent Mold Casting: Uses reusable metal molds to produce near-net-shaped components with improved surface finish compared to sand casting.
    2. Extrusion:
      • Involves forcing heated AZ91D alloy through a shaped die to produce long, uniform cross-sections such as rods, bars, and tubes.
      • Enhances the mechanical properties of the alloy by aligning the grain structure and improving the strength and toughness of the extruded profiles.
    3. Forging:
      • Utilizes compressive forces to shape heated AZ91D alloy billets into desired forms.
      • Enhances the mechanical properties of the alloy by refining the grain structure and reducing porosity, resulting in components with higher strength and improved fatigue resistance.
    4. Machining:
      • Involves removing material from AZ91D alloy components using various cutting tools and techniques such as turning, milling, drilling, and grinding.
      • Requires special tooling and techniques due to the alloy’s low thermal conductivity and tendency to generate heat during cutting.
    5. Surface Treatments:
      • Anodizing: Forms a protective oxide layer on the surface of AZ91D alloy components to improve corrosion resistance and enhance surface hardness.
      • Plating: Deposits a layer of protective metal such as zinc, nickel, or chromium onto the surface of AZ91D alloy components to improve corrosion resistance and provide decorative finishes.
      • Painting/Coating: Applies protective coatings or paints to AZ91D alloy components to enhance corrosion resistance, improve aesthetics, and provide additional functional properties such as lubricity or thermal insulation.

    Each of these processing techniques offers unique advantages and considerations, allowing manufacturers to tailor the production process to meet specific design requirements and performance criteria for AZ91D magnesium alloy components.


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