AZ91 Magnesium Alloy

AZ91 is the most widely used benchmark grade among die-cast magnesium alloys. The "9" and "1" in its designation denote approximately 9% aluminium (Al) and 1% zinc (Zn) as the primary alloying elements respectively. Offering superb castability and well-balanced overall performance, it is currently one of the automotive industry's most extensively utilised magnesium alloys, accounting for roughly 90% of all magnesium die-cast components.

💡 Performance Characteristics: Engineered for Die-Casting

The core properties of AZ91 align seamlessly with the rigorous demands of automotive components:

• Exceptional lightweighting performance: With a density of only around 1.8 g/cm³, it delivers a 25% to 30% weight reduction compared to conventional aluminium alloys.

• Superb castability: Excellent fluidity makes it ideal for forming thin-walled and structurally intricate components.

• Moderate strength: Tensile strength is generally ≥230 MPa, which can be significantly elevated through secondary processes such as extrusion.

• Key limitation: Relatively poor corrosion resistance, typically requiring protective surface coatings.

🚗 Application Evolution: From "Structural Brackets" to "Core Assemblies"

Historically, AZ91 was predominantly used for non-critical areas such as steering wheel armatures and centre console brackets. With breakthroughs in advanced processing technologies like semi-solid injection moulding, its application has successfully expanded to core powertrain assemblies:

• NEV "Three-Electric" Powertrain Housings:

  • Electric drive housing: SAIC Motor pioneered the mass production of the world's first semi-solid moulded AZ91D magnesium alloy electric drive housing, weighing a mere 13.7 kg.

  • On-board charger housing: The AZ91D magnesium alloy charger casing utilised in Subaru PHEV models achieves a 25% weight saving over its aluminium counterpart.

  • Transmission housing: Compared to conventional die-cast aluminium units, semi-solid AZ91D magnesium alloy housings achieve approximately 30% weight reduction.

• Engine peripheral components:

  • Flywheel housing: FAW Casting & Forging has developed a commercial-vehicle AZ91D magnesium alloy flywheel housing weighing just 16 kg, cutting weight by 30%.

The definitive advantage of AZ91 magnesium alloy lies in its balance between weight reduction and castability. Although its corrosion resistance remains a challenge, modern advancements in cutting-edge techniques like semi-solid moulding are breaking through these barriers—driving its transition from minor interior structural parts to critical powertrain assemblies such as electric drive units and gearbox casings.