Magnesium die casting is a high-pressure manufacturing process used to produce complex, thin-walled, lightweight metal components with excellent dimensional accuracy and surface finish.
As magnesium is the lightest structural metal, die casting is the most economical and technically efficient method for high-volume production in automotive, electronics, aerospace, power tools, and consumer products.
Why Magnesium Is Ideal for Die Casting
✔ Density: 1.74 g/cm³ (≈33% lighter than aluminum)
✔ Very low molten viscosity – fills thin sections easily
✔ Lower latent heat of fusion – rapid solidification
✔ Excellent fluidity – complex geometries achievable
✔ Reduced die erosion – longer tool life
Common Magnesium Die Casting Alloys
| Alloy | Composition (Approx.) | Key Features | Typical Uses |
|---|---|---|---|
| AZ91D | 9% Al, 1% Zn | Best overall balance | Auto housings, electronics |
| AM60B | 6% Al, Mn | High ductility & impact | Steering wheels |
| AM50A | 5% Al, Mn | Superior crash energy | Safety components |
| AS41 | Al + Si | Improved creep resistance | Powertrain parts |
| AE42 | Al + rare earths | High-temperature stability | Transmission housings |
Magnesium Die Casting Processes
Hot-Chamber Die Casting (Most Common)
Molten magnesium is contained in a sealed crucible under protective gas.
The injection system is immersed in the melt, enabling fast cycles and
excellent surface quality.
Advantages:
✔ Faster cycle times
✔ Reduced oxidation
✔ Superior surface finish
Cold-Chamber Die Casting (Limited Use)
Used for specialty or large parts where molten metal is ladled into the shot
chamber. Oxidation risk is higher.
Typical Mechanical Properties (AZ91D)
| Property | Typical Value |
|---|---|
| Tensile Strength | 220 – 250 MPa |
| Yield Strength | 140 – 160 MPa |
| Elongation | 2 – 4% |
| Hardness | ~80 HB |
| Fatigue Strength | Moderate |
| Elastic Modulus | ~45 GPa |
Physical Properties of Magnesium
| Property | Value |
|---|---|
| Density | 1.74 g/cm³ |
| Melting Point | ~650 °C |
| Thermal Conductivity | 90 – 160 W/m·K |
| Electrical Conductivity | ~38% IACS |
| Damping Capacity | Excellent |
| EMI Shielding | Very good |
Solidification & Metallurgical Behavior
Crystal Structure: HCP (α-Mg matrix)
Microstructure:
α-Mg grains with β-Mg₁₇Al₁₂ intermetallic phase (AZ alloys)
Strengthening Mechanisms:
✔ Solid solution strengthening (Al, Zn)
✔ Intermetallic strengthening
✔ Grain refinement due to rapid solidification
Key Insight:
Rapid cooling produces fine microstructures, increasing strength while
reducing ductility.
Design Guidelines
Wall thickness: 1.0 – 3.0 mm (thinner than aluminum)
Draft angle: 0.5° – 1.0° per side
Rib thickness: ≤ 60% of wall thickness
Tolerances: ±0.05 – 0.1 mm achievable
Surface Finish & Secondary Operations
As-cast finish is smooth and fine-grained, ideal for coatings.
Secondary operations include CNC machining, tapping, shot blasting, anodizing, powder coating, and chromate-free conversion coatings.
Corrosion Protection
Magnesium requires surface protection in most environments:
Chemical conversion coatings
Anodizing
E-coating
Powder coating
Multi-layer paint systems
Applications
Automotive
Steering wheels, transmission housings, seat frames, brackets
Electronics
Laptop & mobile housings, camera bodies, EMI enclosures
Aerospace
Interior components, structural housings
Industrial & Consumer
Power tools, medical equipment housings, sports equipment
Advantages
✔ 30–75% lighter than steel
✔ 33% lighter than aluminum
✔ Excellent dimensional accuracy
✔ High production rates
✔ Reduced machining
✔ Long die life
✔ Outstanding stiffness-to-weight ratio
Limitations
❌ Lower ductility than wrought magnesium
❌ Requires corrosion protection
❌ Higher material cost than aluminum (offset by weight savings)
Why Choose Magnesium Die Casting?
Choose magnesium die casting when maximum weight reduction, thin-wall designs, complex geometry, EMI shielding, and high-volume production are critical to lifecycle cost and performance.