I. Physical Properties and Mechanical Performance
Density and Lightweighting
Magnesium alloy has a density of only 1.74g/cm³ (e.g., AZ31 grade), about 35% lighter than aluminum alloy (2.7g/cm³).
With equivalent strength, magnesium alloy enables more extreme lightweighting. For instance, a bicycle frame made with magnesium alloy can reduce weight by 30%, cutting energy consumption by 5% over 100 km of cycling.
Strength and Hardness
| Property | Magnesium Alloy (AZ31) | Aluminum Alloy (6061-T6) | Alumold500 Aluminum Alloy |
|---|---|---|---|
| Tensile Strength | 220 MPa | 276 MPa | 472 MPa |
| Specific Strength | 126 MPa/(g/cm³) | 102 MPa/(g/cm³) | 170 MPa/(g/cm³) |
| Typical Hardness | 40–100 HRB | 60–100 HRB | 80–85 HRB |
Durability and Service Life
Magnesium alloys have significantly lower fatigue life than aluminum alloys. For example, magnesium bicycle frames typically last 2–3 years (frequent replacement needed), while aluminum frames can serve for over 5 years.
Aluminum molds (like Alumold500) can last up to 150,000 cycles, while magnesium molds require more frequent maintenance due to lower thermal stability.
II. Processing and Cost Differences
Die Casting Process Comparison
| Parameter | Magnesium Alloy | Aluminum Alloy |
|---|---|---|
| Melting Temperature | 620–680°C (inert gas) | 610–670°C (nitrogen) |
| Injection Speed | 100 m/s (wall 0.5 mm) | 30–60 m/s (wall ≥1.2 mm) |
| Mold Lifespan | 100k–150k cycles | 50k–80k cycles |
Cost Composition
Magnesium alloy production requires inert gas protection (SF₆ + CO₂), leading to equipment costs 40% higher than aluminum.
Total cost for magnesium rods: approx. ¥120/kg
Aluminum rods: ¥30–50/kg,
However, weight-saving benefits of magnesium can offset part of the cost.
III. Application Suitability
When to Prefer Magnesium Alloy
Aerospace: Ultra-light structural parts (e.g., cabin interiors), where reduced weight directly improves fuel efficiency
Sports Equipment: Competition-grade bicycles and e-bikes – reducing 1 kg can boost acceleration by 8%
Mobile Buildings: Superior seismic performance compared to aluminum, reducing vibration transfer by 30%
Aluminum Alloy Advantage Scenarios
Mold Manufacturing: Alumold500 offers 472 MPa tensile strength and low thermal expansion – ideal for precision injection molds
Electrical Equipment: High conductivity ≥61% IACS (e.g., 1350-O aluminum rods), suitable for high-current needs
Corrosion-Resistant Structures: E.g., solar panel frames – salt spray resistance >3000 hours, with lower life-cycle costs
IV. Limitations and Risks
Magnesium Alloy Limitations
Oxidation Risk: Magnesium self-ignites at 310°C; strict anti-explosion measures are required during processing. Oxidation rate is 3× faster than aluminum.
Heat Dissipation: Thermal conductivity is only 156 W/(m·K) vs. aluminum's 205 W/(m·K), limiting high-temperature performance.
Aluminum Alloy Limitations
Lower specific strength compared to magnesium; extreme lightweighting may require carbon fiber alternatives
High-strength aluminum (e.g., 7075-T6) has lower toughness and needs additional surface treatment to prevent stress corrosion
Selection Recommendation
If extreme lightweighting is the priority and budget allows, choose magnesium alloys (e.g., AZ31 rods), with anti-oxidation coatings
For durability and cost-effectiveness in construction or power applications, use high-performance aluminum alloys (e.g., 6061-T6 or Alumold500)
