How Much Weight Does Magnesium Actually Save vs Aluminium?
Not 35%. That's the density ratio (2.70 vs 1.74 g/cc), and it's the number every datasheet implies and no real part achieves.
Magnesium's elastic modulus is lower than aluminium's — 45 GPa against 71 GPa — so a stiffness-driven part needs deeper ribs or thicker walls to match the bending stiffness of the A380 part it replaces. That compensation hands back roughly a third of the theoretical saving. Magnesium claws some of it back by casting reliably at 1.0–1.5 mm walls, where A380 needs 2.0–2.5 mm.
The honest answer for a real die-cast housing or bracket: 20–30% mass out. The calculator below runs that compensation for your part in about thirty seconds — current mass, current material, and whether the design is stiffness- or strength-driven. No signup. And if the swap doesn't pay for your part, it will tell you to stay in aluminium.
Frequently asked questions
How much lighter is magnesium than aluminium? By density, magnesium is about 36% lighter than aluminium (1.74 vs 2.70 g/cc). On a real stiffness-driven casting, expect 20–30% after the walls are compensated for magnesium's lower modulus. Strength-driven parts land closer to the full density saving, because die-cast AZ91D's yield strength is comparable to A380's.
Is AZ91D as strong as A380/ADC12? In yield strength, effectively yes — both sit around 160 MPa as die-cast. The difference is stiffness (modulus), which is why honest magnesium conversions compensate wall and rib geometry rather than swapping the alloy one-for-one.
Doesn't magnesium corrode? Untreated magnesium in salt spray, yes. High-purity AZ91D with controlled Fe, Ni and Cu, protected by a conversion coat plus e-coat, passes automotive salt-spray requirements. The practical failure mode is galvanic — a steel fastener directly in a magnesium boss — and it's solved with isolation washers and coated inserts at the design stage.
Is magnesium a fire risk? Solid magnesium castings ignite far above their melting point; there is no product-level fire risk in a cast part. The hazard is fines and chips during machining, which is a shop-floor process control handled by any experienced magnesium machine shop.
Is magnesium more expensive than aluminium? Per kilogram, usually yes. Per part, the picture shifts: you buy fewer kilograms, die life is typically longer because magnesium is gentler on tooling, and cycle times run faster. Whether the total lands above or below your current part depends on volume and geometry — which is exactly what a DFMA review answers.
Who built this?
Exclusive Magnesium is a magnesium-only manufacturer — 30+ years across high-pressure die casting, gravity die casting, sand casting, CNC machining, forging and finishing, in AZ91D, AM50/60, AZ31B and WE43. We supply automotive, aerospace, defence, EV, drone and robotics OEMs in India, the EU and the US, with PPAP, FAI and CoC documentation as standard.