Magnesium Wins on Specific Stiffness, Not Raw Strength

Magnesium alloys are not competing with steel or aluminium on absolute strength, covered on aluminium’s mechanics page for the same underlying comparison. They compete on the ratio that actually matters for a weight-limited component.

\frac{\sigma_y}{\rho}

Specific strength, the same metric used throughout this series. Magnesium's density (1.74 g/cm³) is low enough that even a moderate-strength magnesium alloy can match or beat a stronger but heavier aluminium or steel part on this ratio, the same logic that makes aluminium attractive against steel, one step further.

1.74 g/cm³

Magnesium density

2.70 g/cm³

Aluminium density

for comparison

7.87 g/cm³

Steel density

for comparison

Why die casting specifically suits magnesium

Because magnesium is comparatively difficult to form at room temperature, covered on this material’s materials science page, most structural magnesium use goes through die casting, injecting molten metal into a mould rather than bending or stamping a sheet. Magnesium die-casts with excellent fluidity and fills thin, complex mould geometry well, a real, specific processing advantage that happens to sidestep the one mechanical limitation the metal has.

Where magnesium actually gets used structurally

69%

Castings share of demand

15%

Aluminium-base alloys share

magnesium as an alloying addition

Sources: alloy properties and die-casting suitability draw on standard materials engineering references (International Magnesium Association, ASM Handbook); demand shares reference the demand data elsewhere on this site.