Magnesium — Ultralight Structural Metal

Magnesium was first isolated by Sir Humphry Davy in 1808, but commercial production did not begin until the early 20th century. Germany was the first major producer, using magnesium extensively in military aircraft during both World Wars. The Volkswagen Beetle used magnesium alloy for its engine block and transmission housing. Modern production is dominated by China, which accounts for about 85% of global output.

Magnesium has a density of 1.74 g/cm3, melting point of 650 degC, and HCP crystal structure that limits room-temperature ductility. Common alloys like AZ91 (die-cast) reach 230 MPa tensile strength, while wrought alloys like AZ31 are used for sheet and extrusion. Magnesium has excellent vibration damping capacity — about 10 times greater than aluminum — and good electromagnetic shielding properties.

Automotive applications include steering wheels, instrument panels, seat frames, and transmission housings (BMW, Ford, GM). Consumer electronics use magnesium for laptop and camera casings (e.g., Apple MacBook internal frame). Aerospace uses include helicopter gearbox housings and missile components. Magnesium is also a critical alloying element in aluminum alloys (5xxx and 7xxx series) and is used as a desulfurizing agent in steel production.

Lowest density of any structural metal enables significant weight savings. Excellent specific stiffness (elastic modulus per unit density). Superior vibration damping for noise-sensitive applications. Good electromagnetic shielding for electronics. High-pressure die castability with thin wall sections and complex geometries.

Flammable in finely divided form — requires Class D fire extinguishers and careful machining practices (dry machining or special coolants). Limited room-temperature ductility due to HCP crystal structure. Susceptible to galvanic corrosion when in contact with most other metals. Creep resistance is poor above 120 degC for common alloys, though rare-earth-containing grades (WE43, Elektron 21) improve high-temperature performance.

Magnesium is recyclable, requiring about 5% of the energy for primary production. However, recycling requires protective atmospheres (SF6 or newer alternatives) to prevent oxidation during remelting. Clean, segregated scrap achieves high recovery rates, but mixed or contaminated scrap is more challenging. The industry is transitioning away from SF6 cover gas due to its extreme global warming potential.