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Magnesium Alloys

METALS
Magnesium has greater strength to weight than aluminium. However, it is more expensive, because the extraction process is energy intensive and costly. In the past it has been widely used in the production of bicycle components. Recently, bike frame manufacturers have begun to utilise its lightness, strength and durability in bespoke bike frame construction.

Properties
Magnesium is lightweight and strong. It is often alloyed with aluminium and zinc to improve its performance in specific forming applications and improve strength and resilience. Magnesium alloys are particularly susceptible to stress cracking, so sharp corners and notches should be designed out to avoid stress concentrations and potential stress cracking.
Magnesium is explosive in powdered form – it has a bright flame and is used for pyrotechnics and flares. The surface of magnesium tarnishes easily, and is corroded by saline and acidic solutions.

Processing
Magnesium alloys can be formed by metal spinning, superforming, casting, extrusion and are very easy to machine. Parts can be joined by certain arc welding processes (MIG and TIG), mechanical fixings (threads or rivets) and adhesive bonding. Typically, metal bike frames are constructed from tubular sections. Recent designs utilising cast, as opposed to extruded, magnesium sections have emerged that have the potential to redefine bike frame engineering.
The surface of magnesium alloys is generally coated to reduce corrosion. Suitable processes include powder coating, spray painting and metal plating.

Relevant Applications
Bike Frames
Magnesium alloys have very good mechanical dampening and high strength to weight. Dampening is the measure of a material's ability to absorb vibration. Magnesium alloys have been used in a small number of bespoke bicycle frames, but due to the high cost and reactive nature of the material, applications are limited.