Alloy
AZ80 in detail.
AZ80 is a magnesium wrought alloy with around eight percent aluminium, up to one percent zinc and a manganese addition. The aluminium content enables precipitation hardening; the alloy remains formable at forging temperature.
The Formula 1 technical regulations prescribe magnesium grades AZ70 or AZ80 for wheels. In the mbDESIGN program, AZ80 works in road-approved wheels.
Forming
Forging versus casting.
Casting leaves microporosity in the material – preferred starting points for fatigue cracks. Forging closes pores under high pressure and aligns the grain with the component geometry.
For AZ80 the effect is measurable: tensile strength rises from roughly 168 MPa as-cast to 345–380 MPa in the forged state. Elongation increases from two to three percent to six to thirteen percent; fatigue strength rises by a double-digit percentage.
Design
Stiffness decides the geometry.
Magnesium is a third lighter than aluminium, but its elastic modulus is lower as well – 44 versus 69 GPa. The specific stiffness of both materials is nearly identical.
A magnesium wheel therefore does not copy an aluminium design. Stiffness-critical sections are sized up deliberately. The result on the finished wheel: 20 to 30 percent less weight, with stiffness and strength targets met.
Testing
Tested like any road wheel.
Road approval does not distinguish between materials. The forged mbDESIGN magnesium wheel passed the test procedures required for road wheels – including rotating bending, rolling and impact testing – and was approved by the German Federal Motor Transport Authority (KBA) in 2018.
The approval does not expire. Test intervals known from motorsport are a consequence of minimal safety margins in racing wheels, not a property of the material.
Surface
Corrosion protection, documented.
Magnesium requires an effective surface protection system for road use. The protection concept of the mbDESIGN program has been in road operation since 2018; its behaviour is documented under real conditions.
