The Advantages of Magnesium Alloy Integral Wheels

Some riders still feel unsure about magnesium alloy, so here is a short discussion of this popular new material: how good is magnesium really, what applications has it already reached in cycling, and where is it heading?

Magnesium versus other alloys. The material most riders know best is aluminium alloy. In reality China holds only 2.96% of world bauxite reserves — ninth in the world — and imports large quantities every year. At current rates of development domestic bauxite could be exhausted within about ten years, and long-term dependence on Australian imports adds uncontrollable risk: the price is set by the seller, and a political dispute could threaten supply at any time.

So what replaces aluminium when it runs out? Magnesium is one of the most abundant light metals on earth, and China is one of the richest countries in magnesium resources, holding 21.7% of world reserves — first in the world — and is the largest exporter of magnesium.

The density of magnesium is only 1.74 g/cm³, about two thirds that of aluminium, two fifths that of titanium and one quarter that of iron. Magnesium alloys — magnesium with other elements added — are 36% lighter than aluminium alloys, 73% lighter than zinc alloys and 77% lighter than steel, while elongation and impact resistance are clearly better than die-cast aluminium alloy. Compared with typical structural metals and engineering materials, magnesium alloys offer a very favourable strength-to-weight and stiffness-to-weight ratio, making them particularly suitable for lightweight structures. They have a high modulus of elasticity, good rigidity and strong vibration damping — 30 times that of aluminium alloy — and they withstand impact loads better.

Magnesium alloys also have very high die-casting productivity. Like die-cast aluminium and zinc alloys they flow well; their latent heat of crystallisation and thermal conductivity are lower than A380 and their freezing range is wider. Filling ability is therefore good, solidification after filling is fast, thermal shock to the die is small, thin-wall parts can be cast without hot tearing or under-casting, die life is extended and the casting cycle is shortened — die-casting productivity is about 75% higher than with aluminium alloy.

Beyond this, magnesium alloy conducts heat well and resists attack by organic substances and alkalis — completely unlike pure magnesium, which is flammable, unstable and highly reactive.