Really quite a lot.
For both much of the engine and many of the high load extruded structures, the Spitfire used an Alloy developed by Rolls Royce called Hiduminium, a portmantau of High Duty Aluminium.
There were quite a few versions of the RR alloy and it was RR.56 that did a lot of most challenging work in a Spitfire. This was an aluminium alloy that used around 2% Copper, around 1% of Nickel, Magnesium, silicon and Iron and a trace of Titanium. However, the sheet that makes up almost all of the shiny you can see above is pretty close to pure aluminium, although this just a protective coating on L.72, which is a Copper, Magnesium Silicon Manganese alloy. Although as the spitfire above is a recent rebuild it almost certainly isn’t that as this alloy, at least, has generally been overtaken by newer alloys.
The Zero
on the other hand, used a highly secret and, recently -at the time - discovered alloy that was introduced as extra super Duralimin, but is now know to the world as 7075 and has been used in some of the most extreme situations, for example in the Space Shuttle! This alloy uses getting on for 6% Zinc, over 2% magnesium, around 1.5% Copper and small amount of a range of other elements. Depending on how it was tempered it could be used in a surprisingly wide range of applications. The only real issue with it was poor corrosion resistance, which is why you don’t see polished Zeros often, or for long!
There’s a Zero in The Imperial War Museum in London that has always entranced me with its moth-like fragility:
It’s just luck that Japanese engine technology lagged behind the allies by just enough. Parity in horsepower and a few modifications to improve survivability earlier in the war and the balance of power could have looked quite different…
