What metal is the outer 'bell' of drone motors made of? And why?

[Yorkshire_Pud]

I have seen one or more posts on the DJI forum (prossibly laughable posts) speculate that in the much talked about possible Mini 3 the metal is Aluminium. It 'got me' to wondering, is that likely?
I don't remember enough from my schooling to know if it would be better, magnetic-field-'management'-wise, for it to be made of a magnetic metal but, and specifically applicable the the Minis, would the female screw threads used to mount the prop blades be durable enough it the bell were made of Aluminium?
Would Aluminium have the strength to withstand the 'hoop stress' created when the motor is running at 1y,000 rpm?

 

[old man mavic]

well as weight is a big consideration ,then i think it is safe to assume that the rotating parts of the motor are made of some form of aluminum alloy ,what the proportions are is up to a metallurgist to determine

 

[Gagey52]

Different suppliers have different ‘recipes ‘ for the customers use.
Regards