Aluminium? Maybe.
Titanium? Definitely.
But I never would have thought of magnesium as a material for shaving brushes.
Maybe that is because (despite being trained as an aeronautical engineer and having worked for many years as an airline pilot) I still associate magnesium with chemistry classes and its violent reactions to water.
I also noticed that is seems to tarnish badly.
If not steel, my money would be on titanium, but that is notoriously difficult to work with and is probably not practical for a DIY project,
B.
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.
Bertrand Russell