When one of my wife's poles was badly bent as it was tied to the outside of the checked luggage (and the flight company said, tied to the outside would be no good for an insurance case) we went to the shop we've bought it and the guy opened a drawer full of used pole sections we could select one that fit.
If you bend back a bent Aluminium pole, all sorts of things can happen and the higher the materials strenght the worse, but none would make the piece near as good as it's been originally.
If one has to rely on the poles seriously, its highly recommended to replace the bent (and bent back) piece eventually.