the heat treatment of the finished part helps make for a less bendable length,
a mix of ductility and hardness, made by Heating and Quenching when that heat is reached ..
OP got a cheap Folding biker ,maybe he will send a picture..

Copper is a Non ferrous metal , piping is sold annealed for plumbing, to be flexible for fitting.
so a weak example .. metallurgical apples v oranges
when comparing with a tempered steel alloy., or high strength say 7075-T6 Aluminum.