The modulous of elasticity for most grades of steel is the same
(29x10^6) What varies is the amount it can be bent before it takes a
permanent set in the new shape. So you are looking for a steel with
high yield strength.

I'd suggest heading to the local hobby shop or well stocked hardware
store, ask for 'music wire'. It comes in 36" lengths, can be bent to
take a shape, is about as springy as you can get without special alloys
or special heat treating. Make the shape you are looking for, see it the
music wire will do the job for you.

If so, your local wireform place can make them by the million very cheaply.

David Lesher wrote:
I'm envisioning a gadget I can see a use for....

It would be made from spring steel, say coat-hanger diameter, in s
specific shape. Key to its use would be it could be bent in one way to
deploy it, but it would revert to its original shape.

What controls how much it can be bent without altering the final shape?

How is such made? I assume it's a combination of steel formulation and
post-manufacture heat treating; true?