Only certain, specially formulated, SSs can be hardened by heat
treatment. Most can only be annealed, or softened. All can be work
hardened though, including gold, platinum, etc. Whenever a metal is
deformed, it gets a little harder. Almost everybody has exploited
this property in order to break a wire, or small bar, in the absence
of a suitable cutting tool. You bend it one way, then the other, and
continue bending back and forth until it breaks. Every time you bend
it, it gets a little harder, until it gets so hard that it can no
longer bend without breaking.
This process is called “work hardening”; the bending deforms the
metal which gets a little harder. You don’t have to bend it; you can
twist, hammer, stretch, compress, or deform it in any way you like.
For your money clips you should design the work hardening in from
the beginning. If your metal comes in the annealed (or softened)
state, the easiest way to work harden it is to roll it thinner in a
rolling mill. Even easier is to buy it in the fully hard state to
begin with. By the way, heating a metal to a certain point (usually
around 600C for silver) anneals it and makes it soft again, so avoid
soldering after hardening.
If the metal you want to use has been formulated to be heat treated,
then the suppliers should have full details of the process.
Regards, Gary Wooding