Which alloy is currently used? There are several BeCu alloys.
Depending on the Yield Strength requirements, there are several bronze and Cu/Ni/Si alloys that are being utilized.
Most copper alloys used in spring and connector applications can withstand Stress relaxation under 100 degC.
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Polymat:
I have info on an alternate material that performs very much like the C17300. It is marketed for your application.
I could refer you to the manufacturer
Steve Ross
rossmetal@sbcglobal.net