Metal Springs in Liquid Nitrogen?

I need to build an apparatus in which a spring is used to press two parts together, then the entire apparatus is immersed in liquid
nitrogen. I expect the spring to shrink when cooled, of course, but I hope I can find a spring that will contiunue to behave more or less like a spring when cooled to 77K (-196C, or -321F). Any suggestions?
Also, what effect will this sort of thermal cycling (room temp, liquid N2, back to room temp) have on Aluminum, Copper, and Lead? Are there any metals that I should specifically avoid using?
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Please reply to: | "When the press is free and every man
pciszek at panix dot com | able to read, all is safe."
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Paul Ciszek wrote:

Steel becomes brittle at low temperatures--the harder, the higher the temperature.
Cheers,
Phil Hobbs
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Phil Hobbs wrote:

Only bcc steels.
Michael Dahms
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Paul Ciszek wrote:

No effect in pure fcc materials.
Michael Dahms
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Springs made of Austenitic stainless steels such as AISI 301, 302 etc. or springs mafe of BeCu alloys such as CDA 170, 172, 175.

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I think copper alloy is the best material. like Cu-Be alloy
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