Malleability and bending of metal at cryo temp

[uWave_Matt]

I think the broadest way to frame this question would be as follows:

"If a metal conductor (copper wire) were bent at room temperature, then placed in a cryo-cooler and cooled to ~30-80 kelvin, would it experience any 'unbending?'"

More specific to the situation, I've bent down the center conductor of a coaxial cable (very slightly) to act as a probe to a piece of superconducting circuitry secured in a jig, and pumped the chamber down. Is it possible that, at superconducting temperatures, that the probe loses malleability causing it to become more rigid and thus, straighten?

I apologize for my limited understanding on physical properties of metals. My only real exposure to them is from an introductory MEMS course.

Thanks for any feedback that you can give.

 

[Q_Goest]

Hi Matt,
The copper wire will remain bent in the position you bend it. There are stresses imposed in the material that will remain in the material regardless of how low a temperature you go. They don't relieve themselves and cause the material to change shape. The copper will shrink as I'm sure you're aware, and the modulus of elasticity will increase slightly, but it won't change shape because of stresses that are created in the material due to bending.

If you need any information on material properties at low temperature, post here or in Materials & Chemical Engineering forum.

 

[AlephZero]

You might have half-remembered something about "smart materials" which do "straighten out" and then return to their bent shape as the temperature rises and falls.

That only happens to specially "designed" alloys with a particular type of internal atomic structure, not to materials like copper wire which is almost a pure single chemical element.

 

[uWave_Matt]

Hi Matt,
The copper will shrink as I'm sure you're aware, and the modulus of elasticity will increase slightly, but it won't change shape because of stresses that are created in the material due to bending.

Perhaps the shrinkage is significant enough to cause loss of contact and I was trying to over-complicate it. It'll go down in the lab notebook and thesis as "possible explanation."

Thanks to both of you for expelling this unbending business from my mind.

 

[AlephZero]

Perhaps the shrinkage is significant enough to cause loss of contact and I was trying to over-complicate it.

Thermal expansion coefficient of copper = about 17 x 10^-6 / K

So if you are cooling from 300K to say 50K, the "shrinkage" will be about 0.4% of the original length.

Of course the interesting number is the difference between this and the shrinkage of the other parts of your test rig, not the absolute value.