Technical term for Tin disintegrating at cryogenic temps. 1

[59133]

Can someone forward to me the technical term for the disintergration of pure Tin when exposed to temps at -50 deg. Celsius in air? Can this type of thing happen when in vacuum? Can this happen when the Tin is in an alloy of Tin/Lead solder?

 

[Carburize]

The phenomenon is known variously as "Tin Pest", "Tin Plague" or "Tin Disease" It is caused by an allotropic transformation of tin from the normal white metal tetragonal structure to a grey powder cubic structure. The actual equilibrium transformation temperature occurs at 13.2 Degree C but significantly lower temeratures are usually needed in practice for it to take place.

 

[59133]

Thank you Carburize. You wouldn't happen to know if this happens to Tin when it is an alloy or does the alloys present with the Tin inhibit this allotropic transformation?

 

[SMF1964]

For thought: if the addition of alloying elements to tin results in a strain to the atomic lattice or an outright change in the atomic crystal structure to some other structure, would it not be the case that the mechanism in question ('tin pest') would be retarded or eliminated completely?

 

[59133]

Thank you SMF1964 for your thought. Here is another thought. What if the Tin is not fully alloyed and there are pockets of Tin that have precipitated out. Will not these pockets of Tin fall prey to the same 'Tin Pest'? If so, the next thought is, what kind of an affect will this have on the thermal performance of the alloy with the pockets of 'Tin pest'?

 

[Carburize]

I believe that very low levels of additions prevent the mechanism. If my memory is correct I think that 0.1% bismuth has been added to tin and solders for many years in order to guard against the change even after extended exposure to low temperatures.