xkcd #3115: Unsolved Physics Problems
Title text:
‘Tin pest’ makes more sense to me. Tin just doesn’t want to be locked down in a shape like that. I get it. But why would any metal want to grow hair??
Transcript:
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Source: https://xkcd.com/3115/
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Metals are crystals so why wouldn’t they grow hairs? Probably just stray electrons and alignment issues lining up. Crystals do things, what’s the big deal?
A colleague of me did his PhD exactly on the last topic.
And does he know why? I’ve had to deal with it too often and it would be really nice to be able to expand RoHS to aerospace.
Deep in the coating, where the Cu6Sn5 [Remark: intermetallic phase of Sn coating and Cu substrate] is present, the deviatoric strain was high. This indicates that the growth of the intermetallic phase causes plastic deformation of the tin coating.
[…]
A short (4 micrometre) radial gradient in hydrostatic stress was observed around the root of the whisker. This gradient together with long-range diffusion from specific regions could provide the driving force for whisker growth.https://portal.research.lu.se/en/publications/tin-whiskers-experiments-and-modelling
Oh, but of course! The deviatoric strain, yes.
I thought long hair was a requisite for metal, especially headbanging.
That settles it. Nobel prize incoming.
