this post was submitted on 15 Jul 2025
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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/

explainxkcd for #3115

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[–] Successful_Try543@feddit.org 68 points 1 week ago (1 children)

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

[–] Lemminary@lemmy.world 4 points 1 week ago

Oh, but of course! The deviatoric strain, yes.