After driving for a little while, you turn into a parking lot, park your car, turn it off and get out. Then you hear the engine making clicking sounds. It only does it when it’s hot, does it have something to do with metals expanding when they’re hot or?
In: 414
Unfortunately, this isn’t very eli5, but what’s going on is something called twinning. When the engine starts cooling, it contracts from the temperature change, which stresses the material since it’s constrained in certain shapes. The clicking is actually due to twinning of the atoms, where the atoms suddenly arrange in a mirror image pattern across a plane in order to relieve stress, and this transition makes the clicking noise.
Source: materials science phd student
https://en.m.wikipedia.org/wiki/Crystal_twinning
https://en.m.wikipedia.org/wiki/TWIP_steel
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