Question

Why don t tiny cracks heal in metal via cold welding?

Answer 1

♡●BONJOUR●♡

⬇️HERE IS YOUR ANSWER⬇️
________________________

Two reasons:

1.Oxides
2.The roughness of the surface

If the surface is rough, then the majority of the surface is touching the air gap between the two, not the opposite surface. A bond may form at the touching "peaks", but it will be weak compared to the rest of the metal because a very small fraction of the surface has actually bonded.

In addition, metal surfaces adsorb oxygen and form oxides/oxygen monolayers on the surface. This is actually a visible process with metals like sodium and potassium (the color changes in a short time period). But for all metals, there still is oxide formation to a sufficient extent, because the edge metals have not completely fulfilled their valencies. Even a monolayer of adsorbed oxygen is enough to stop the surfaces from welding.

If two clean, flat metal surfaces are brought together (usually in a vacuum), they do indeed cold weld. This is hard to achieve for macroscopic objects because of the perfect flatness requirement, but is still possible. In practice, it is more commonly used for welding small things.



HOPE THIS ANSWER HELPS YOU
MARK AS BRAINLIEST ✌✌
_______×××××_______