Can someone explain the process?
It's easy to cold weld stuff together in vacuum chamber at 10^-8 torr; just clean everything well so that the metal is clean, put the parts in contact with some pressure, and leave them under vacuum for a few days.
If they are made of the same alloy the may cold weld. The cleaner the quicker, and more pressure also helps.
Too avoid this use aluminum; the surface oxidizes so quickly that you will always have a layer of aluminum oxide. Or use two different metals. Or spread a light coating of molbdenum disulfide between them ... dry moly.
I've had this happen with my vacuum fixtures ... and learned my lessons! The article above has a good Feynman quote.
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