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Copper is very ductile (soft) compared to many other metals because it is molecularly arranged in a cubic arrangement, while other less ductile common metals te

Copper is very ductile (soft) compared to many other metals because it is molecularly arranged in a cubic arrangement, while other less ductile common metals tend to be arranged hexagonally or are alloys of multiple elements. The mono-elemental cubic arrangement has more horizontal planes. Horizontal planes of molecules can 'slip' past each other more easily, and in the electron soup that characterizes metal the bonds between those molecules can more easily "stretch" without breaking. This is why you'll find ceramics with a cubic structure that are brittle and prone to breaking in layers, rather than being ductile. It's also why metals are great conductors! If you like this kind of stuff, check out introductory undergraduate level 'materials science' course materials! There's tons of lectures and educational content on YouTube and textbook PDFs are bountiful on the net :)

bityard 5y ago
Yep but copper does lose ductility when deformed. When put under enough stress to deform it, it "work hardens." This is why thick copper wires break if bent back and forth too much (and hence why we have multi-stranded wires for applications with movement and vibration), and why crush-sealing washers can't be reused. This work hardening can be undone by heating the copper until it gets red hot, but this isn't practical in many applications.
- MisterTea 5y ago
  I was under the impression crush seals are used once not because of work hardening but from deformation. You can only crush them into place once. e.g. on conflat vacuum flanges the harder stainless steel knife edge on the flanges sandwich the copper gasket biting into it creating a tight metal-to-metal seal. That biting plastically deforms the copper forcing it into the tiny surface imperfections in the stainless to form an extremely tight seal. Once you break that formed copper seal it is permanently damaged. It cannot be reused as the mating area has has been deformed and the majority of its material squeezed away from the mating area. You have to start over with a fresh flat seal that will deform into the cracks and crevices.
  - bityard 5y ago
    You're totally right, it depends on the application. I was thinking of oil drain plug washers, which can be reheated and reused many times, basically until they are too thin to do the job.
    - pengaru 5y ago
      I usually just sand the washer surfaces flat on some high (600-800) grit wet-dry paper, never had a problem. Works on banjo bolt washers too.
MisterTea 5y ago
My father was a metallurgical engineer though unfortunately passed away when I started high school. Recently after reading a story on melting iridium in an e-beam furnace I am now finding myself fascinated by metallurgy. One thing that interested me is the seemingly simple yet complex process of vacuum metallurgy where alloying and/or purifying is done in a vacuum using all sorts of exotic heating and handling methods.
- sitkack 5y ago
  Not a metallurgist, but it really seems like zero-g alloys will give us some amazing materials. https://www.google.com/search?q=zero+gravity+alloy+site%253Aedu https://www.google.com/search?q=zero+gravity+alloy+site%253A...

bityard 5y ago

Yep but copper does lose ductility when deformed. When put under enough stress to deform it, it "work hardens." This is why thick copper wires break if bent back and forth too much (and hence why we have multi-stranded wires for applications with movement and vibration), and why crush-sealing washers can't be reused. This work hardening can be undone by heating the copper until it gets red hot, but this isn't practical in many applications.

MisterTea 5y ago
I was under the impression crush seals are used once not because of work hardening but from deformation. You can only crush them into place once. e.g. on conflat vacuum flanges the harder stainless steel knife edge on the flanges sandwich the copper gasket biting into it creating a tight metal-to-metal seal. That biting plastically deforms the copper forcing it into the tiny surface imperfections in the stainless to form an extremely tight seal. Once you break that formed copper seal it is permanently damaged. It cannot be reused as the mating area has has been deformed and the majority of its material squeezed away from the mating area. You have to start over with a fresh flat seal that will deform into the cracks and crevices.
- bityard 5y ago
  You're totally right, it depends on the application. I was thinking of oil drain plug washers, which can be reheated and reused many times, basically until they are too thin to do the job.
  - pengaru 5y ago
    I usually just sand the washer surfaces flat on some high (600-800) grit wet-dry paper, never had a problem. Works on banjo bolt washers too.

MisterTea 5y ago

My father was a metallurgical engineer though unfortunately passed away when I started high school. Recently after reading a story on melting iridium in an e-beam furnace I am now finding myself fascinated by metallurgy. One thing that interested me is the seemingly simple yet complex process of vacuum metallurgy where alloying and/or purifying is done in a vacuum using all sorts of exotic heating and handling methods.

sitkack 5y ago
Not a metallurgist, but it really seems like zero-g alloys will give us some amazing materials. https://www.google.com/search?q=zero+gravity+alloy+site%253Aedu https://www.google.com/search?q=zero+gravity+alloy+site%253A...