Sunday 18 March 2007

Shaping copper

I thought I'd hate inorganic technology. But it is one of the coolest labs I've ever done. If you know anything about inorganic technology, you can skip this post. But if you think of metals as one big homogeneous phase (like I did) then you may want to take a closer look at metal microstructure.

Normally I am kind of sad that I spend so much time on lab reports that only one person will ever read. So I am happy that I can talk about it a little bit here.

What we did is compress copper and look at its grains. The interesting thing is that all the properties change with rolling. Especially the hardness increases. If you heat it up you can undo parts of those changes depending on temperature and time.

This is the copper as we started out with it. You can see a few large grains. The black spots are Vickers hardness imprints.

If you compress the thing by 30% you notice that the grains are looking in the same direction.

60% compression and everything looks the same direction.
85% and everything looks pretty flat.

You can't roll grains that are flat like this. So what do you do if you want the plate even thinner? Heat it up to 673 K, leave it there for 0.9 ks [1]. And you can pretty much start over again.
To get images like these you have to cut your sample with a diamond saw. Then you have to grind and polish it with SiC and diamond. After that we etched the surface with FeCl3 and took pictures with a microscope that has a camera attached to it.

[1] It's important to always use SI units at all costs.


Ψ*Ψ said...

I've never done a lab like that. Maybe the engineers here do? Either way, I usually just think of metals as "icky."

Anonymous said...

What instrument do you use to take those photos?


Felix said...

this lab really changed my view of metals, I have to say

I guess I should have mentioned how we made those pictures. I just added that