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Grain Size
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Nonferrous topics such as copper and aluminum, annealing, etc. go here.
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TOPIC: Grain Size

Re: Grain Size 2 years, 3 months ago #1616

I've said a couple of times that I am not a metallurgist. I found the following:

The Development of Dislocation Structure and Texture in Rolled Copper (001)[110] Single Crystals
M. Wróbel, S. Dymek, M. Blicharski, and S. Gorczyca
Department of Metallurgy, Academy of Mining and Metallurgy, Kraków, Poland

Received 24 October 1987


The initial orientation has split into two equally strong symmetric orientations: (112)[111¯] and (112)[1¯1¯1]. Areas of identical orientation were band shaped and were called deformation bands. Up to 60% reduction, deformation occurs by slip on one plane (one from two possible) in two directions. This leads to the appearance of deformation bands with transition bands between them. Due to such deformation the initial orientation rotates around transverse direction towards the end-orientation (112)(111). Due to rotation of the crystallographic lattice with deformation, the Taylor factor M changes as well, and it causes the activation of two not coplanar slip systems which stabilize the end-orientations (112)(111). Such a sequence of the slip systems activation was concluded from the agreement of the calculated and experimental pole figures. The electron microscopy investigations showed that first shear bands formed due to the activation of these new slip systems.

From what I have read (again from memory) typical annealed copper has a mixture of 110, 111, 112. Wire that has been through the inline wire drawing and annealing by way of the enameling process has all 112 orientation and as a result has higher tensile strength and lower (better) springback values.

I know in the 60's there was a paper written about inline drawing by BICC engineer. It explained the structure and the results. I also wrote a paper and quoted him. I'll have to dig out a copy.

Re: Grain Size 2 years, 3 months ago #1617

Hi Spectre,

OK I am no metallurgist either but I did take a pretty serious metallurgy course in third year. Dusting off my metallurgy books, I came to this conclusion. I am pretty much out on a limb here so please let me know if I am right.

- Copper has a Face Centered Cubic (FCC) crystal structure meaning that each face of the crystal cube has 5 atoms of copper. One in each corner and one in the center.

- The Taylor Factor is nothing more than a measure of the plastic work required to deform a polycrystalline material and it is based on simple work relationships.

- The numbers you refer to are, I believe, the Miller Indices and these are the inverse numbers to plane intercepts in a single (FCC in this case) crystal. Thus the (112) orientation you refer to is a slip plane at X=1, y=1 and z (vertical)= 1/2 on the FCC crystal in the direction of drawing and that makes a lot of sense to me, recalling Mohr's Circle.

- The crystal structure was somewhat unusually deformed by slow inline drawing but the slow inline annealing process at the enameling oven is inadequate to once again recreate the full FCC polycrystalline grain structure with random slip planes created by various building block errors and impurities. Instead, the original FCC polycrystalline structure remains organized in the deformed 112 slip plane orientation and that modifies the mechanical properties of the metal slightly.

Is that the way you understand it?

Best personal regards,
Peter J. Stewart-Hay
Stewart-Hay Associates

Re: Grain Size 2 years, 3 months ago #1618


Glad you got the metallurgy book out. I was struggling last night with using the wording face centered so I didn't. I think the description you give is correct as the crystalline structure of the wire is all or almost all 112 and as a result also has the altered properties.

For coil winding it is great because the higher tensile strength reduces stretching, and the lower spring back keep the coil from unwinding and losing form.

Re: Grain Size 2 years, 3 months ago #1619


Did you ever come across the term "Single Crystal Copper"? This is the OCC (Ohno Continuous Casting) process from Chiba, Japan. (Essentially a suburb of Tokyo.) We discussed the possibility of manufacturing this copper for very high end audio cables with Professor Ohno in 1987 but decided that it was too much of a piece-work process for us. The whole concept was to produce truly distortion free signals down a single crystal copper conductor. The thousands of grain boundaries per foot of conductor smear the signal somewhat but we were also not sure if the human ear would ever be able to tell the difference. Later as I recall, Sony was marketing headphones with single crystal copper leads.

Best personal regards,
Peter J. Stewart-Hay
Stewart-Hay Associates

Re: Grain Size 2 years, 3 months ago #1620


Prior to Ohno (1984), we provided wire to all of the major speaker/head set manufactures JBL, Koss, Bose, and a couple of others. At one time we were the wire of choice.

I did a web seach on Ohno and found a couple of good sites with equipment drawing and photos of slides at different magnification. One of the sites said that an OCC wire of 0.3mm would be 125 meters long which is probably more that enought for coils in head sets.

From the description of the process it appears similar to a Westinghouse process that was used to make very fine alumimum wire. A sample of aluminum is heated and compressed and a filament is extruded out a defined hole. In our case they were actually sending us 50 awg aluminum wire. Downside was that a big package was about 20 grams. We enamel insulated it.
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