Recrystallization Problem in Aluminum Extrusion

[yirmidokuz]

Hi all colleagues,

I am working in an aluminum extrusion company.
We are mainly manufacturing 6xxx series aluminum profiles, using extrusion processes.

Recently, we received a claim from one of our customers regarding the issue given in the photograph below.

As marked in the photo, there are three layers of grain structure.

1. The most outer layer that is recrystallized and grain growth and has equaxial-like grain type.
2. The quarter diameter that is recrystallized and grain growth and has equaxial-like grain type.
3. The very center layer that has the fibrious grain structure that is expected and demanded grain type.

The problem here is that, our customer do not want the equaxial-like grain structure at the quarter radius of the extrusion.

Do you have any idea to lose that structure at the quarter diameter of the profile ?


*Alloy: 6082
*Condition: T4

 

[EdStainless]

Did it extrude like this or did it happen when heat treated?
If it happened in extrusion you need less energy input (lower temp and/or less reduction).

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P.E. Metallurgy, Plymouth Tube

 

[yirmidokuz]

This one was right after extrusion.

But in some other diameter rods, it happens after heat treatment.

I see this problem even in the low extrusion ratios,eg 13.

I am suspicious about the ram speed. I am going to give it a try.

 

[metengr]

Are the billets used for extrusion homogenized?

 

[yirmidokuz]

@metengr

Yes. They are definitely homogenized.

 

[metengr]

Then you have to look at your extrusion process.

 

[WKTaylor]

yirmidokuz...

I'm surprised Your in-house tests did not reveal this grain structure. Are You extruding in the -O or -W temper?

Suggestion... IF You don't already have them...

ASM has several excellent books on aluminum extrusion technology. The website also has numerous papers and reports available, this subject.

http://www.asminternational.org/tec...mode=view&p_p_col_id=column-1&p_p_col_count=1

The Aluminum Association had [?] a great design guide for aluminum extrusions: I have access to AA AEM-1ENGL 1998 Aluminum Extrusion Manual 3rd ed thru IHS Standards Expert.



Regards, Wil Taylor

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o We believe to be true what we prefer to be true. [Unknown]
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[yirmidokuz]

@WKTaylor

The photo given in the first post was from another extruded rod.
I shared that photo because the variation of the grain structure too obvious.


we are extruding in T4 temper.

... AA AEM-1ENGL...

I couldn't clarify much what that means actually.