Heat Treated Aluminum 2

[dik]

Another thing I didn't know... as I age... these things keep cropping up...

"It must be pointed out that the heat-treatable aluminum alloy will naturally age hard. That is to say that if no further heat is applied to the alloy, the alloy will naturally age to its maximum mechanical properties and hardness. This will take time, ranging from a few days up to years to complete at room temperature, depending on the alloy composition/type. In order to accelerate the aging process, therefore, heat is applied to the solution-treated aluminum alloy."

I don't know if this is true... quite different than what I understood.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[3DDave]

I don't know about climate change, at least to where I can affect it much.

Room temperature aging generally gets to 70-80% of the properties available by heat treatment, or so the materials guy told me. Otherwise, if age-hardening alloys are left in the annealed condition at room temperature they will harden up. This is the reason "refrigerator rivets" can exist. They harden up in minutes from the freezer. Gotta be quick.

 

[EdStainless]

I always was told that they would reach 60-90% of strength, and there is no way to know what you will end up with.
When one part reaches 85% quickly, and the one attached to it reaches 60% but much latter you can get some messed up results.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[dik]

Thanks... I thought the loss of strength due to welding was permanent... learned something today...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik

 

[BUGGAR]

And then there is strain hardening.

 

[r13]

dik,

As you haven't aged enough, here is a Q&A blog you might be interested in reading Link

 

[Compositepro]

A knowledge of steel heat treatment can really confuse you when it comes to aluminum alloys.

6XXX alloys are age hardened. Heating to 900F+ does a solution anneal, which means that all the ingredients are completely dissolved. A quench results in a soft condition where there are no grains in the metal. Grains form with time at room temperature (natural aging), but slowly. Heating at 350F+ will "artificially age" the alloy in about 6 hours. This results in grain growth which greatly increases the yield strength of the alloy. If the grains grow too large the alloy will get weaker again. To recover good properties you must repeat the solution annealing and the aging. Welding these alloys results in the melted material having a significantly lower yield strength than the rest of the metal.

The other series of aluminum alloys behave very differently.

 

[dik]

Another thought... if 6061 is not heat treated... does it just remain as it was?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[drawoh]

dik,

This is a cool thread. Steel metallurgy was about 95% of my college metallurgy. Aluminium has been about 95% of what I have specified on drawings. I have archived this thread.

I sort of expected this. 6061-T6 is artificially aged. This implies that it can be aged non-artificially.

--
JHG

 

[dik]

What if it's not T6? not heat treated... does it just remain as it is?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[r13]

dik,

I think you need elaborate your question to weed out confusions, at least for me. For any metal is not heat treated (no work done), it remains as it was, isn't it? But I think your question is more than this.

 

[dik]

No, it's that simple.. if 6061 is not heat treated, does it undergo any changes over time? I wouldn't think so, but don't know.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Compositepro]

The 6061 alloy must be melted at some point in order to be created. If you quickly chill the alloy to room temp it will be in the soft -O condition. This will then age naturally (-T3,-T4), getting harder and stronger with time. Or it can be heated to about 350F to artificially age it to greater strength in much less time(-T6)

https://llfurnace.com/blog/types-of-aluminum-heat-treatments/

https://materialsdata.nist.gov/bits...of Aluminum Alloys.pdf?sequence=3&isAllowed=y

 

[dik]

Thanks very much... a bit surprising, but good to know...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Ron]

@dik....
The shapes we use for structural work are usually 6061 or 6063, both with a T6 temper. This is essentially the "terminal" temper of both alloys, though there can be further treatment to enhance some properties. In general, both are extruded to a T5 temper and then transition to a T6 temper with aging.

The aging is relatively short to achieve the desired properties.

The reason for the large reduction in allowable stresses within 1 inch of a weld is that the end result of the properties at the weld and the heat affected zone is not predictable. It depends on the welding process, the amount of heat input, the cooling temperature, the cooling rate and other variables.

Does the area around a weld remain at lower strength? Not likely, but it also might not achieve the original properties.

 

[dik]

Thanks, Ron... I have a small project where they have asked for a small frame to be welded consisting of BAR 6061 material. There is no indication of the type of 6061 material, if heat treated or otherwise... similarly there is no reference to post heat treating... Just looking for the 'holes' in this frame. Anchored to concrete with SS Hilti anchors with a smooth isolated bearing surface.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[GregLocock]

"Does the area around a weld remain at lower strength? Not likely, but it also might not achieve the original properties."

Yup, mig welded butt jointed T6 spaceframes show visible softening in use. The first 6mm or so plastically deform.

Cheers

Greg Locock


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