Heat Treating 6061-T4 without quenching

Hi There,
Here is a question that no one in the industry answered me if I can do it yet. I am building on the side an aluminum bicycle frame. I would
like to heat treat it after welded. All that I have however available in my company is an oven that can heat up to 450F. So all we can is pretty much age it after welding. I know that as per the literature available, after welding you have to heat treat in solution and quench it and than age the piece. Here is the question though, that I will highly appreciate if anyone can answer it: Is it possible to just age the frame after welded let's say 6 hours at 350 degrees. Or is that going to be worse, since I am re-aging a T6 tube and will be in fact over-aging it and make it very brittle. Second question: If that is the
case what would happen if I can get 6061-T4 tubing, weld it and than age it, again without heat treating or quenching it. Would that make the tube actual T6 after welded. What would happen with the actual weldment and annealed area? I am trying to find the easiest way to recover some strength at the joints, without making it worse than not doing anything at all.
Thanks in advance!
Dumont
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If you just artificially age 6061-T6 welded with 4043 or similar, you might end up with around 70% or better of the original tensile strength of the material in the T6 state. The weakest point is going to be where the metal was melted or in the heat affected zone (not melted, but stucture affected by the welding heat) where the base metal has been overaged. Overaging does not make aluminum alloys brittle. It reduces the tensile strength and makes them less susceptible to cracking.
One option may be to use material in the T4 temper and artifically age according to manufacturer's specifications after welding. This should prevent the overaging in the heat affected zone. I don't think you will get optimum strength in the fusion zone because the slower rate of cooling than with quenching will allow some phase change. But it may be good enough.
Of course, the best option is still to solution heat treat after welding then artificially age to get back optimal strength throughout.
BTW you can minimize the overaging in the heat affected zone by minimizing heat input. In other works, use small stringer beads (no weave).
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Great, thanks Metal genius. It sounds like an answer to me. I will move ahead with my project. Thanks again! Dumont
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My server missed the answer! what was it, can you recopy it for me?
Brian

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