Post weld tempering of aluminium alloys

[Blastertrev]

Sorry not to have been posting much for a while, but been busy getting on with welding! I'm now managing to do competent welds in 6082 T6 extrusions, however I'm having issues with loss of strength post welding on some items where there's a lot of welding or welds close together. I roughly know the theory of tempering aluminium, does anyone have any experience of tempering work pieces after welding, and how effective is it? Thanks.

 

[TechnicAl]

Its hardest condition is as wrought. All the heat treatments are designed to temper it from the wrought condition.
http://www.fairdene.com/chimera/materials specs/alloy 6082.pdf

If you wanted you could heat treat the whole lot as per the temper designations. If they are harder than what you have, which isnt a certainty

 

[Engineer]

Heat treatment is very effective, and is what makes it viable to produce cycle frames using lightweight aluminium tube sets. However its not something that can be carried out on a DIY basis, and you will either need to find someone able to do this work for you, or increase strength through using thicker or higher spec material.

 

[hotrodder]

They get the T6 temper by a solution heat (heat to 575ish C to take the alloying elements into solution) and quench (need a very high cooling rate to prevent the alloying elements precipitating out of solution in an uncontrolled way) and then artifical aging (a low temp bake around 175C for around 8 hours is typical for 6082-T6) to get the desired properties

Weld 6082-T6 and you get different 'zones' near the weld depending on the temps reached. Post weld artificial aging can improve things for some areas but not areas that end up 'overaged' and of course areas unaffected by the welding will be put through another aging treatment and become overaged. Overaging decreases hardness and toughness but i think it tails off relatively slowly i.e. properties quickly improve in the first hours, slow down and peak and then slowly trail off.

If you were to post weld age you should see a little improvement in hardness but it'll likely be inconsistant and the response of the weld metal will depend on dilution as 4043 itself won't respond. If we're talking something small enough to fit whatever oven is to hand then i'd say have a play with 2 or 3 hours at 175C, without hardness testing kit i doubt you see a difference though