Heat Treatment Effect on Aluminum after Welding

[rb88]

Is it uncommon for welded aluminum not to get a post weld heat treatment due to the quick loss of strength shown in Al?

Could a lack of heat treatment be a cause for weld cracks later in a part's life cycle?

 

[kenvlach]

What is the base Al alloy & its initial temper?
What filler alloy?
What welding procedure?
I don't think it is common at all for aluminum welds to receive PWHT.

Many aluminum alloys (3003, 5052) are basically work hardened -- any heat input tends to anneal them.

Heat treatable alloys (2024, 6061, 7075, etc.) are nearly annealed at the weld. More heating spreads the weakness. Unless you can heat the entire structure to 900 F (solutionize), water quench & then re-age harden at 320 F, forget it.

Cracks may be due to wrong filler alloy, poor weld design, contamination or many other things.

Some sites with info on aluminum welding:

http://www.alcotec.com/

http://www.lincolnelectric.com/knowledge/articles/content/alum.asp

http://www.thefabricator.com/AluminumWelding/AluminumWelding_TechCell.cfm

http://www.harrisproductsgroup.com/consumables/alumfillerchart.asp

http://www.welding-advisers.com/PRACTICAL_WELDING_LETTER-PracticalWeldingLetterNo41B.html

There is perhaps a trend toward low heat input, autogenous, laser welding to minimize effects of the welding. Also, friction welding.