This is true, and I should have been more clear in my wording, but I was referring to heat treatment after machining.Netpackrat wrote: ↑Tue Jan 25, 2022 12:02 amSome of the most common alloys are heat treated. Say you make something out of 6061T6, the "T6" is the temper designation. It comes from the mill with all the heat treatment it will ever need (or benefit from). If you ever get your hands on a piece of 6061T0, you will be able to tell the difference, especially in thin sections. In aviation we're usually working with 2024. The normal way it is supplied is in some form of T3 or T4 temper, which again is the heat treated state (with some minor differences between the two and other designations besides). Occasionally we will need to make a repair part with some significant forming operations which would result in cracking if done to material in the T3/T4 condition. In those cases, it's common to start with T0 material, do the forming operations, and then have the part sent out for heat treat. The T0 material is very soft and wouldn't be useful for much, aviation or otherwise.Vonz90 wrote: ↑Thu Jan 20, 2022 3:07 pmI don't do aero stuff so maybe the aero guys can chime in, but at least in the part of the engineering word I live in, I have never seen a need for heat treatment of anything aluminum that I have designed. There are some alloys that can theoretically be heat treated, but it is not common.
Other alloys are not heat treatable, and reach their full temper through work hardening. These are common in marine environments for example (5083/5086, 5052), and sometimes in aviation for non-structural parts (tanks, fairings, etc... Generally 3003 or 5052). The door, bonnet, and boot lid skins of my MGA are made of 5052. Part of the panel beater's art is to arrive at or near the desired hardness at the end of forming operations, since the only heat treating process available with such alloys is annealing. Depending on what you are making, and how severe the forming operations, you might need to anneal several times before the part is completed. You don't want to have to anneal again as you are just finishing because then the part will not have its full possible temper, but if you don't anneal enough you could get a crack somewhere in the process.
The reason for that, is if you started with something like 6061T6, after welding you might have something closer to T2. That might be strong enough depending on the application, but if heat treating is specified, the purpose is to restore the temper that the material originally had prior to welding. Some alloys (such as 2024) are not generally considered weldable.blackeagle603 wrote: ↑Mon Jan 24, 2022 8:45 pm Yeah, only time (in my sphere) I've seen aluminum heat treated was after welding.
I suppose heat treatment after welding makes sense, but if (or one of the engineers working for me) ever designed an assembly requiring welding aluminum, I would think again and do something else.