+1 on Roger's cautionary advice. Leave the metallurgy (heating etc.) to the pros.
Fabricating with metals is another matter. 6061-T6 is a good metal for bending if the walls are thick enough for the strength you want. The stock is sold in metal displays in many good hardware stores.
Not clear from your statement of the dimensions what they are. Tube dimensions are not like lumber where the description is standard and just numbers can be provided. It is helpful to use "D" for diameter, OD for outside diameter, and if the number is for wall thickness, so state. From your OP, I'm guessing this was 1/2" OD, but just guessing.
Before getting too deeply into the bending process, you might want to consider just buying the U-shaped frame sold by GG at: http://gossamergear.com/packs/aluminum-curved-stay.html
It is $25 US, but might end up being cheaper than buying a DIY setup, not to mention the time saved.
If you decide to go ahead, a tube bender is critical, because it holds the walls of the tube in their circular shape during bending, so the tube does not flatten or break. The best ones I've found for home use are the Ridgid brand. But much cheaper ones are available from the online hardware companies, and so long as they are tube, and not rod benders, they should be good for a small job or two.
It is also helpful to pack the tube with fine sand before bending. Hardware stores have flexible plastic tube caps for furniture and other apps that will hold the sand in place. Be sure to tamp it down well in the tube so it is packed tight before capping and bending.
Using the above, I've bent ALU ski poles more tempered than T6, and thinner than the hardware store stock, to a radius about the same shown in your photos. Most recently, for a lightweight camp chair - thread posted this September on this site.
I'm working on a frame now made of ~3/8" OD T9 tubing that will not bend to a 2.5-3" radius, so obtained ferruled prebent elbows from Quest Outfitters, and bonded with JB Weld suggested by Dale W on this site, which is sold in Walmart and proved a terrific adhesive for ALU tubing. The T9 can be bent to a larger radius, but won't go there as it is not your issue.
Bending or elbowing the tubing has a much cleaner appearance than using Tee or L fittings, but if you want to go there, you can spend a lot of time at plumbing supply departments and stores looking for what will fit the tubing sizes you have available. There are also kite fittings, but most are made from a rubbery material that does not handle stress well, and almost never fails to disappoint. Been there. Drilling holes in the smaller diameter tubing to hold the fittings in place is not recommended for reasons you don't need to be a metallurgist to grasp. So then you have an issue of finding an adhesive that will bond the ALU and whatever type of plastic the fitting is made of - not so easy to find, given the different materials. You might have to settle for a very tight press fit.
So there are some approaches that I hope will be helpful.