Originally Posted by dsaul

7005 frames can be welded and aged at room temperature for a month or so to recover most of its original strength. 6061 requires post weld heat treatment to return it to anywhere near its original strength. If the repair is in a low stress area or a low risk area, such as chainstay or rear dropout, a repair may be successful without post weld heat treatment. I would not risk welding anything in the head tube area. A failure of a chainstay or dropout may cause a crash or just an inconvenient walk home. A failure at the head tube is most likely a trip to the hospital or possibly death. This is not a place for opinions, metallurgy is a science and these things have been tested by people who specialize in that science.