Two days ago I found myself staying in Socorro, New Mexico. This is a small town, but blessed with a first-rate college, the New Mexico Institute of Mining and Technology, with about 2,000 boarding students. I spent an hour or so in the new library, perusing the new engineering and technical books.
One which caught my eye was Friction Stir Welding & Processing (2007), by Mishra & Mahoney. I'd not heard of this process, but learned that it was invented in the UK in 1991. It can successfully join materials considered virtually unweldable by conventional techniques.
http://images.google.com/images?q=fr...mages&ct=title has some slides, indicating how the process works. I don't see any reason why it could not be adapted to the home shop. Has anybody had experience with this?
 I should have searched first. I see Evan mentioned this in a thread several years ago. But the book is new, so I will keep this thread, in case anybody has something new to add.