Aluminum frames in general can't be re-welded or reformed without a significant process of heat treatment. So, yes, a really good welder might be able to get in there and weld, but unless he has the ovens to bake the frame (and this takes hours/a day) the joint will never be that strong, and unless he has superbe atmospheric conditions in his fab, re-welding aluminum is very difficult on jagged breaks. You need to start with very clean aluminum which is rapidly welded right after cleaning to prevent oxide from forming on the exterior which I here creates micro-fracture sites in the weld that will fail again.

Hope you're okay and didn't suffer physically. Let us hear about the warranty.