Despite the name, JB Weld has nothing to do with welding. It's a reinforced (and colored) epoxy resin. It doesn't have nearly the strength of aluminum, so unless reinforced with fiberglass or the like, or built up damm thick it won't natch the strength of the tube that failed once already.

Also it's elastic properties may not match that of the post within well which will cause the job to fail sooner rather than later.