If the tube is going into a "socket", rough up the end of the tube and the inside of the socket and use JB Weld.

I make ALL my wing struts from K&S aluminum streamlined tubing using JB Weld and have not had a single
failure. I have had a couple of "unscheduled landings" that have turned the struts into pretzels - the JB Weld
joint was still intact.