they are screwed togther. all you can do it keep trying, I used some rubber hose on each side, put it in a vice and worked it back and forth , took all day but I got em apart without damaging them. Alum corrosion is like concrete.
if you get em apart, apply woody wax liberally when you put them back togther, soak the ends and the parts that insert into each other good and hose clamp a 3/4 peice of hose over the seams. They will never get stuck again.