If the aluminum handlebar stem is stuck, you can throw away the fork.
If the aluminum seatpost is stuck, you can throw away the frame.

I've dealt with enough of these aluminum-bonded-to-steel nightmares to know that it simply ain't worth it to waste a week attempting to cut, smash, and twist a seatpost free of a common frame such as this Voyageur 11.8.

I only bother to do it on 531 and better frames, for I have a very hard time finding these. In comparison, I can buy a handful of the Schwinn 4130s locally, if I cared to do so. It's probably cheaper for you to buy a complete one locally then to have this klonker shipped to you.

I don't even waste my time attempting to get stuck aluminum stems out of a fork, 531 or otherwise. This is, frankly, an impossible task, unless you care to have the remainder of the aluminum machined out of the steer tube. I simply cut the necks off, take the fork out, and trash the fork. Don't think that you can twist the stem out - you'll soon find that the stem will twist the fork out...and about.

-Kurt