That's the problem with bonding the sprockets on. You get the worst of two worlds.

You can't rely on to stay on when you need them to, and you can't count on to come off when you want them to.

Try using heat to weaken the bond. If you have a propane torch slowly heat the sprocket while keeping steady torque on it with a chain whip. Be carefull the melting temp of aluminum is fairly low and unlike steel, it goes very suddenly from solid to liquid.

If you expect to do work with heat a lot you might consider using temperature sticks to help you manage the process.