Hey NeoTech,
I saw the pictures you posted and said, "Ooh, ooh, I know what that is!" I rushed to join this forum and raise my hand but it took a few days to get it done so I'm late but would like to agree with jiihoo and udimet. That pattern is one I know well, having done them my very own self!
Basically, you have too fast a feed rate, too slow a cutting speed, and too shallow a depth of cut for a chipbreaker insert. Feed rate for this insert should be, as jiihoo pointed out, about 1/2-2/3 the nose radius (0.02-0.026mm/rev). Cutting speed for aluminum with a carbide insert is faster than the top speed of your lathe so it needs to run at least that. DOC for a chipbreaker insert depends on the manufacturer's recommendation but in general should be about NR+0.020".
While I agree that HSS tools would work really well for you there is that little hump of learning to grind them. It isn't difficult but you still have to learn it, and while I think its a good idea I can certainly understand why you went with carbide. Lots of us do it for the same reasons, myself included once upon a time. If you stay with carbide, which is far more expensive than HSS in the long run, I agree with udimet that going to a 0.08mm NR would be a good idea and only because it will finish better for you. I am not familiar with the Sandvik series you are using but if they offer a flat top insert to fit your lathe tool instead of the chipbreaker one you are using then that will lower cutting forces and greatly aid in both roughing and finishing at lower speeds (reduced deflection).
On the other hand, HSS tools should not cost much on ebay. If you use 1/2" bits you can do with the imports until you learn to grind them well and then invest in some higher quality bits. In fact, I suggest using mild steel keystock to learn on and go to HSS only when you are confident that you can grind what you intend.
Sorry I was so late to the dance and I hope this helps. You've gotten some solid advice from the others - I would take it.
Mikey