No direct experience here as I mainly do woodwork.

But, looking at it I would say that the bit was either blunt, the wrong type or the feed speed was too slow and it has melted/ welded the cut rather than cutting cleanly and clearing the chips.
A 1mm endmill with 2 flutes leaves little room for clearing waste maybe try a single.

What does the endmill look like now, does it have aluminium stuck to it ?

I am sure someone will be along with a comprehensive answer shortly.

Ollie