Your aluminum fork had a tapered piece added to the crown race seat in order for it to have a cleaner looking transition to the head tube, which appears to be a 44mm head tube. The new fork does not have that and its not necessary, but it is not a visually pleasing transition. That is just the way it works when you install a straight steerer steel fork in a 44mm head tube. As long as you have properly pressed on the crown race to your new fork and it sits flush with the crown race seat, there is no problem.