When do replicated chromosomes are aligned in the center

During Metaphase

Explanation:

During Metaphase the cell chromosome align themselves in the middle of the cell.This occur due to a cellular process called "Tug of War".

The chromosome which have been replicated and joined at the central point  called centromere are called sister chromatids

Prior to metaphase , Kinetochore type of protein are formed around the centromere. Long protein filament called kinetochore are extended from poles to other end of the cell attached to kinetochore.

Therse is important checkpoint in the middle of mitosis called metaphase.

At this point cell ensure that , it is ready to divide or not.

Once the cell ensure that everything is ready to divide. Only after then , yhe cell enters the fourth phase called anaphase.