Kant and Aristotle both view duty as something that comes, not just from what is lawful or what is expected, but from the inside. Morality has nothing to do with what is expected, but from the character-the inner strength and disposition. However, that is where the similarities end. This paper discusses the differences between Kant and Aristotle in their views of morality, duty and choices.
From the Paper:
"According to Kant, duty leaves little room for choices. Freedom means actually having a choice, but duty is what you need to do. Duty is reasons-choice is freedom, and when you can choose what to do, morality and ethics take a back seat. What is considered moral to some people may not be empowering to all people, and when someone says, "This is moral-this is what you have a duty to do. Therefore it is the law", not everyone may agree and will become disempowered when they are required to do the duty. Morality is nothing more than self-delusion and exaggerated conceit. (Timmermann, 10) What one person considers "saintly", may just be "normal" to someone else, and therefore not a moral or ethical duty."