Should I ask permission of my co-authors when republishing an article? In the university that I am working, which is more technically than research oriented, they want me to publish one of my past articles in a faculty magazine that they are planning to print. I have chosen one from the IEEE, and I have read that they have that possibility. I would like to know if I should mention that to my other co-authors or is it not necessary?

Thanks for your help
Yes.

As a courtesy, one should always inform co-authors of such things. One doesn't necessarily expect replies (since no action is required...), but one is taking action on "property" that is partially "owned" by other people, so some notification, or even request for permission (which would presumably be unhesitatingly granted), is entirely reasonable.