Not really; I challenge you to find a dictionary that says the two terms are synonymous.

Originally an axiom was a proposition that was "self-evident". But there's a long history of people questioning "self-evident" propositions, happily for us.

There seems to be a colloquial usage of "axiom" to mean a proposition that someone doesn't want us to question. I deprecate that usage. For example, the Law of The Excluded Middle is an axiom, but it has often been questioned; ergo, it is not unquestionable.