Most times it is the BRUSHES inside which are what make contact with the STATOR that get worn and need replaced.
Taking into account my previously described lack of knowledge of automotive technology, I don't think alternators (AC output) have brushes. A generator (DC output), like in my '65 VW, has brushes, but I think that is why they went to alternators.
An alternator will have diodes, used to feed the DC circuit in the car. These are the common failure point in an alternator and, are also, easy to replace.
I may be wrong and would ask the capn to give the definitave answer.
nacl