I am struggling to find an answer to that simple question. I realized I can't find the option in Inventor Fusion 2013 which would allow to create 1 solid body out of 2 without any splits, fringes, nothing that will show that previously it's been 2 separate bodies. Maybe screenshots would be helpful. Please help me to sort this out. Thank you.
If these are separate components you can use the boolean command.
In order for different materials to be applied on one body or component there should be an edge of some kind. So any face will take a new material, right up to it's boundary edges.
If you need to create edges, use the Split Face command. First sketch a line as a cutting tool, then use Split Face to cut the face where the line is. Material can be applied differently on either side of the split.