rammy17,
In a Part file, use the native SW Weldment tool. It will create a multi-body part. In the cutlist, you can independently define any material you want for each of the Items in the Cutlist. "Merged bodies" have to be one material (because they will appear as one Item in the Cutlist), so make sure to to Uncheck "Merge Result" when defining the feature.
Note, if you are Patterning or Mirroring, you must use the Feature Scope correctly when initially creating this feature. Make sure you choose correctly as far as if you are trying to Pattern/Mirror a Feature or a Body, because you can not later edit the Pattern/Mirror Feature and choose the other. You must delete the feature to change the scope from Feature-to-Body or vice-versa.
This really is the best way to make a Weldment, and SW really excels with this tool. Just make sure each "body" is an item that in the real word would have to welded to another "body". Periodically check your "Bodies" folder to make sure you're getting the separate bodies that you want.
Do not model components to their Machined size. The top portion of your Feature Tree should be the bodies in their "As Welded" state, and then add your Machined Features. Make sure to set up the "As Welded" and "As Machined" configurations to match your intent. If you don't, you may not be able to link the required dimensions for the Stock Material sizes, plus it could require a little more manual tweaking to get your Cutlist Quantities correct.
While in the "As Welded" configuration, assign properties to each Cutlist Item; like Material, Shape, parametrically link to dimension values, or whatever other property you want.
Once you're in the 2D Drawing, all you have to do is "Insert" a Cutlist Table based off of one of the views of your weldment in the "As Welded" configuration.
I hope this wasn't information overload. I can clarify more if needed.
Ken