Once you've created your new material in one part file, you can export it to a user material XML file (just make sure that you place it somewhere other than the default directory since users are not allowed to create new material files in the NX material folder). Just go to...
Tools -> Materials -> Manage Library Materials...
...and set the Source Material List to 'Local Materials' and select the material(s) desired to be exported, enter a name for you user defined material file in the Target Material Library field (remembering to place to in some safe but accessible location) and hit OK.
Now when you open a new part and you wish to use your new material, just go to Assign Material dialog, expand the 'Libraries' section under Material List and toggle on 'User MatML Library' and select the folder where you've stored your material XML file(s). Or to make this even more 'automatic' go to...
Customer Defaults -> Gateway -> Materials-> Location(s)
...and toggle on the 'Enable' option in the 'Site MatML Library' section. Now in the 'MatML File Name' option, browse to your safe folder with your materials and select one of them (it's not important which one). And then include just the path under the 'Directory Name' option.
Now when you go to Assign Material this folder will be referencd by default and you can select your custom material. And if no matter where you create any future new materials and you include them in that safe folder, they will automatically be made available whenever you assign material in any part file. Note that when you are assigning materials, the custom materials will only show up if you've toggled OFF the 'NX Material Library' option in the 'Libraries' section of the Assign Material dialog.
Anyway, give that a try and see if this provides you what you're looking for.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.