On the Shimano website they don't seem to use the term "hardened" with respect to the rings.
The XT comes with all aluminum rings.
The LX comes with aluminum rings on the outer and middle, and a steel inner ring.
Something else to think about before you go down that path. The chainline for those cranksets, LX and XT is 50 mm. It's meant to go with a 135 mm spaced hub. If you go with those cranksets you may be inviting more surgery than you intended.
Any reason why you don't just swap chainrings for the ones you want?
Speedo