A Grain Subdivision Study on a Cyclic Deformed Nickel-Based Superalloy Using Synchrotron X-Ray Micro-Beam Diffraction E-Wen Huang 1, * , Rozaliya Barabash 2, 3 , Gene E. Ice 2 , Peter K. Liaw 1 , Hahn Choo 1 , Lee M. Pike 4 , and Dwaine L. Klarstrom 4 1. Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996, USA 2. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA 3. Center for Materials Processing, University of Tennessee, Knoxville, TN 37996, USA 4. Department of Technology Engineering, Haynes International Inc., Kokomo, IN 46904, USA Statement of Purpose Nickel–based superalloy is a practical important structural material used as a corrosion resistant component. A major issue for using superalloys, which to manufacture a specific design of pipe-lines or tanks for chemistry, is the understanding of its fatigue life and its associated behavior. The fatigue endurance must ensure that the superalloys serve the duties for their expected life. To address this purpose, the knowledge of the fatigue fracture mechanics has to be developed. The current study focuses on the atomic structures which are responsible for fatigue fracture by using micro-beam technology at the synchrotron X-ray source. The penetration of the high energy X-ray can reach about 50 micrometer. As a result the atomic structures of the cyclic deformed superalloy can be studied as a function of the distance within one grain and from adjacent grains. Experimental procedure The testing nickel-based superalloy is HASTELLOY ® C-22HS TM alloy (Ni-21Cr-17Mo in the weight percentage). The alloy is designed to be used at corrosive conditions. The alloy is mill annealed at 1,080 o C to minimize the formation of precipitates and to achieve