The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggesstions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA, 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any oenalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. a. REPORT Elevated-temperature deformation mechanisms in Ta2C: An experimental study 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: A polycrystalline a-Ta2C bar, fabricated by hot isostatic pressing, was tested in four-point bending at approximately 1930 C. The sample showed significant plastic deformation. Transmission electron microscopy, using two-beam defect analysis, confirmed pyramidal dislocation slip of the type a=3h1123if1011g. Basal and prismatic slip of a=3h1120i type could not be determined because of significant contrast interference from stacking faults that formed in the material. The increase in stacking fault density observed after thermomechanical 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES The views, opinions and/or findings contained in this report are those of the author(s) and should not contrued as an official Department of the Army position, policy or decision, unless so designated by other documentation. 12. DISTRIBUTION AVAILIBILITY STATEMENT Approved for public release; distribution is unlimited. UU 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 6. AUTHORS 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS UHTC; Slip system; Dislocations; TEM; Plastic deformation Billie Wang, Christopher R. Weinberger, Lawrence E. Matson, Gregory B. Thompson, Nicholas De Leon University of Alabama - Tuscaloosa Sponsored Programs The University of Alabama Tuscaloosa, AL 35487 -0104 REPORT DOCUMENTATION PAGE b. ABSTRACT UU c. THIS PAGE UU 2. REPORT TYPE New Reprint 17. LIMITATION OF ABSTRACT UU 15. NUMBER OF PAGES 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 5c. PROGRAM ELEMENT NUMBER 5b. GRANT NUMBER 5a. CONTRACT NUMBER W911NF-08-1-0300 611102 Form Approved OMB NO. 0704-0188 54397-MS.9 11. SPONSOR/MONITOR'S REPORT NUMBER(S) 10. SPONSOR/MONITOR'S ACRONYM(S) ARO 8. PERFORMING ORGANIZATION REPORT NUMBER 19a. NAME OF RESPONSIBLE PERSON 19b. TELEPHONE NUMBER Gregory Thompson 205-348-1589 3. DATES COVERED (From - To) Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 -