FIELD ION MICROSCOPY OF FILAMENTARY IRON CRYSTALS.
Final rept. Jul 64-May 65,
PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF PHYSICS
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Filamentary iron crystals of the C, D and H Series as furnished by Air Force Materials Laboratory were observed in several cross sections along the total length using the field ion microscope. No change in crystal orientation was noticed for 001, 111 and 110 oriented specimens. The previously discussed amorphous core structure was found to be caused by yield in the 111 region due to the field stress. Hydrogen promoted field evaporation is a means of shaping the tip surface at a reduced field strength so that artifacts can be avoided and perfect 111 planes can be developed. The few dislocations observed place no limit on the strength of the tip core which withstands a field stress of 710 kgsq mm, or 4 of the bulk modulus. Author