Crystal Structure of Elongated Thin Foils of Fe and V

Abstract

Kiritani et al. have recently reported that a large number of vacancy clusters are formed in plastically elongated thin foil of fcc metals and that no dislocations at all are observed in the thin portion of the elongated film. These findings suggest that elongation proceeds by atom transportation accompanied by generation of vacancies. In the present work, strips of prototype bcc metals of iron and vanadium were elongated to fracture, and thin portions that can be observed under TEM; i.e. , fractured edges, were observed by electron microscopy. The results show that iron thin foils that had been elongated in pure helium gas reacted with residual oxygen atoms such that the thin portions transformed to α-Fe 2 O 3 . Iron thin foil that had been elongated under a 10 −6 Pa vacuum showed usual bcc structure, and void-like defects were observed. Strips of vanadium were elongated to fracture at 77 K and 293 K, and large number of void-like defects were observed in as-elongated specimens. In thin vanadium foil that had been elongated at 673 K, TEM visible defects were not observed initially, and void like defects appeared after 200 keV electron illumination for 60 minutes. Stereo-microscopic examination showed that void-like defects had formed inside vanadium thin foil.