The role of frictional stress on the generation of misfit dislocations

The concept of misfit strain driving dislocations to an interface between two different phases leads to a residual strain that is not accommodated by the misfit dislocations. The residual strain occurs when the misfit stress is reduced to a value insufficient to generate further misfit-accommodating dislocations at the interface. This idea has been applied to epitaxial films to account for the relaxation of strain with increasing film thickness. It is here extended to the case of endotaxial interfaces between a solid matrix and precipitate. This paper builds upon work of Nabarro published in 1940 and the frictional stress to be overcome to move dislocations into the interface

Microstructure of triple-beam ion irradiated Fe and Fe-Cr alloys

The development of defect structures in Fe-10% Cr, triple-beam (He/sup +/, D/sub 2//sup +/ and 4 MeV Fe/sup + +/) ion irradiated to 10 dpa at temperatures from 725 to 950 K has been studied. Limited cavity formation was observed. Peak swelling of approx. 0.02% occurred at irradiation temperatures of approx. 850 K. Similar irradiations at this temperature led to approx. 0.22% swelling in iron, while no cavities were observed in Fe-5% Cr. Calculations have shown that cavities formed at 875 K and above are more bubble-like than those at lower temperatures. Dislocation structures varied from interstitial dislocation loops with b = a at low temperatures to a coarse dislocation network at 850 K. Large dislocation loops had a convoluted shape which suggested that loop growth had occurred preferentially in directions. The results are discussed and related to current swelling suppression mechanisms for ferritic steels