Extended Defects

Figure 6.10 illustrates schematically all the point defect and other higher order defects that may occur. Besides stable faulted Frank loops, SIAs may form meta­stable arrangement of SIAs that do not reorganize into a stable, glissile form by the end of thermal spike. They are important because they do not migrate away from the cascade and act as precursors to extended defects. Mobile clusters can interact with other clusters or with impurity atoms. Vacancy clusters that form perfect dislo­cation loops are also intrinsically glissile. Formation of dislocation loops and voids occurs from defect clusters. Interstitial-type dislocation loops in deuterium — irradiated molybdenum and tungsten are shown in Figure 6.11.

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Figure 6.10 Schematics of various radiation-induced defects in crystals. Courtesy: Professor Helmut Foll, University of Kiel, Germany.