RATE THEORY INVESTIGATION OF INFLUENCE OF CASCADE CLUSTER FORMATION AND SOLUTE TRAPPING ON POINT-DEFECT AGGLOMERATION AND EXTENDED DEFECT EVOLUTION

Using a composite model of point defect behavior and microstructural e volution, the influence of cascade vacancy cluster formation and vacan cy trapping at solute atoms on the point defect fluxes, point defect c lustering and extended defect development was investigated. The point defect model calculates the concentrations of isolated and trapped poi nt defects, and of simple or complex clusters. The extended defect mod el consists of individual rate theory models describing the evolution of cavities, Frank loops and network dislocations. Cascade vacancy clu sters were observed to become the dominant sink for point defects in t he early stages of irradiation at low to intermediate temperature. The refore, the sink strength of the vacancy clusters largely determines t he point defect flux and agglomeration rates. The calculations also sh owed that solute traps affect the irradiated microstructure to a large extent for certain combinations of trap concentration and trapping en ergy. Both the trap concentration and trapping energy have a non-monot onic effect on vacancy clustering though they do not change the inters titial flux significantly.