The effect of W/Cu phase boundary on the evolution of end-of-range dislocation loop induced by He ion irradiation at 773 K

Abstract

Dislocation loops, a type of irradiation defect, significantly degrade the mechanical properties of nuclear materials. However, the presence of interfaces can effectively mitigate the accumulation of such defects. In this study, the influence of the W/Cu phase boundary (PB) on the evolution of end-of-range (EOR) dislocation loops was investigated using He ion irradiation at 773 K. A simplified approach utilizing Transmission Electron Microscopy (TEM) characterization of EOR dislocations was proposed to analyze the complex defect behavior. Statistical analysis of EOR dislocation loops revealed that the W/Cu phase interface significantly influences the distribution of dislocation loops. On the W side, a low dislocation density region was observed near the phase boundary, where the proportion of b = 1/2 〈111〉 type dislocations was significantly reduced. On the Cu side, the dislocation loop density near the phase boundary was higher than in regions farther from the interface. Additionally, a similar but slightly lower dislocation density region was observed near the phase boundary. This phenomenon can be attributed to two primary mechanisms: the high sink strength of the phase boundary and the elastodynamic image forces exerted by the interface. The former mechanism dominates defect evolution in W, while both mechanisms collectively influence defect behavior on the Cu side. Observations of irradiation defect evolution near W/Cu PB will enhance the fundamental understanding of damage processes in tungsten‑copper divertors for fusion reactors.