Effect of pre-existing dislocations and precipitates on microstructure evolution in W-0.5ZrC alloy during in-situ He+ & H2+ dual-beam synergistic irradiation

Abstract

Bubble evolution in different defect sinks has a crucial effect on the properties of materials for fusion reactor. Here, transmission electron microscopy (TEM) was used to in-situ investigate bubble evolution in different defect sinks, including pre-existing dislocations and precipitates in W-0.5ZrC alloy during He+ & H2+ dual-beam synergistic irradiation at 900 °C. The average size and volume number density of bubbles with increasing irradiation dose were obtained, revealing not only the significant effect of different types of defect sinks, but also the obvious impact of the same type of defect sinks in different states. It was found that linear pre-existing dislocations promoted bubble growth while inhibited nucleation. Pre-existing dislocations characterized by curved form exhibited strong inhibition effect on bubble nucleation, while pre-existing dislocations with staggered-mesh form, not only inhibited bubble growth but also suppressed nucleation compare to the linear pre-existing dislocations. ZrC precipitates had minimal effect on bubble growth, but could decrease the bubble nucleation. Dispersed small precipitates could better reduce the bubble nucleation sites in the early stage of irradiation. Once the absorption capacity of small precipitate was saturated, bubble growth might accelerate sharply. The presence of hydrogen made the linear pre-existing dislocation maintain high mobility. The current research results are of great significance for understanding the irradiation behavior of tungsten alloys and optimizing the preparation process.