Microstructural characterisation of 160 MeV oxygen irradiated niobium

ABSTRACT

Microstructural changes due to 160 MeV oxygen ion irradiation on pure Nb have been characterised using X-ray Diffraction Line Profile Analyses. Microstructural parameters such as coherent domain size, microstrain within the domain and dislocation density are evaluated from the homogeneously damaged region. It is observed that the domain size decreases along with an increase in microstrain and dislocation density as a function of dose. The local changes in the microstructure have also been evaluated in terms of band contrast, mean angular deviation and local misorientation from electron backscattered diffraction data at the surface and an intermediate depth in the homogenously damaged region of selected irradiated samples and in the unirradiated sample. An increase in mean angular deviation and local misorientation is observed in the highest dose sample, which may be an indication of dislocation loop formation. Defect clusters and dislocation loops are observed using transmission electron microscopy in the highest dose sample. Microhardness measurement has also been carried out on the unirradiated and irradiated samples to correlate the microstructural changes with the mechanical property as a function of dose. It is observed that the hardness of the material increases as a function of dose due to the formation of defect clusters and dislocation loops that pin the movement of dislocations. Finally, a comparison of the microstructures in proton and heavy ion irradiated samples at approximately similar dpa-rate has been carried out to understand the effect of the ion species on the defect morphology.

KEYWORDS:

• Microstructure
• oxygen irradiation
• X-ray diffraction
• EBSD
• niobium

Disclosure statement

No potential conflict of interest was reported by the author(s).