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AbstractThis work highlights the effect of proton irradiation in the presence of preexisting defects in the Nb-1Zr-0.1C alloy. To introduce the initial defects, the Nb-1Zr-0.1C alloy was subjected to cold rolling (10% and 20%) prior to irradiation. Characterization of the irradiated material was performed using detailed X-ray diffraction line profile analyses. The results, in terms of various microstructural parameters, revealed that the preexisting defects in these materials act as effective sinks for irradiation-induced defects during the initial irradiation.Electron backscattered diffraction analyses suggested that the fraction of low-angle grain boundaries plays a crucial role during irradiation and determines the outcome of the competing process between defect annihilation and defect production. Transmission electron microscopy analyses revealed that the black dots were coexisting with carbide precipitate in the cold-rolled Nb alloy after irradiation.Mechanical properties were also assessed by measuring microhardness to correlate with the changes in microstructure after irradiation. The change in yield strength calculated from the change in the microhardness value as a function of dose indicated that the 20% cold-rolled Nb alloy was more radiation resistant than the 10% cold-rolled Nb alloy at ambient temperature and a low-dose regime. To see the effect of alloying elements, similar studies were also carried out on pure Nb, and the results were compared with that of the Nb-1Zr-0.1C alloy. All these findings help to develop a better understanding of the behavior of the proton-irradiated Nb-1Zr-0.1C alloy in the presence of preexisting defects introduced by means of cold rolling prior to irradiation. [ABSTRACT FROM AUTHOR]

One of the proposed materials for structural application in compact high-temperature reactors (CHTRs) is Nb-1Zr-0.1C alloy. Using the Variable Energy Cyclotron at the Variable Energy Cyclotron Centre, Kolkata, Nb-1Zr-0.1C alloy was irradiated with a 160-MeV oxygen (O6+) ion up to three different doses. Emulation of neutron irradiation by ion irradiation could be achieved as the weighted recoil spectra of the oxygen ion are found to be similar to the neutron recoil spectra of CHTRs within recoil energy ranging from 100 eV to 100 keV. The irradiated materials along with one as-received sample were characterized using different X-ray diffraction line profile analyses (XRDLPAs) to systematically evaluate microstructural parameters. A decrease in the domain size with an increase in microstrain and dislocation density is observed at first dose and then found to saturate with further irradiation. An increase in the Wilkens arrangement parameter indicates the formation of less correlated dislocations (clusters) after irradiation. Transmission electron microscopy analysis of as-received and highest-dose samples shows the formation of densely populated defect clusters after irradiation. Nanohardness increased after irradiation due to pinning of the dislocation movement by point defects and defect clusters/loops, as well as carbides in the matrix. The results extracted from the XRDLPAs are compared with our earlier studies of light ion–irradiated (H+) Nb-1Zr-0.1C alloy and oxygen-irradiated pure Nb to understand the effect of the type of ion and the alloying elements, respectively, on the evolution of the microstructure. It may be concluded that changes in dose and dose rate affect the movement of point defects toward sinks. Hence, possible correlated dislocation formation is observed in light ion–irradiated Nb alloy, but correlation is found to decrease with dose for heavy ion–irradiated Nb alloy. On the other hand, the presence of finely dispersed carbides restricts the formation of dislocation loops by making complexes with the defects in heavy ion (O6+)–irradiated Nb-1Zr-0.1C alloy, which is in contrast to pure Nb irradiated using the heavy ion (O6+) in a similar environment. [ABSTRACT FROM AUTHOR]