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The influence of ion irradiation on structural rejuvenation and relaxation in a Zr-based metallic glass (MG) is investiagted. The MG can be structurally rejuvenated with increasing irradiation dosage from 0 to 3 dpa, which reflects in increased activation volumes of shear-transformation zones. However, structural relaxation dominates at a high irradiation dosage (4 dpa) resulting in higher hardness. The anelastic-relaxation processes in the irradiated MG can be understood in terms of the coordination mechanism of the deformation modes associated with free volume. Ion irradiation appears to be a promising and effective way to modify MGs and to, thus, manipulate plastic flow. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A radiation-induced order–disorder transformation occurs in many A2B2O7 pyrochlore structure-types by disordering of the A- and B-site cations, as well as anion vacancies. The ionic conductivity increases up to two orders of magnitude due to this order–disorder transformation. This irradiation-induced order–disorder transition has been examined in detail using ion beam irradiations and in situ transmission electron microscopy. Under ion irradiation, the ordered pyrochlore superstructure transforms to an anion-disordered pyrochlore prior to a final transformation to a cation-disordered defect-fluorite structure-type. The anion-disordered pyrochlore structure displays a partial ordering of the A- and B-site cations and complete disordering on the anion array—as evidenced by the disappearance of characteristic diffraction maxima resulting from ordering of the oxygen sublattice. These results suggest that anion disorder precedes cation disordering in the pyrochlore structure. [Copyright &y& Elsevier]