  Amorphous interfacial complexions are particularly resistant to radiation
damage and have been primarily studied in alloys with good glass-forming
ability, yet recent reports suggest that these features can form even in
immiscible alloys such as Cu-Ta under irradiation. In this study, the
mechanisms of damage production and annihilation due to primary knock-on atom
collisions are investigated for amorphous interphase and grain boundaries in a
Cu-Ta alloy using atomistic simulations. Amorphous complexions, in particular
amorphous interphase complexions that separate Cu and Ta grains, result in less
residual defect damage than their ordered counterparts. Stemming from the
nanophase chemical separation in this alloy, the amorphous complexions exhibit
a highly heterogeneous distribution of atomic excess volume, as compared to a
good glass former like Cu-Zr. Complexion thickness, a tunable structural
descriptor, plays a vital role in damage resistance. Thicker interfacial films
are more damage-tolerant because they alter the defect production rate due to
differences in intrinsic displacement threshold energies during the collision
cascade. Overall, the findings of this work highlight the importance of
interfacial engineering in enhancing the properties of materials operating in
radiation-prone environments and the promise of amorphous complexions as
particularly radiation damage-tolerant microstructural features.
