Mechanism of nanocrystallization temperature shifting during ion irradiation of metallic glasses

L Shao and D Chen and A Zare and DA Lucca, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 497, 28-33 (2021).

DOI: 10.1016/j.nimb.2021.03.012

Nanocrystallization temperature changes of metallic glasses upon ion bombardment were investigated. For Zr50Cu35Al7Pd5Nb3 metallic glass membranes irradiated by 1 MeV Kr ions, in situ transmission electron microscopy characterization show that nanocrystallization temperatures decrease with increasing ion fluences. The higher the ion fluence, the lower the temperature at which nanocrystals start to form. Using Monte Carlo ion transport simulations and molecular dynamics simulations, we show that upon ion bombardment, spatial distributions of positive free volume are slightly shallower than that of negative free volume. Following local recombination of the free volume of opposite signs, positive (excessive) free volume is introduced in the near surface region, and glass transition temperatures and crystallization temperatures decrease as a function of excessive free volumes.

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