Rheology of amorphous olivine thin films characterized by nanoindentation

The rheological properties of amorphous olivine thin films deposited by pulsed laser deposition have been studied based on ambient temperature nanoindentation under constant strain-rate as well as re-laxation conditions. The amorphous olivine films exhibit a viscoelastic-viscoplastic behavior with a significant rate dependency. The strain-rate sensitivity m is equal to similar to 0 . 05 which is very high for silicates, indicating a complex out-of-equilibrium structure. The minimum apparent activation volume determined from nanoindentation experiments corresponds to Mg and Fe atomic metallic sites in the (Mg,Fe)(2)SiO4 crystalline lattice. The ambient temperature creep behavior of the amorphous olivine films differs very much from the one of single crystal olivine. This behavior directly connects to the recent demonstration of the activation of grain boundary sliding in polycrystalline olivine following grain boundary amorphization under high-stress. (C) 2021 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc.

Automated summary

The study reveals that amorphous olivine thin films deposited by pulsed laser deposition exhibit viscoelastic-viscoplastic behavior with significant rate dependency, suggesting a complex out-of-equilibrium structure. The ambient temperature creep behavior of the amorphous olivine films differs significantly from single crystal olivine, which is related to the activation of grain boundary sliding in polycrystalline olivine following grain boundary amorphization under high-stress conditions.