Scale-dependent pop-ins in nanoindentation and scale-free plastic fluctuations in microcompression

Nanoindentation and microcrystal deformation are two methods that allow probing size effects in crystal plasticity. In many cases of microcrystal deformation, scale-free and potentially universal intermittency of event sizes during plastic flow has been revealed, whereas nanoindentation has been mai...

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Bibliographic Details
Published in:Journal of materials research 2020, Vol.35 (2), p.196-205
Main Authors: Shimanek, John, Rizzardi, Quentin, Sparks, Gregory, Derlet, Peter M., Maaß, Robert
Format: Article
Language:English
Subjects:
Applied and Technical Physics
Biomaterials
Deformation effects
Extreme values
Inorganic Chemistry
Intermittency
Materials Engineering
Materials research
Materials Science
Microcrystals
Nanoindentation
Nanomechanics and Testing
Nanotechnology
Plastic flow
Plastic instability
Size effects
Statistical tests
Stress state
Variation
Weibull distribution
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Summary:Nanoindentation and microcrystal deformation are two methods that allow probing size effects in crystal plasticity. In many cases of microcrystal deformation, scale-free and potentially universal intermittency of event sizes during plastic flow has been revealed, whereas nanoindentation has been mainly used to assess the stress statistics of the first pop-in. Here, we show that both methods of deformation exhibit fundamentally different event-size statistics obtained from plastic instabilities. Nanoindentation results in scale-dependent intermittent microplasticity best described by Weibull statistics (stress and magnitude of the first pop-in) and lognormal statistics (magnitude of higher-order pop-ins). In contrast, finite-volume microcrystal deformation of the same material exhibits microplastic event-size intermittency of truncated power-law type even when the same plastic volume as in nanoindentation is probed. Furthermore, we successfully test a previously proposed extreme-value statistics model that relates the average first critical stress to the shape and scale parameter of the underlying Weibull distribution.
ISSN:0884-2914
2044-5326
DOI:10.1557/jmr.2019.386