Scale-dependent pop-ins in nanoindentation and scale-free plastic fluctuations in microcompression. Issue 2 (28th January 2020)

• Record Type: Journal Article
• Authors: Shimanek, John; Rizzardi, Quentin; Sparks, Gregory; Derlet, Peter M.; Maaß, Robert
• Is Part Of: Journal of materials research. Volume 35:Issue 2(2020)
• Page Start: 196
• Page End: 205
• Publication Date: 2020-01-28
• Subjects: nanoindentation, -- microstructure, -- crystal; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1557/jmr.2019.386
• Languages: English
• ISSNs: 0884-2914

Abstract

Abstract: Abstract : 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.