Acoustic Emission from Porous Collapse and Moving Dislocations in Granular Mg-Ho Alloys under Compression and Tension

Chen, Yan and Ding, Xiangdong and Fang, Daqing and Sun, Jun and Salje, Ekhard K. H. (2019) Acoustic Emission from Porous Collapse and Moving Dislocations in Granular Mg-Ho Alloys under Compression and Tension. Scientific Reports, 9 (1). ISSN 2045-2322 DOI https://doi.org/10.1038/s41598-018-37604-5

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Official URL: https://doi.org/10.1038/s41598-018-37604-5

Abstract

We identified heterogeneous Mg-Ho alloys as an ideal material to measure the most extensive acoustic emission spectra available. Mg-Ho alloys are porous and show a high density of dislocations, which slide under external tension and compression. These dislocations nucleate near numerous heterogeneities. Two mechanisms compete under external forcing in the structural collapse, namely collapsing holes and the movements of dislocations. Their respective fingerprints in acoustic emission (AE) measurements are very different and relate to their individual signal strengths. Porous collapse generates very strong AE signals while dislocation movements create more but weaker AE signals. This allows the separation of the two processes even though they almost always coincide temporarily. The porous collapse follows approximately mean-field behavior (ε = 1.4, τ’ = 1.82, α = 2.56, x = 1.93, χ = 1.95) with mean field scaling fulfilled. The exponents for dislocation movement are greater (ε = 1.92, τ’ = 2.44, α = 3.0, x = 1.7, χ = 1.42) and follows approximately the force integrated mean-field predictions. The Omori scaling is similar for both mechanisms. The Bath’s law is well fulfilled for the porous collapse but not for the dislocation movements. We suggest that such ‘complex’ mixing behavior is dominant in many other complex materials such as (multi-) ferroics, entropic alloys and porous ferroelastics, and, potentially, homogeneous materials with the simultaneous appearance of different collapse mechanisms.

Item Type: Article
Uncontrolled Keywords: 2018AREP; IA74
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
07 - Gold Open Access
Journal or Publication Title: Scientific Reports
Volume: 9
Identification Number: https://doi.org/10.1038/s41598-018-37604-5
Depositing User: Sarah Humbert
Date Deposited: 13 Mar 2019 11:37
Last Modified: 13 Mar 2019 11:37
URI: http://eprints.esc.cam.ac.uk/id/eprint/4432

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