On the formation mechanisms of intragranular shear bands in olivine by stress-induced amorphization
(2022) Acta Materialia — Vol. 239, p. 118247 (2022)
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- Authors
Cordier, Patrick 
- Abstract
- Intragranular amorphization shear lamellae are found in deformed olivine aggregates. The detailed trans- mission electron microscopy analysis of intragranular lamella arrested in the core of a grain provides novel information on the amorphization mechanism. The deformation field is complex and heteroge- neous, corresponding to a shear crack type instability involving mode I, II and III loading components. The formation and propagation of the amorphous lamella is accompanied by the formation of crystal defects ahead of the tip. These defects are geometrically necessary [001] dislocations, characteristics of high-stress deformation in olivine, and rotational nanodomains which are tentatively interpreted as disclinations. We show that these defects play an important role in dictating the path followed by the amorphous lamella. Stress-induced amorphization in olivine would thus result from a direct crystal-to- amorphous transformation associated with a shear instability and not from a mechanical destabilization due to the accumulation of high number of defects from an intense preliminary deformation. The pref- erential alignment of some lamellae along (010) is a proof of the lower ultimate mechanical strength of these planes.
- Affiliations
University of Antwerp Electron Microscopy for Materials Science Universität Bayreuth Bayerisches Geoinstitut Universitéde Montpellier and CNRS Géosciences Montpellier Univ. Lille UMET - UnitéMatériaux et Transformations Institut Universitaire de France
Citations
Idrissi, H., Béché, A., Gauquelin, N., Ul-Haq, I., Bollinger, C., Demouchy, S., Verbeeck, J., Pardoen, T., Schryvers, D., & Cordier, P. (2022). On the formation mechanisms of intragranular shear bands in olivine by stress-induced amorphization. Acta Materialia, 239, 118247. https://doi.org/10.1016/j.actamat.2022.118247 (Original work published 2022)