[SY-C7] Symposium C-7

[SY-C7] Molecular dynamics simulations of dislocation avalanche emissions in FCC and BCC crystals

^○Javier Varillas^1,2, Jan Očenášek², Jorge Alcalá¹ (1.New Technologies Research Centre, University of West Bohemia in Pilsen, Czech Republic, 2.Department of Materials Science and Metallurgical Engineering, InSup, ETSEIB. Universitat Politècnica de Catalunya, Spain)

Plastic deformation in crystalline materials is characterized by intermittent collective dislocation glide processes, or dislocation avalanches [1, 2, 3]. Here we perform a comprehensive set of molecular dynamics (MD) simulations to investigate the influence of strain-rate effects upon the emission of dislocation avalanches in body-centered cubic (BCC) and face-centered cubic (FCC) microcrystals. The MD simulations comprise periodic (representative) cells containing dense dislocation arrangements injected prior to the application of uniaxial displacement. Our results enable assessment of the transition from a continuous deformation mode, developed under a large strain-rate, to the characteristic serrated discontinuous mode (indicating dislocation-mediated crystal plasticity) under a lower strain rate. In the latter, the stress-strain curves can be essentially probed under strict displacement control, enabling direct comparison with the avalanche-size distributions from quasi-static micropillar compression experiments [3]. Moreover, our findings shed new light on the role of strain hardening and dislocation cross-slip in FCCs as well as on the thermally-activated glide of screw dislocations in BCCs upon the avalanche distributions, including avalanche truncation at large plastic slip events [3].


[1] M. C. Miguel, A. Vespignani, S. Zapperi, J. Weiss and J.-R. Grasso, "Intermittent dislocation flow in viscoplastic deformation", Nature, vol. 410, 2001.
[2] R. Maaβ, M. Wraith, J. T. Uhl, J. R. Greer and K. A. Dahmen, "Slip statistics of dislocation avalanches under different loading modes", Phys. Rev. E, vol. 91, no. 4, 2015.
[3] J. Alcala, J. Ocenasek, K. Nowag, D. Esqué-de-los-Ojos, R. Ghisleni and J. Michler, "Strain hardening and dislocation avalanches in micrometer-sized dimensions", Acta Materialia , vol. 91, 2015.