The effects of temperature and strain rate in fcc and bcc metals during extreme deformation rates

M Yaghoobi and GZ Voyiadjis, ACTA MATERIALIA, 151, 1-10 (2018).

DOI: 10.1016/j.actamat.2018.03.029

The present work investigates the effects of temperature and strain rate in fcc and bcc metallic samples subjected to the extreme strain rates, higher than 10(8)s(-1), using large scale atomistic simulation. In addition to the stress-strain curve, the microstructural information of the samples is studied to capture the underlying mechanisms of temperature and rate effects. The results show that as the strain rate increases, the material strength increases in a way that the underlying mechanisms of strength depend on the material crystal structure. However, the results show that the material response dependency on temperature is much smaller than that of the strain rate in the region of extreme deformation rates. In other words, the change in temperature does not lead to a noticeable change in the material response. In the case of fcc metals subjected to the extreme strain rates, the results show that the work hardening mechanism, i.e., interaction of dislocation with one another, is the governing mechanism of material strength, and the contribution of thermal activation mechanism is negligible. In the case of bcc metals subjected during the extreme rate deformations, both work hardening and phonon drag mechanisms are important, while the former one is dominant. Again, the thermal activation mechanisms can be neglected in the regime of high strain rates. Finally, a multi-scale model is incorporated to capture the observed response of material in the regime of extreme strain rates. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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