A molecular dynamics study of the role of grain size and orientation on compression of nanocrystalline Cu during shock
MM Sichani and DE Spearot, COMPUTATIONAL MATERIALS SCIENCE, 108, 226-232 (2015).
The molecular dynamics method is used to investigate the dependence of grain size and grain orientation on deformation in nanocrystalline Cu during shock. Particle velocities from 1.0 to 3.4 km/s are applied to nanocrystalline Cu samples with grain sizes from 6 to 26 nm. Results show that grain size does not significantly influence the temperature and pressure of the Hugoniot state. However, grain size, grain orientation, and particle velocity do influence the details by which Cu is uniaxially compressed into a BCC structure at pressures between 100 and 200 GPa behind the shock front. The computed atomic percentage of BCC structure ranges between 3.4% and 9.2% depending on grain diameter at a particle velocity of 1.5 km/s, reaches a maximum between 23.3% and 30.7% at a particle velocity of 2.4 km/s, and then decreases to approximately 0.0% at a particle velocity of 3.2 km/s. At a particle velocity of 2.4 km/s, the atomic percentage of BCC structure observed during shock increases with increasing grain size, while this trend is reversed at a particle velocity of 1.5 km/s. Moreover, the observation of BCC structure strongly depends on grain orientation; grains with < 100 > directions closely aligned with the shock loading direction show a higher percentage of BCC structure, implying a tetragonal transformation path (Bain path). (C) 2015 Elsevier B.V. All rights reserved.
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