Atomistic simulation of tension-compression asymmetry and its mechanism in titanium single-crystal nanopillars oriented along the 1 1 (2)over- bar 0 direction

JQ Ren and QY Sun and L Xiao and J Sun, COMPUTATIONAL MATERIALS SCIENCE, 147, 272-281 (2018).

DOI: 10.1016/j.commatsci.2018.02.029

Molecular dynamics simulations were performed with a Finnis-Sinclair many-body potential to investigate the mechanical properties and deformation mechanisms under applied uniaxial tensile and compressive loads in alpha-titanium (Ti) single-crystal nanopillars oriented along the < 1 1 (2) over bar 0 > direction. The results indicate that the mechanical properties and plastic deformation mechanism display tension- compression asymmetry. The non-linear elastic behavior is attributed to the difference in friction between the neighboring atomic planes at the elastic deformation stage under push and pull loading conditions. Increasing the friction leads to hardening with compression. Decreasing the friction leads to softening with tension. Increasing the friction may also lead to higher yield stress with compression compared with tension. Perfect nanopillars are yielded via the nucleation and propagation of (1) over bar 0 1 0 < 1 (2) over bar 1 0 > dislocations on the surface and corners of the nanopillars. Prismatic slip is the dominant mode of plastic deformation in the Ti nanopillars under compressive loading. However, 1 0 (1) over bar 1 < 1 0 (1) over bar (2) over bar > twinning is the dominant plastic deformation mechanism together with prismatic slip under tensile loading. Two typical intrinsic stacking faults (SFs) with different propensities exist in the nanopillars. The microstructural evolution of the SFs was also simulated. (C) 2018 Elsevier B.V. All rights reserved.

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