Effects of strain rate and annealing temperature on tensile properties of nanocrystalline diamond

C Huang and XH Peng and B Yang and X Chen and QB Li and DQ Yin and T Fu, CARBON, 136, 320-328 (2018).

DOI: 10.1016/j.carbon.2018.04.052

Nanocrystalline diamond (NCD) is a promising material due to its extraordinary properties, such as ultrahigh strength and hardness. The effects of strain rate (<(epsilon)over dot>) and annealing temperature (T-A) on the tensile properties of a NCD sample were investigated using molecular dynamics (MD) simulations. The anisotropy ratio of the sample was used to indicate the anisotropic nature of a polycrystalline, and the T-A less affect the anisotropy ratio. The failure stress, strain and deformation work density increase with the increase of <(epsilon)over dot> in power forms, and mainly show an upward trend with the increase of T-A. The loading at 5E8/s < <(epsilon)over dot> < 5E9/s can be regarded as quasi-static loading. The effect of <(epsilon)over dot> can be attributed to that lower <(epsilon)over dot> may provide longer time for the relaxation of local residual stress and the energy released may compensate for the deformation work or reduce the external energy needed for further deformation. The effect of T-A should result from the rearrangement and stabilization of grain boundaries. For samples annealed at different T-A and strained at different <(epsilon)over dot>, nucleation and propagation of both transgranular and intergranular cracks are the main failure mechanism of the NCD under tension, and no apparent plastic deformation can be detected. (C) 2018 Elsevier Ltd. All rights reserved.

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