MD simulations of loading rate dependence of detwinning deformation in nanocrystalline Ni

Abstract

Molecular dynamics simulations are performed to investigate the deformation behavior of nanocrystalline Ni with pre-twin atom structure. The simulation sample is composed of four grains with average size 12 nm. The simulation technique of isobaric-isothermal ensemble (NPT) with high pressure is applied to obtain a sample with two circle twins. Under uniaxial tensile and shear loading, as well as different detwinning deformation behaviors are observed. Under uniaxial tension the detwinning deformation is induced by the event of grain growth, and it is supported by local energy analysis. Under the shear loading the detwinning deformation is related to the loading rate. The results show that there may be a critical shear rate. As the shear rate is sufficiently high the circle twin is found to be failed; as the shear rate is less than that rate, the size of circle twin become smaller and gradually approach a constant value. Our simulation results are in good agreement with experiment observation.

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