The effect of grain size on the deformation mechanisms and mechanical properties of polycrystalline TiN: A molecular dynamics study

The uniaxial tensile mechanical properties of polycrystalline TiN with 14 different grain sizes measuring 2.0-5.8 nm were studied via molecular dynamics with the second-nearest-neighbour modified embedded-atom method (2NN MEAM). The results show that the grain size affects the movement mechanisms of the grains and grain boundaries, and the relationship between grain size and tensile yield strength. The direct and inverse Hall-Petch formula of TiN are given. The dislocation migration of grain boundaries is the main deformation mechanism when the grain size is larger than 3.2 nm. When grains are smaller than 3.2 nm, grain rotation and grain boundary sliding are the preferred deformation mechanisms, which cause an inverse Hall-Petch effect. Polycrystalline TiN is at its hardest when the grain size ranges from 3 to 4 nm. The results can serve as theoretical basis for further doping non-metallic elements with critical grain sizes in the grain boundary produce superhard TiN composites. (C) 2017 Elsevier B.V. All rights reserved.