Simulations Of Mechanical Behavior Of Nanocrystalline WC-Co Cemented Carbide At High Temperatures

Investigating the mechanical behavior and its microscopic mechanism of WC-Co cemented carbides under high temperatures is necessary on understanding the relationship between the microstructure and properties of cemented carbides.It would be of great scientific interest and helpful in designing and developing tool materials with high performance.However,due to the limitation in the current experimental techniques,systematic studies of the mechanical behavior and deformation mechanism of WC-Co cemented carbides,a typical metal-ceramic composite material,are still lacking.It is especially desired to quantitatively understand the mechanical behaviors of nanocrystalline WC-Co composites at high temperatures and its microscopic mechanism on atomic scale.In this study,molecular dynamics(MD)simulation method was used to establish the polycrystalline WC-Co composite model on atomic scale.The mechanical behavior of nanocrystalline cemented carbide at room temperature and high temperatures were studied with the increase of stress under uniaxial loading.The influences of grain boundary,defects in the grains and grain size on the plastic deformation mechanism at high temperatures were analyzed.The main contents and conclusions are as follows:Firstly,the nanocrystalline cemented carbide with a large grain size(13.0nm)was studied under the uniaxial compression.The variation of microstructure with temperature and stress was investigated,and the effect of the Peierls stress on the motion of dislocations in WC and Co was evaluated.The mechanism of the nucleation and propagation of microcracks under high temperatures has been revealed.It is found that,the sliding and migration of grain boundary,grain rotation combined with the movement of intragranular dislocations and stacking faults contribute to the plastic deformation of the nanocrystalline cemented carbide at high temperatures.Secondly,nanocrystalline cemented carbides with various grain sizes(5.97~15.05nm)were studied under uniaxial compressive loading at room and high temperatures.The evolution of atomic arrangement of nanocrystalline cemented carbides with temperature and grain size was analyzed,and the effect of grain size on the plastic deformation behavior of WC-Co cemented carbide was investigated.According to the simulation results,the strength and grain size of the composite follows the inverse Hall-Petch relationship within the simulated grain size range.It reveals the mechanism of plastic deformation of nanocrystalline cemented carbides.In summary,the effects of temperature and grain size on the mechanical behaviors of nanocrystalline WC-Co cemented carbide under uniaxial compression were studied by MD simulations in the present work.The formation and evolution of dislocationbased crystal defects during the compressive process were systematically analyzed.It may provide further understanding for the microscopic mechanism of the mechanical properties of WC-Co composites at high temperatures and new theoretical support for the experimental study and design for WC-Co cemented carbides.