| Micro-nano structure tantalum carbide(TaC)ceramic material was prepared by the in-situ reaction with the raw material of metal Ta plate and gray cast iron.The phase composition,microstructure and chemical composition of prepared TaC were studied by the X-Ray Diffraction(XRD),Scanning Electron Microscope(SEM)and Energy Dispersive Spectrometer(EDS).Then the hardness,elastic modulus and plastic deformation behavior of prepared TaC were measured by the methods of nano-indentation.Last the yield strengrth of prepared TaC was characterized by the methods of nano-indentation combining finite element simulation and dimensional analysis.The results show that:(1)Micro-nano structure TaC ceramic material can be prepared on the condition of holding under 1135℃ for some time and then cooled in water with the raw materials of tantalum plate and gray cast iron.The ceramic layer and matrix combines well without interface defect or impurity,showing the advantages of in-situ reaction.The thickness of TaC ceramic layer is about 25μm when the holding time is 10min.The TaC ceramic layer closing to Ta plate is compact and uniform,and it is nearly composed by TaC particle.But the closer the TaC ceramic layer away from the grey cast iron,the fewer of the TaC ceramic particles and the more of the content of Fe and C element.The XRD results show that there is only TaC phase in the surface of micro-nano structure TaC ceramic,which indicates that TaC particles are very compact closing to the surface of TaC ceramic layer.However,there are also Ta、TaC、Fe3C、α-Fe and flake graphite G phases in the vertical section of micro-nano structure TaC ceramic.(2)The hardness and elasticity modulus of micro-nano structure TaC ceramic material were studied by nano-indentation.In nano-indentation test,the intrinsic hardness and elasticity modulus of micro-nano structure TaC ceramic material with different indentation depth all obviously show the indentation size effect,that the hardness and elasticity modulus decrease gradually with increasing indentation size.Due to the effect of microstructure,the hardness and elasticity modulus decrease gradually with increasing penetration depth after the hardness/elasticity modulus-penetration depth curve presented a platform or peak value.So the hardness and elasticity modulus of micro-nano structure TaC ceramic material are not constant.TaC ceramic closing to the surface of sample is very compact,so the hardness and elasticity modulus with the depth of 300nm are taken as the intrinsic hardness and elasticity modulus of micro-nano structure TaC ceramic layer,which are 21GPa and 413GPa respectively.(1)The plastic deformation behavior of micro-nano structure TaC ceramic was studied by nano-indentation,it shows that the plastic deformation increase with the increase of load and loading rate.This conclusion was proved by analyzing creep stress index of material.The creep stress index decreases with the increase of load and loading rate.The smaller the creep stress index,the bigger the plastic deformation ability.(2)In the process of determining the yield strength of micro-nano structure TaC ceramic,firstly,the nano-indentation results were analyzed by Ⅱ theorem in dimension analysis.The dimensionless functional correlation between load-displacement curve which is gained in nano-indentation test and every parameter(yield strength,Poisson’s ratio and so on)of the material is obtained.Secondly,the process of nano-indentation press in 1000nm was simulated by finite element analysis and the specific functional form was obtained by dealing with the simulation data.Thirdly,the yield strength was determined by combining load-displacement curve obtained in nano-indentation test and the specific functional form,and the value of yield strength is 7.05GPa. |
PDF Full Text Request