Study On Sintering Preparation And Mechanical Properties Of C Vacancy Induced Diffusion Type High Entropy Ceramic Hard Materials

In this paper,TiC_0.5 vacant raw materials are used as the main body.First,studying the influence of diffusion driving temperature on the diffusion behavior of the two diffusion couples of TiC_0.5-VC and TiC_0.5-NbC,and the diffusion behavior of metal atoms in TiC_0.5 at different concentrations.Then,on the basis of its diffusion theory,through the SPS sintering technology,the effect of sintering temperature on the phase,grain micromorphology,comprehensive mechanical properties and diffusion degree of high-entropy ceramic hard materials with different components is further studied.Finally,the high-temperature and high-pressure synthesis technology is used to improve the comprehensive mechanical properties of high-entropy ceramics with different components,and the effect of holding time on its properties is also studied.The experiment used X-ray diffraction?XRD?,scanning electron microscope?SEM?,X-ray energy spectroscopy?EDS?,universal testing machine,microhardness tester,and density testing equipment to analyze and characterize the phase and grain micromorphology,diffusion behavior and comprehensive mechanical properties of the sintered body under different experimental conditions.The experimental results show that:1)In the two sets of diffusion couples(TiC_0.5-VC,TiC_0.5-NbC),V atom exhibits a more temperature-sensitive diffusion behavior,and its diffusion coefficient increases sharply at 1700?,on the order of 10^-14.The diffusion coefficient of Nb atoms in TiC_0.5 gradually increases with increasing temperature,but the increase is relatively small,and the changes in diffusion coefficient caused by the two temperature gradients are within the same order of magnitude.The diffusion coefficients of V and Nb atoms in TiC_0.5 decrease gradually with the increase of concentration,but the decrease is very small.The frequency factor and diffusion activation energy of V atoms in TiC_0.5 are consistent with the increase of V atom concentration,and they both gradually decrease.However,the frequency factor and diffusion activation energy of Nb atoms in TiC_0.5 have an opposite change trend with the increase of Nb atom concentration,the frequency factor gradually decreases,and the diffusion activation energy gradually increases.2)Using SPS sintering technology,three high-entropy ceramics can obtain a single high-entropy ceramic phase at 1600?sintering temperature,while the control experiment using TiC instead of TiC_0.5 did not obtain the desired single phase under the same conditions.The three-component high-entropy ceramics also obtained a single phase under sintering conditions of 1500?,but the mechanical properties and the degree of diffusion were poor.Five-component high-entropy ceramics,due to the introduction of metal atoms Ta with a larger atomic radius,exhibit a phenomenon that the phase diffraction peak shifts to a high angle with increasing temperature,and it achieves better mechanical properties at higher sintering temperatures.Mechanical properties.The micro-hardness and fracture toughness of high-entropy ceramics with different components reached21.3 GPa and 7.12 MPa·m^1/2 at higher temperatures,while the bending strength was relatively low.3)Under high-pressure conditions,the high-entropy ceramic sintered body is denser and has fewer pores.Its micro-hardness,bending strength and fracture toughness all show different degrees of improvement.Among them,the flexural strength increased more.Except for the three-component high-entropy ceramics,the flexural strength gradually increased with the increase of the holding time,while the three-component high-entropy ceramics increased first and then decreased with the increase of the holding time.The maximum is reached at 20 minutes,and the five-component high-entropy ceramic has the highest bending strength,which is 438MPa.The porosity of the three high-entropy ceramics under high-pressure conditions is significantly lower than that of SPS sintering,with the lowest being 0.10%,0.128%and 0.122%.