Technology Design And Preparation Of Ceramic Cutting Tools Based On Simulation Of Microstructure Evolution

With the rise of our manufacturing industry,high-speed cutting have deemed to the focus of development,and the requirements for cutting tools have also increased.Ceramic tools have become one of the ideal choices for high-speed cutting due to their excellent mechanical properties.However,a lot of time is taken to optimize the sintering process when designing ceramic tools with the traditional "trial and error method",which delays to the replacement of ceramic tools.Through computer modeling,the microscopic and even nanoscopic microstructure evolution process of ceramic tool materials can be simulated for the design and preparation of ceramic tools,which saves manpower,material resources and material loss a large extent.The cellular automata method is a mathematical model that expresses the evolution process through the transformation of cells.That method has a high degree of randomness and the change trend can be guided through the change rule at the same time.It is easy to operate,the change direction can be determined,and the recognition error is less,which reflects the evolution process of the microstructure of ceramic tool materials.The main purpose of this thesis was to build a model which can reveal the influence of sintering process parameters on the evolution of the microstructure by improving the simulation method of the cellular automata model,and offer guide for the preparation of the ceramic tools with the SPS method.In the sintering process,the grain growth process is a complex process related to many factors.The mobility of the grain boundary is related to the absolute temperature;the grain size is related to the absolute time.The main influencing factors that affect the grain growth process are pores and sintering process parameters.Therefore,these influencing factors need to be considered in the simulation process of the microstructure evolution model of micro-nano composite ceramic tool materials.An improved cellular automata model was constructed to simulate the evolution of microstructure of micro-nano composite ceramic tool materials with pores,and a simulation system was established.The central cell state transition rule of the cellular automata model was improved,and the problem of abnormal grain boundary morphology in the simulation was solved.The assignment method of cell state value was improved,and the problem of abnormal growth of crystal grain recognition error was solved.The densification evolution process of grain microstructure of micro-nano composite ceramic tool materials was simulated,and a simulation system of the micro-nano composite ceramic tool material microstructure evolution was established based on the Visual Studio 2013 platform.The sintering parameters of the spark plasma sintering method was coupled into the constructed model,so that the influence of sintering parameters on the microstructure evolution of micro-nano composite ceramic tool materials could be reflected accurately.The expression of the sintering temperature factor was derived from the relationship between the absolute temperature and the sintering speed,and the sintering temperature factor was multiplied by the cell state transformation success probability P to couple the sintering temperature into the constructed model.The relationship between time step and actual time was derived from the parabolic law of isothermal grain growth,and the relationship was coupled into the time step calculation module,so that the holding time was coupled into the constructed model.The expression of the pressure factor was derived from the relationship between the axial compressive stress and the grain growth rate,and the pressure factor was multiplied by the success probability P of the central cell transformation to couple the sintering pressure into the constructed model.According to the evolution results of the constructed model,when the sintering temperature was 1600?,the holding time was 7min,and the sintering pressure was 40MPa,the grain size distribution of the ceramic tool material was more even,the pore content was lower,and the material density was higher.The preparation of ceramic tool materials according to this sintering process could obtain micro-nano composite ceramic tool materials with better macro-mechanical properties.Al2O3/TiB2/TiC micro-nano composite ceramic tools was prepared with the optimized sintering parameters obtained from the model.When the proportion of TiB2 was 20%and TiC was 10%,the mechanical properties were the best.And the hardness,fracture toughness and flexural strength were 20.3GPa,10.5MPa/m2 and 839.5MPa,respectively.In the preparation of Al2O3/TiB2/TiC micro-nano composite ceramic tool materials,when the sintering process parameters were the same as the optimized sintering process parameters,the mechanical properties are optimal.Analyzing specimen SEM photos,the evolution process of the microstructure of the micro-nano composite ceramic tool material can be reflect correctly by the constructed model.