The Study Of Simulation On Microstructure Evolution Of Al₂O₃/TiC Composite Ceramic Cutting Tool

Ceramic cutting tool material is widely used in high efficiency and precision machining process because of its high hardness,high-temperature resistance and wear resistance.However,its strength and fracture toughness are so low that the application range of ceramic tool materials is limited.The microstructure of materials play an important role in increasing its mechanical properties.Therefore,to simulate the process of the evolution of microstructure of ceramic materials can provide theoretical basis for the development of new ceramic tool materials.This paper studies the grain growth theory and the classical Monte Carlo algorithm and model,and improves the classical algorithm from the grain reorientation probability,boundary conditions and orientation method respectively.An improved algorithm of simulation program is developed and using MATLAB software to simulate the evolution of microstructure of ceramic tool materials under different parameters during the sintering process.The evolution of microstructure of Al2O3/TiC composite ceramic tool materials has been simulated based on the improved algorithm of simulation program.The effect of different content and size of TiC particles and the different initial size of the matrix phase in the evolution process have been simulated.The simulation results show that the pinning effect of the second phase TiC particles to the matrix phase can suppress the abnormal growth of the grain and refine the grain size.And the pinning effect of TiC particles increases with an increment in the content and smaller grain size of TiC particles.The smaller initial particle size of matrix phase helps to obtain the small-sized simulated microstructure for a given content and size of TiC particles.It can also increase the number of the second phase particles entering into the matrix phase increase,which is conducive to form an intragranular-type microstructure.The influence of sintering process parameters on microstructure evolution has been analysed and studied.The Monte Carlo Potts model that incorporated with sintering temperature and sintering pressure has been established.The simulation process is achieved and it is shown that the average grain size increases with the extension of the simulation time and the higher sintering temperature and sintering pressure.The paper also analyzes the residual stress field and toughening mechanism of composite ceramic tool materials and establishes the finite element simulation model.Through studing the effect of the volume ratio of the second phase on the residual stress field of the composite ceramic material,the results show that a larger volume ratio of the second phase particles within a certain range is conducive to improve the fracture toughness of the material.To control of the volume fraction of second phase particles reasonably and increase the residual stress can help to the toughening of the composite ceramic tool materials.Samples of Al₂O₃/TiC composite ceramic tool materials are prepared under different content and sintering process parameters by the hot-pressing sintering method.The mechanical properties of samples are measured and the fracture morphology images are observed through experiments.The images obtained from experiments accord with the microstructure evolution rules after compared with the simulation images.Therefore the improved models and algorithm of simulation program are verified by experiments.