| Ceramic tools are being widely used in the fields of high speed cutting and manufacturing due to their outstanding properties such as high hardness,high wear resistance,good high-temperature mechanical properties and chemical stability. However,the traditional ceramic tools fabrication methods have low efficiency and high research and development cost.Using computer simulation technology to simulate the fabrication process of ceramic tools has been proved to be an effective method to optimize the fabrication process,save the research cost and reduce the development cycle.The state of the art of material simulation technology is summarized and the simulating methods which are usually used in the nano-scale simulation are introduced in detail.The fabrication process of Al2O3 ceramic tools is simulated within the nano-scale(1-100nm) in the platform of Material Studio,using computer simulation technology based on the theories of quantum mechanics and molecular dynamics,and the simulating results are analyzed.The 3D simulation models of unitaryα-Al2O3 ceramic material system are simulated in the temperature of 300K,573K,873K,1173K,1473K and 1773K respectively,and the self-diffusion coefficients of the atoms in the system are analyzed through statistically calculating the mean square displacements of those atoms. According to the analyzing results,both of the self-diffusion coefficients of the elements O and Al keep rising to the summit at the temperature of about 1000K,and then go down as the temperature increases,but the self-diffusion coefficient of O is larger than that of Al.Therefore,around the temperature of 1000K,the sintering speed of the system is the fastest and the diffusion mechanism of the atoms in the system begins to change probably from surface diffusion to volume diffusion. The 3D simulation models ofα-Al2O3 ceramic material system adulterated with Si are established.Those models are simulated in the temperature of 300K,573K,873K, 1173K,1473K and 1773K respectively,and the diffusion coefficients of the atoms in the system are analyzed through statistically calculating the mean square displacements. According to the analyzing results,the existence of Si stimulates the activity of the atoms in the system,so that the sintering speed of the system is enhanced.The stimulation effect is more obvious to the element O than that to the element Al. Meanwhile,the diffusion coefficient of the element O keeps rising with the increase of temperature,because the existence of the element Si changes the original diffusion mechanism of the element O.But the existence of the element Si exerts little influence on the element Al,whose variation tendency of the diffusion coefficient does not change dramatically compared with that in the unitaryα-Al2O3 ceramic material system.The 3D simulation models ofα-Al2O3 ceramic material system adulterated with SiC are established.The mechanical properties,including elastic constants,Young's modulus and Poisson's ratios of unitaryα-Al2O3 ceramic material system,α-Al2O3 ceramic material system with vacancies andα-Al2O3 ceramic material system adulterated with SiC are calculated separately using CASTEP software package.The simulation results of the unitaryα-Al2O3 ceramic material system are compared with the actual parameters and the difference is around 10%,which justifies the feasibility of using quantum mechanics to predict the mechanical properties of materials.According to the simulation results of theα-Al2O3 ceramic material system with vacancies,the existence of the atom vacancies makes the mechanical properties of the system decrease, and the higher the vacancy rate is,the worse the mechanical properties are.Moreover, the vacancies formed by the element O have more influence on the mechanical properties than those formed by the element Al.According to the simulation results of theα-Al2O3 ceramic material system adulterated with SiC,the existence of SiC decreases the mechanical properties of the system,and some chemical reactions would probably happen between SiC andα-Al2O3. |
