The Molecular Dynamics Simulation Research On Interface Of Al₂O₃ Matrix Nano-ceramic Tool Materials

Using computer simulation technology, the microstructure evolution of nano-ceramic tool materials can be simulated to guide the design, fabrication and mechanical property research of ceamic tool materials. The research results are of important theoretical significance to develop novel ceramic tool materials.Based on the simulation platform of Material Studio, five kinds of Al2O3 surface models, such as the model with the outermost atoms of Al, the surface atom structure model ofα-Al2O3-AI(0112) with different of surface layer, and the surface atom structure model ofα-Al2O3-O(0112) with the outermost atoms of O, have been established in the thesis. The simulation are carried out using the CASTEP simulation module of quantum mechanics and the surface energy of various kinds of atom structure are calculated. The results show that the surfrace energy of theα-Al2O3-Al(0112) increases with an increment in the surface layer thickness, and get the maximum 1.76 J/m2 when the surface layer thickness is about 0.71 nm. The surfrace energy of theα-Al2O3-O(0112) is 3.35 J/m2 which is greater than that ofα-Al2O3-Al(0112) surface. Consequently, the surface ofα-Al2O3-Al(0112) is more stable. But the surface activity of oxygen element on the surface of theα-Al2O3-O(0112) is greater and thus the surface ofα-Al2O3-O(0112) can easily combine with the surface of another material and form stable interface.Four kinds of interface microstructure models, such asα-Al2O3(0001)/β-SiC(111),α-Al2O3(0112)/β-SiC(001),α-Al2O3(0112)/β-SiC(211) andα-Al2O3(0112)/β-SiC(310), have been established and simulated with molecular dynamics. The simulation results show that the order of the interfacial bonding energy for the four kinds of interfaces is α-Al2O3(0112)/β-SiC(310)>α-Al2O3(0112)/β-SiC(001)>α-Al2O3 (0001)/β-SiC(111)>α-Al2O3(0112)/β-SiC(211). The effect of the interfacial bonding energy on interfacial bonding strength is analyzed. It is shown that the interfacial bonding mode diversity can improve the interfacial bonding stability, and the more the number of interface bond, the greater the bonding energy and thus the higher the bonding strength. The interface stability and the interfacial bonding strength is getting better with the reduction of the interface deformation rate. And also during the process of the intergranular fracture, the crackes will easily propagate along the weak interface with a lower interfacial bonding energy and strength.The simulation results show that there is no liquid phase in the grain interface between Al2O3 and Al2O3, and the phase interface between Al2O3 and SiC of the material Al2O3/SiC. The crystal lattice of two adjacent grains is well matching each other, and the interface bonding status between Al2O3 and SiC is better and the interfacial bonding energy and bonding strength is higher. Thus the fracture mode of Al2O3/SiC is intragranular fracture. These results are in well agreement with the previous research results of Al2O3/SiC by other researchers and verify the validity of the established models in the thesis on certain extent.