Phase Field Crystal Simulation Of Vacancy Configuration And Its Evolutiong

The properties of nanostructure metallic materials are depended on the microstructure of materials. Knowing well the nanostructure metallic materials microstructure and the defects (vacancies and dislocations), grain boundary as well as the grain size of the crystalline are greatly helpful of understanding the mechanism of plastic deformation of nanostructure metallic materials. Dislocations are the core role of the plastic deformation mechanism to nanostructure metallic materials. The vacancies also can become the role when the grain size of nanostructure metallic materials is very small only a few nanometers. Due to the grain size is very small, it is difficult for us to observe the details of the plastic deformation in experimental conditions. Fortunately the computing simulation can make up the defective of the experiment. The latest modeling techniques who is named phase field crystal model has been widely applied in the field of crystalline structure. Moreover it is helpful making vacancy and dislocation as exploring plastic deformation mechanism. Therefore, in this paper, we use the modified phase field crystal model to study the two-dimensional periodic crystal morphology expressing in different crystal phases in the first time. Moreover, it discusses the effects different temperature and stress on the vacancy concentration of monocrystalline and polycrystalline, which is in order to help reveal behavior of the vacancy evolution in the process of plastic deformation in nanostructure metallic materials, as well as discusses the regulations. The main conclusions as follows:1. By selecting the average atomic density values of different phases which are appearing the different morphologies of two-dimensional periodic crystal structures, for example, Hex Bumps, Stripes and Hex Holes. When the average atomic density values of the system are sufficiently small, the system can generate vacancies; when the average atomic density values is suitable for the system, it can get the coexist phase topographies. These topographies can be used to interpret the topography of nano-films in laboratorial experiments.2. Whether monocrystalline and poly crystalline system, the temperature is greatly influence on the vacancy concentration, as well as presents the different topographies in the system. The higher temperature of their environment is the more vacancy concentration of the steady state in the system. But the vacancy concentration is maintaining at magnitude in 10-3～10-4.When the system environment is higher, the time which required for the system arise vacancies is shorter and the speed of vacancy formation of the system is faster. It proves that the vacancy concentration and temperature have a great relationship.3. In the same growth environment, the concentration vacancies of the monocrystalline is smaller than polycrystalline. Due to the grain boundaries, polycrystalline is more conducive to form vacancy. So the vacancy will choose to grow around dislocations in the grain boundary at first. For monocrystalline, there are only vacancies presenting in the steady state. But for polycrystalline, it consists not only vacancies but also vacancy clusters when the crystal reaches steady state.4. Whether it is monocrystalline or polycrystalline, the vacancy will again appear under the compressive stress. The number of vacancies by compressive stress is larger than environmental. The compressive stress values which is making vacancy appear of polycrystalline system is less than the monocrystalline system.The above study is looking forward to reveal the plastic deformation behavior of vacancy by using phase field crystal, which is further exploring to the regulation of its function, what is more, it is helpful that the model apply to a specific material in the future.