Study Of Crystalline Dislocation Motions Using Phase Field Crystals

The phase field crystal model is a new method of simulating microstructure evolution on interatomic length scales and diffusive time scales. The model incorporates elastic and plastic deformation in a natural manner, and enables access to time scales much lager than conventional molecular dynamics simulation. The method has great advantages in the field of the kinetics of crystal defects. One-dimensional defects is known as the dislocations in polycrystalline materials. They have significant influence on the mechanical properties of the materials. This thesis uses two-mode phase field crystal model to simulate the dis-location motions of symmetric and asymmetric tilt grain boundary with two-dimensional square lattice in deformation processes.The thesis simulates the defects motion of fcc lat-tice. Main contents and results are as follows:1. Design2D symmetrical tilt grain boundaries which are made up of parallel edge dislocaions. The simulation results show:The desity of dislocations is mainly affected by orientation; Tensile stress causes negative climb, conversely compressive stress causes positive climb; Higher temperature is conductive to dislocation climb.2. An edge dislocation can react to form three edge dislocations by uniform deforma-tion. One of the newly generated edge dislocations climb through the grain boundary, the others climb into grains in oppsite directions.3. Design2D asymmetrical tilt grain boundaries with double-array dislocations and edge dislocaions with a vertical distribution. There are four dislocation reactions in the process of deformation.4. Simulate the defect motions of fcc lattice. The result show that the stress direction can not change the direction of defect motions, and the tensile stress is favorable to the defect motions.The results can guide the development of material experiment.